#986: add Blender scene export for 3D Camera Tracker

contributors/people.toml

@@ -17,6 +17,9 @@
 # To remove your names, delete your entry (or set fields empty) in a PR. The next
 # contributors.py run, and the next build, drop them.
 
+[people.Krueels]
+sync_github_name = true
+
 [people.echelon]
 real_name = "Brandon Thomas"
 display_name = "Brandon Thomas"

crates/engine/src/cmd.rs

@@ -10,6 +10,7 @@ mod animation;
 pub(crate) mod app_more;
 mod autotrace;
 mod batch;
+mod blender;
 mod camera_cmds;
 mod comp;
 pub(crate) mod comp_more;

crates/engine/src/cmd/blender.rs

@@ -0,0 +1,295 @@
+//! Camera-solve interchange through Blender's public Python API. The generated script is
+//! original MIT OR Apache-2.0 code; no Blender implementation is read or embedded.
+
+use std::path::Path;
+
+use effectcraft_effects::camera_tracker as ct;
+use effectcraft_project::{Footage, FootageKind, ItemId, ItemKind, Layer, LayerId, LayerSource, Uid};
+use effectcraft_render::EvalCtx;
+use effectcraft_time::Tick;
+use effectcraft_track::camtrack::{CameraSolve, linalg};
+use serde_json::{Value, json};
+
+mod validate;
+
+use super::{b_p, bad, f_p, str_p};
+use crate::{EngineError, Result, Session};
+
+const CMD: &str = "camera.exportBlender";
+const MAX_FRAMES: usize = 100_000;
+const MAX_POINTS: usize = 100_000;
+const MAX_JSON: usize = 64 * 1024 * 1024;
+const MAX_FRAME: i64 = 1_048_574;
+
+fn number(p: &Value, key: &str, default: f64, min: f64, max: f64) -> Result<f64> {
+    let v = match p.get(key) {
+        None => default,
+        Some(_) => f_p(p, key).ok_or_else(|| bad(CMD, format!("{key}: expected a number")))?,
+    };
+    if !v.is_finite() || !(min..=max).contains(&v) {
+        return Err(bad(CMD, format!("{key}: expected {min}..{max}")));
+    }
+    Ok(v)
+}
+
+fn finite(values: impl IntoIterator<Item = f64>) -> Result<()> {
+    if values.into_iter().any(|v| !v.is_finite() || v.abs() > 1e12) {
+        return Err(bad(CMD, "invalid or excessive numeric camera/scene data; re-analyze the tracker"));
+    }
+    Ok(())
+}
+
+/// Right-handed EffectCraft world (right, down, forward) → Blender (right, forward, up).
+fn position(p: [f64; 3], scale: f64) -> [f64; 3] {
+    [p[0] * scale, p[2] * scale, -p[1] * scale]
+}
+
+fn media_path(s: &Session, path: &str) -> Result<String> {
+    if path.is_empty() || path.contains('\0') {
+        return Err(bad(CMD, "the source footage has no valid file path; relink it before exporting"));
+    }
+    let path = Path::new(path);
+    if path.is_absolute() || cfg!(target_arch = "wasm32") {
+        return Ok(path.to_string_lossy().into_owned());
+    }
+    let cwd = std::env::current_dir().map_err(|e| bad(CMD, format!("cannot resolve footage path: {e}")))?;
+    let base = s.path.as_deref().and_then(|p| Path::new(p).parent()).map(|p| cwd.join(p)).unwrap_or(cwd);
+    Ok(base.join(path).to_string_lossy().into_owned())
+}
+
+pub(super) fn export(s: &mut Session, p: &Value, cid: ItemId, lid: LayerId, uid: Uid) -> Result<Value> {
+    if s.running_for_script() && !s.prefs.scripting.allow_scripts_write_files {
+        return Err(bad(CMD, "scripts can't export files unless Settings ▸ Scripting & Expressions ▸ Allow Scripts to Write Files and Access Network is on"));
+    }
+    let options = Options::parse(p)?;
+    let Options { path, sensor, units, start, include_points } = options;
+    if s.camera_target().is_some_and(|(c, l, u)| (c, l, u) == (cid, lid, uid)) && s.is_camera_analyzing() || s.camera_pending.contains(&(cid, lid, uid)) {
+        return Err(bad(CMD, "wait for this tracker's analysis to finish before exporting"));
+    }
+    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
+    let layer = comp.layer(lid).ok_or_else(|| bad(CMD, "tracked layer missing"))?;
+    let g = layer.props.find_group(uid).ok_or_else(|| bad(CMD, "tracker missing"))?;
+    for name in [ct::SOLVE, ct::TRACKS] {
+        if g.prop(name).is_some_and(|p| matches!(&p.value, effectcraft_keyframe::Value::Str(v) if v.len() > MAX_JSON)) {
+            return Err(bad(CMD, "tracking data exceeds the 64 MiB export limit"));
+        }
+    }
+    let params = crate::camera_track::static_params(g);
+    let solve = ct::solve(&params).ok_or_else(|| bad(CMD, "the camera is not solved yet; analyze the tracker first"))?;
+    let (lo, end) = validate::timing(comp, layer, &solve, start)?;
+    let Source { footage, path: source_path, fps: source_fps, count: source_count } = source(s, layer, &solve, path)?;
+    validate::geometry(&solve, sensor)?;
+    let camera = params
+        .get(ct::CAMERA)
+        .map(|v| v.as_f64())
+        .filter(|v| v.is_finite() && *v > 0.0 && *v <= u64::MAX as f64)
+        .and_then(|id| comp.layer(LayerId(id as u64)))
+        .filter(|l| l.is_camera());
+    let warnings = scene_warnings(camera, &solve, footage);
+    let ctx = EvalCtx { expr: s.expr.as_deref(), ..EvalCtx::new(&s.project, cid, comp, lo) };
+    let (frames, world) = bake_frames(&ctx, layer, &solve, camera, &options, footage, source_count)?;
+    let mut points = Vec::new();
+    for point in &solve.points {
+        finite(point.pos.into_iter().chain([point.error as f64]))?;
+        if point.first > point.last || point.last as usize >= solve.frames.len() {
+            return Err(bad(CMD, "invalid solved point frame range; re-analyze the tracker"));
+        }
+        let location = position(world.apply(point.pos), units);
+        finite(location)?;
+        if include_points {
+            points.push(json!({"id": point.id, "location": location, "error": point.error,
+                "first": start.saturating_add(point.first as i64), "last": start.saturating_add(point.last as i64)}));
+        }
+    }
+    let tracks = ct::tracks(&params);
+    if tracks.as_ref().is_some_and(|t| t.tracks.len() > MAX_POINTS || t.tracks.iter().any(|t| t.pts.len() > MAX_FRAMES)) {
+        return Err(bad(CMD, "2D tracks exceed export limits"));
+    }
+    let markers: Vec<Value> = comp
+        .markers
+        .iter()
+        .filter_map(|m| {
+            let frame = start.saturating_add(comp.frame_rate.frame_at(m.time).saturating_sub(comp.frame_rate.frame_at(lo)));
+            if (start..=end).contains(&frame) { Some(json!({"name": m.comment, "frame": frame})) } else { None }
+        })
+        .collect();
+    let payload = json!({"version": 1, "name": format!("{} — {}", s.project.item(cid).map(|i| i.name.as_str()).unwrap_or("Shot"), layer.name),
+        "resolution": solve.size, "fpsNumerator": comp.frame_rate.num, "fpsDenominator": comp.frame_rate.den,
+        "startFrame": start, "endFrame": end, "sensorWidth": sensor, "unitScale": units,
+        "media": {"path": source_path, "kind": if footage.kind == FootageKind::Still {"FILE"} else {"MOVIE"},
+            "fps": source_fps, "nativeRate": footage.native_rate, "pixelAspect": footage.pixel_aspect, "timecode": footage.start_timecode,
+            "frameCount": source_count, "loopCount": footage.loop_count},
+        "frames": frames, "points": points, "markers": markers, "ground": solve.ground.is_some(),
+        "groundSize": world.s * units, "shutter": comp.shutter_angle / 360.0, "shutterPhase": comp.shutter_phase,
+        "solve": solve, "tracks": if include_points { tracks.as_deref() } else { None },
+        "warnings": warnings});
+    let data = serde_json::to_string(&payload).map_err(|e| bad(CMD, format!("cannot serialize scene: {e}")))?;
+    if data.len() > MAX_JSON {
+        return Err(bad(CMD, "scene exceeds the 64 MiB script limit; disable includePoints or split the shot"));
+    }
+    let quoted = serde_json::to_string(&data).map_err(|e| bad(CMD, format!("cannot encode scene: {e}")))?;
+    let script = include_str!("blender_scene.py").replace("__EFFECTCRAFT_DATA__", &quoted);
+    s.services.write_file(path, script.as_bytes()).map_err(|e| bad(CMD, format!("cannot write {path}: {e}")))?;
+    Ok(json!({"path": path, "bytes": script.len(), "frames": frames.len(), "points": points.len(), "warnings": warnings}))
+}
+
+struct Options<'a> {
+    path: &'a str,
+    sensor: f64,
+    units: f64,
+    start: i64,
+    include_points: bool,
+}
+
+impl<'a> Options<'a> {
+    fn parse(p: &'a Value) -> Result<Self> {
+        let path = str_p(p, "path").filter(|p| !p.is_empty() && !p.contains('\0')).ok_or_else(|| bad(CMD, "missing `path` (.py)"))?;
+        if !Path::new(path).extension().is_some_and(|e| e.eq_ignore_ascii_case("py")) {
+            return Err(bad(CMD, "the export path must end in .py"));
+        }
+        let sensor = number(p, "sensorWidth", 36.0, 1.0, 1000.0)?;
+        let units = number(p, "unitScale", 0.01, 0.000_001, 1000.0)?;
+        let start = match p.get("startFrame") {
+            None => 1,
+            Some(v) => v.as_i64().filter(|n| (1..=MAX_FRAME).contains(n)).ok_or_else(|| bad(CMD, "startFrame: expected a positive Blender frame number"))?,
+        };
+        let include_points = match p.get("includePoints") {
+            Some(v) if !v.is_boolean() => return Err(bad(CMD, "includePoints: expected a boolean")),
+            _ => b_p(p, "includePoints").unwrap_or(true),
+        };
+        Ok(Self { path, sensor, units, start, include_points })
+    }
+}
+
+struct Source<'a> {
+    footage: &'a Footage,
+    path: String,
+    fps: f64,
+    count: i64,
+}
+
+fn source<'a>(s: &'a Session, layer: &Layer, solve: &CameraSolve, path: &str) -> Result<Source<'a>> {
+    let footage = match layer.source {
+        LayerSource::Footage { item } => s.project.item(item).and_then(|i| match &i.kind {
+            ItemKind::Footage(f) => Some(f),
+            _ => None,
+        }),
+        _ => None,
+    }
+    .filter(|f| f.has_video && matches!(f.kind, FootageKind::Video | FootageKind::Still));
+    let footage = footage
+        .ok_or_else(|| bad(CMD, "Blender background export needs a video or still-footage layer; render precomps/sequences to a video and track that video"))?;
+    let source_path = media_path(s, &footage.path)?;
+    if Path::new(path) == Path::new(&source_path) {
+        return Err(bad(CMD, "the export path must differ from the source footage"));
+    }
+    if footage.width as f64 != solve.size[0] || footage.height as f64 != solve.size[1] {
+        return Err(bad(CMD, "the analysis image differs from the original footage dimensions; render the tracker's input to a video and track that video"));
+    }
+    let source_fps = footage.frame_rate.as_f64();
+    if footage.frame_rate.num <= 0 || footage.frame_rate.den <= 0 || !source_fps.is_finite() || source_fps <= 0.0 {
+        return Err(bad(CMD, "invalid source footage frame rate"));
+    }
+    // Same frame selection as the media pool: interpreted FPS, rounded per-loop frame count,
+    // clamp to the total loop range, then wrap. Native FPS does not change the frame index.
+    let divisor = (effectcraft_time::TICKS_PER_SECOND as i128).saturating_mul(footage.frame_rate.den as i128);
+    let source_count = (footage.duration.0 as i128).saturating_mul(footage.frame_rate.num as i128).saturating_add(divisor / 2) / divisor;
+    let source_count = if footage.kind == FootageKind::Still { 1 } else { source_count };
+    if !(1..=MAX_FRAME as i128).contains(&source_count) {
+        return Err(bad(CMD, "invalid footage duration or footage exceeds Blender's frame range; trim/render the source video first"));
+    }
+    let source_count = source_count as i64;
+    Ok(Source { footage, path: source_path, fps: source_fps, count: source_count })
+}
+
+fn scene_warnings(camera: Option<&Layer>, solve: &CameraSolve, footage: &Footage) -> Vec<String> {
+    let mut warnings = vec![
+        "Sensor width is assumed (36 mm by default); monocular tracking cannot recover physical sensor size or absolute scene scale.".to_string(),
+        "The original footage is referenced, not embedded or rendered: masks and effects before the tracker are not baked. Relink the video if moving this script.".to_string(),
+    ];
+    if camera.is_none() {
+        warnings
+            .push("No linked tracker camera: focus uses the default scene depth, DOF is off; optical focus cannot be recovered from feature tracks.".into());
+    } else {
+        warnings.push("Focus/iris settings are sampled from the linked camera; pose and lens come from the tracker solve. Blender's physical DOF is an approximation of EffectCraft's blur model.".into());
+    }
+    if solve.distortion.is_some_and(|d| !d.is_none()) {
+        warnings.push("Radial distortion is preserved as metadata (Brown k1/k2, half-diagonal normalization), not applied to Blender's pinhole camera. Use an undistorted plate for exact alignment.".into());
+    }
+    if (footage.pixel_aspect - 1.0).abs() > 1e-6 {
+        warnings.push("The tracker solves square pixels: export uses square pixels; original footage pixel aspect is retained in metadata.".into());
+    }
+    warnings
+}
+
+/// Bake the solved camera and the linked camera's optical settings at exact composition ticks.
+fn bake_frames(
+    ctx0: &EvalCtx<'_>,
+    layer: &Layer,
+    solve: &CameraSolve,
+    camera: Option<&Layer>,
+    options: &Options<'_>,
+    footage: &Footage,
+    source_count: i64,
+) -> Result<(Vec<Value>, linalg::Similarity)> {
+    let comp = ctx0.comp;
+    let lo = ctx0.time;
+    let fd = comp.frame_duration();
+    let sensor = options.sensor;
+    let units = options.units;
+    let start = options.start;
+    let first = solve.frames.first().ok_or_else(|| bad(CMD, "the camera solve is empty"))?;
+    let m = ctx0.world_matrix(layer).0;
+    let layer_scale = m[0][0].hypot(m[1][0]);
+    finite([layer_scale])?;
+    if layer_scale <= 1e-9 {
+        return Err(bad(CMD, "the tracked layer has zero scale"));
+    }
+    let world = solve.world([comp.width as f64, comp.height as f64], first.focal * layer_scale);
+    finite([world.s * units])?;
+    let mut frames = Vec::with_capacity(solve.frames.len());
+    for (i, frame) in solve.frames.iter().enumerate() {
+        let time = Tick(lo.0.saturating_add(fd.0.saturating_mul(i as i64)));
+        let ctx = ctx0.at(time);
+        let pose = linalg::mm(&world.r, &linalg::mt(&frame.r()));
+        let right = position(linalg::mv(&pose, [1.0, 0.0, 0.0]), 1.0);
+        let up = position(linalg::mv(&pose, [0.0, -1.0, 0.0]), 1.0);
+        let back = position(linalg::mv(&pose, [0.0, 0.0, -1.0]), 1.0);
+        let location = position(world.apply(frame.center), units);
+        let lens = frame.focal * sensor / solve.size[0];
+        let opts = camera.and_then(|l| l.props.sub("cameraOptions").map(|g| (l, g)));
+        let value = |key: &str, fallback: f64| opts.map(|(l, g)| ctx.f(l, g, key, fallback)).unwrap_or(fallback);
+        let focus = value("focusDistance", world.s) * units;
+        let aperture = value("aperture", 0.0);
+        let zoom = value("zoom", frame.focal * layer_scale);
+        // Match Camera Settings' f-stop conversion: focal_for_zoom uses a 36 mm film width,
+        // and the aperture UI is mm scaled by comp_width / 1920 (not a world-space diameter).
+        let aperture_mm = aperture * 1920.0 / comp.width as f64;
+        let fstop = if aperture_mm > 0.0 { (zoom * 36.0 / comp.width as f64) / aperture_mm } else { 2.8 };
+        let rotation = value("irisRotation", 0.0).to_radians();
+        let ratio = value("irisAspectRatio", 1.0);
+        let shape = opts.map(|(l, g)| ctx.e(l, g, "irisShape")).unwrap_or(0);
+        let blades = match shape {
+            0 => 4,
+            1..=8 => shape.saturating_add(2),
+            _ => return Err(bad(CMD, "invalid iris shape")),
+        };
+        let dof = opts.is_some_and(|(l, g)| ctx.b(l, g, "dof")) && aperture > 0.0 && value("blurLevel", 100.0) > 0.0;
+        let source_time = ctx.source_time(layer);
+        let source_frame = if footage.kind == FootageKind::Still {
+            0
+        } else {
+            footage.frame_rate.frame_at(source_time).clamp(0, source_count.saturating_mul(footage.loop_count.max(1) as i64).saturating_sub(1)) % source_count
+        };
+        finite(location.into_iter().chain([focus, aperture, zoom, fstop, rotation, ratio, value("blurLevel", 100.0), value("irisRoundness", 0.0)]))?;
+        if focus <= 0.0 || !(0.01..=100.0).contains(&ratio) || !(0.01..=1e6).contains(&fstop) {
+            return Err(bad(CMD, "focus, f-stop or iris aspect is outside Blender's supported range"));
+        }
+        frames.push(json!({"frame": start + i as i64, "timeTicks": time.0, "sourceFrame": source_frame,
+            "location": location, "rotation": [right, up, back], "lens": lens, "focus": focus, "dof": dof,
+            "fstop": fstop, "blades": blades, "irisRotation": rotation, "irisRatio": ratio,
+            "sourceAperture": aperture, "sourceZoom": zoom,
+            "blurLevel": value("blurLevel", 100.0), "irisRoundness": value("irisRoundness", 0.0)}));
+    }
+    Ok((frames, world))
+}

crates/engine/src/cmd/blender/validate.rs

@@ -0,0 +1,71 @@
+//! Validate solved geometry and its correspondence to the current layer timing.
+
+use effectcraft_project::{Comp, Layer};
+use effectcraft_time::Tick;
+use effectcraft_track::camtrack::{CameraSolve, linalg};
+
+use super::{CMD, MAX_FRAME, MAX_FRAMES, MAX_POINTS, bad, finite};
+use crate::Result;
+
+pub(super) fn timing(comp: &Comp, layer: &Layer, solve: &CameraSolve, start: i64) -> Result<(Tick, i64)> {
+    if solve.frames.len() > MAX_FRAMES || solve.points.len() > MAX_POINTS {
+        return Err(bad(CMD, "export is limited to 100,000 frames and 100,000 points; split the shot"));
+    }
+    if solve.size.iter().any(|v| !v.is_finite() || *v < 4.0 || *v > 65_536.0 || v.fract() != 0.0) {
+        return Err(bad(CMD, "invalid tracking resolution (expected 4..65536 whole pixels)"));
+    }
+    let fps = comp.frame_rate.as_f64();
+    if comp.frame_rate.num <= 0 || comp.frame_rate.den <= 0 || !fps.is_finite() || !(1.0..=1000.0).contains(&fps) {
+        return Err(bad(CMD, "invalid composition frame rate (expected 1..1000 fps)"));
+    }
+    let end = start
+        .checked_add(solve.frames.len() as i64)
+        .and_then(|n| n.checked_sub(1))
+        .filter(|n| *n <= MAX_FRAME)
+        .ok_or_else(|| bad(CMD, "the baked animation exceeds Blender's frame range"))?;
+    finite([solve.start, solve.frame_duration, solve.average_error, layer.stretch, comp.shutter_angle, comp.shutter_phase])?;
+    if layer.stretch == 0.0 || comp.width == 0 || comp.height == 0 {
+        return Err(bad(CMD, "invalid composition dimensions or zero layer stretch"));
+    }
+    let lo = comp.frame_rate.snap_nearest(layer.in_point.max(Tick::ZERO));
+    let hi = layer.out_point.min(comp.duration);
+    let fd = comp.frame_duration();
+    if fd.0 <= 0 || lo >= hi {
+        return Err(bad(CMD, "the tracked layer has no active frames"));
+    }
+    let expected = ((hi.0 as i128 - lo.0 as i128 + fd.0 as i128 - 1) / fd.0 as i128) as u128;
+    if expected != solve.frames.len() as u128 {
+        return Err(bad(CMD, "the solve no longer matches the layer's frame range; re-analyze the tracker"));
+    }
+    let dt = (layer.layer_time(lo + fd) - layer.layer_time(lo)).seconds();
+    if (solve.start - layer.layer_time(lo).seconds()).abs() > 1e-6 || solve.frames.len() > 1 && (solve.frame_duration - dt).abs() > 1e-6 {
+        return Err(bad(CMD, "the solve no longer matches the layer's timing; re-analyze the tracker"));
+    }
+    Ok((lo, end))
+}
+
+pub(super) fn geometry(solve: &CameraSolve, sensor: f64) -> Result<()> {
+    for frame in &solve.frames {
+        finite(frame.rot.into_iter().chain(frame.center).chain([frame.focal]))?;
+        if !frame.solved || frame.focal <= 0.0 {
+            return Err(bad(CMD, "the solve contains unsolved frames or invalid focal lengths; re-analyze the tracker"));
+        }
+        let mm = sensor * frame.focal / solve.size[0];
+        if !(1.0..=5000.0).contains(&mm) {
+            return Err(bad(CMD, "lens outside Blender's 1..5000 mm range; choose another sensorWidth"));
+        }
+    }
+    if let Some(ground) = &solve.ground {
+        finite(ground.origin.into_iter().chain(ground.normal).chain(ground.x_axis))?;
+        if (linalg::norm(ground.normal) - 1.0).abs() > 1e-4
+            || (linalg::norm(ground.x_axis) - 1.0).abs() > 1e-4
+            || linalg::dot(ground.normal, ground.x_axis).abs() > 1e-4
+        {
+            return Err(bad(CMD, "invalid ground-plane basis; set the ground plane again"));
+        }
+    }
+    if let Some(d) = &solve.distortion {
+        finite([d.k1, d.k2, d.radius])?;
+    }
+    Ok(())
+}

crates/engine/src/cmd/blender_scene.py

@@ -0,0 +1,206 @@
+# EffectCraft camera tracker → Blender, original code under MIT OR Apache-2.0.
+# Blender scene export contributor: Krueels — https://github.com/Krueels
+# Run in Blender's Scripting workspace (Open, Run Script), or:
+# blender --background --python "Tracked Scene.py"
+# Creates a NEW scene; existing scenes and objects are preserved. Save the .blend yourself.
+# Public API references: https://docs.blender.org/api/4.5/bpy.types.Camera.html
+# https://docs.blender.org/api/4.5/bpy.types.ImageUser.html
+import json
+import math
+import os
+
+import bpy
+from mathutils import Matrix
+
+DATA = json.loads(__EFFECTCRAFT_DATA__)
+
+
+def _curves(owner):
+    """Blender 4.0–4.3 legacy actions and 4.4+/5.x layered actions."""
+    anim = owner.animation_data
+    if anim is None or anim.action is None:
+        return
+    action = anim.action
+    if getattr(action, "is_action_layered", False):
+        for layer in action.layers:
+            for strip in layer.strips:
+                if strip.type == 'KEYFRAME':
+                    bag = strip.channelbag(anim.action_slot)
+                    if bag is not None:
+                        yield from bag.fcurves
+    else:
+        yield from action.fcurves
+
+
+def _interpolation(owner):
+    for curve in _curves(owner):
+        # Footage indices and discrete switches must never interpolate between frames.
+        stepped = ("frame_offset" in curve.data_path or "use_dof" in curve.data_path
+                   or "aperture_blades" in curve.data_path)
+        for key in curve.keyframe_points:
+            key.interpolation = 'CONSTANT' if stepped else 'LINEAR'
+
+
+def _media_path():
+    original = DATA["media"]["path"]
+    candidates = [original]
+    # When sharing, place the video alongside the script or the .blend and run again.
+    script_path = globals().get("__file__", "")
+    if script_path:
+        candidates.append(os.path.join(os.path.dirname(os.path.abspath(script_path)),
+                                       os.path.basename(original)))
+    if bpy.data.filepath:
+        candidates.append(os.path.join(os.path.dirname(bpy.data.filepath),
+                                       os.path.basename(original)))
+    return next((p for p in candidates if os.path.isfile(p)), None)
+
+
+def import_scene():
+    if bpy.app.version < (4, 0, 0):
+        raise RuntimeError("EffectCraft scene import requires Blender 4.0 or newer")
+    scene = bpy.data.scenes.new(DATA["name"])
+    scene.frame_start = DATA["startFrame"]
+    scene.frame_end = DATA["endFrame"]
+    fps = DATA["fpsNumerator"] / DATA["fpsDenominator"]
+    scene.render.fps = max(1, round(fps))
+    scene.render.fps_base = scene.render.fps / fps
+    scene.render.resolution_x, scene.render.resolution_y = map(int, DATA["resolution"])
+    scene.render.resolution_percentage = 100
+    # The tracker assumes square pixels, regardless of the source's interpretation metadata.
+    scene.render.pixel_aspect_x = scene.render.pixel_aspect_y = 1.0
+    scene.render.film_transparent = True
+    scene.render.motion_blur_shutter = max(0.0, min(2.0, DATA["shutter"]))
+    scene.unit_settings.system = 'METRIC'
+    scene.unit_settings.scale_length = 1.0
+    scene["effectcraft_unit_scale"] = DATA["unitScale"]
+    scene["effectcraft_scale_is_arbitrary"] = True
+    scene["effectcraft_shutter_phase_degrees"] = DATA["shutterPhase"]
+
+    collection = bpy.data.collections.new("EffectCraft Tracking")
+    scene.collection.children.link(collection)
+    camera_data = bpy.data.cameras.new("3D Tracker Camera")
+    camera = bpy.data.objects.new("3D Tracker Camera", camera_data)
+    collection.objects.link(camera)
+    scene.camera = camera
+    camera.rotation_mode = 'QUATERNION'
+    camera_data.type = 'PERSP'
+    camera_data.sensor_fit = 'HORIZONTAL'
+    camera_data.sensor_width = DATA["sensorWidth"]
+    camera_data.sensor_height = (DATA["sensorWidth"] * DATA["resolution"][1]
+                                 / DATA["resolution"][0])
+    camera_data.show_background_images = True
+    camera_data.show_limits = True
+    extent = max([DATA["groundSize"], 1.0]
+                 + [math.dist(p["location"], f["location"])
+                    for p in DATA["points"][::max(1, len(DATA["points"]) // 100)]
+                    for f in DATA["frames"][::max(1, len(DATA["frames"]) // 10)]])
+    camera_data.clip_start = max(0.00001, min(0.1, extent / 10000.0))
+    camera_data.clip_end = max(1000.0, extent * 10.0)
+
+    previous = None
+    for sample in DATA["frames"]:
+        frame = sample["frame"]
+        camera.location = sample["location"]
+        # Exported right/up/back vectors are COLUMNS of Blender's local → world basis.
+        quaternion = Matrix(sample["rotation"]).transposed().to_quaternion()
+        if previous is not None and previous.dot(quaternion) < 0:
+            quaternion.negate()
+        camera.rotation_quaternion = quaternion
+        previous = quaternion.copy()
+        camera.keyframe_insert(data_path="location", frame=frame)
+        camera.keyframe_insert(data_path="rotation_quaternion", frame=frame)
+        camera_data.lens = sample["lens"]
+        camera_data.keyframe_insert(data_path="lens", frame=frame)
+        camera_data.dof.use_dof = sample["dof"]
+        camera_data.dof.focus_distance = sample["focus"]
+        camera_data.dof.aperture_fstop = sample["fstop"]
+        camera_data.dof.aperture_blades = sample["blades"]
+        camera_data.dof.aperture_rotation = (sample["irisRotation"] + math.pi) % math.tau - math.pi
+        camera_data.dof.aperture_ratio = sample["irisRatio"]
+        for prop in ("use_dof", "focus_distance", "aperture_fstop", "aperture_blades",
+                     "aperture_rotation", "aperture_ratio"):
+            camera_data.keyframe_insert(data_path="dof." + prop, frame=frame)
+
+    path = _media_path()
+    if path is not None:
+        try:
+            image = bpy.data.images.load(path, check_existing=False)
+            image.source = DATA["media"]["kind"]
+            background = camera_data.background_images.new()
+            background.source = 'IMAGE'
+            background.image = image
+            background.alpha = 1.0
+            background.display_depth = 'BACK'
+            background.frame_method = 'STRETCH'
+            user = background.image_user
+            user.use_auto_refresh = True
+            user.use_cyclic = False
+            user.frame_start = DATA["startFrame"]
+            user.frame_duration = max(1, min(1048574, image.frame_duration))
+            if image.source == 'MOVIE':
+                for sample in DATA["frames"]:
+                    # Blender uses 1-based image frames; sourceFrame is 0-based.
+                    user.frame_offset = sample["sourceFrame"] - (sample["frame"] - user.frame_start)
+                    camera_data.keyframe_insert(
+                        data_path="background_images[0].image_user.frame_offset",
+                        frame=sample["frame"])
+        except (RuntimeError, ValueError, OSError) as error:
+            DATA["warnings"].append("Blender could not load the background video: " + str(error))
+    else:
+        DATA["warnings"].append("Video not found: " + DATA["media"]["path"]
+                                + ". Place it beside this script or relink the camera background.")
+
+    if DATA["points"]:
+        mesh = bpy.data.meshes.new("Solved Track Points")
+        mesh.from_pydata([p["location"] for p in DATA["points"]], [], [])
+        mesh.update()
+        cloud = bpy.data.objects.new("Solved Track Points", mesh)
+        collection.objects.link(cloud)
+        cloud.show_in_front = True
+        cloud.hide_render = True
+        for name, kind, key in (("track_id", 'INT', "id"), ("reprojection_error", 'FLOAT', "error"),
+                                ("first_frame", 'INT', "first"), ("last_frame", 'INT', "last")):
+            attr = mesh.attributes.new(name=name, type=kind, domain='POINT')
+            for dest, point in zip(attr.data, DATA["points"]):
+                # Track IDs are u32 in EffectCraft; keep the full IDs in the JSON text too.
+                dest.value = point[key] if kind == 'FLOAT' else min(2147483647, point[key])
+
+    if DATA["ground"]:
+        size = DATA["groundSize"]
+        mesh = bpy.data.meshes.new("Solved Ground Plane")
+        mesh.from_pydata([(-size, -size, 0), (size, -size, 0),
+                          (size, size, 0), (-size, size, 0)], [], [(0, 1, 2, 3)])
+        mesh.update()
+        ground = bpy.data.objects.new("Solved Ground Plane", mesh)
+        collection.objects.link(ground)
+        ground.display_type = 'WIRE'
+        ground.hide_render = True
+    for marker in DATA["markers"]:
+        scene.timeline_markers.new(marker["name"], frame=marker["frame"])
+
+    _interpolation(camera)
+    _interpolation(camera_data)
+    metadata = bpy.data.texts.new("EffectCraft Tracking Metadata.json")
+    metadata.write(json.dumps(DATA, ensure_ascii=False, indent=2))
+    scene["effectcraft_metadata_text"] = metadata.name
+    camera_data["effectcraft_average_error_pixels"] = DATA["solve"]["averageError"]
+    camera_data["effectcraft_solve_method"] = DATA["solve"]["methodUsed"]
+    camera_data["effectcraft_focus_source"] = "See warnings in " + metadata.name
+    distortion = DATA["solve"].get("distortion")
+    if distortion:
+        for key in ("k1", "k2", "radius"):
+            camera_data["effectcraft_distortion_" + key] = distortion[key]
+    if bpy.context.window is not None:
+        bpy.context.window.scene = scene
+        for area in bpy.context.window.screen.areas:
+            if area.type == 'VIEW_3D':
+                area.spaces.active.region_3d.view_perspective = 'CAMERA'
+    scene.frame_set(scene.frame_start)
+    for warning in DATA["warnings"]:
+        print("EffectCraft: " + warning)
+    print("EffectCraft: imported", len(DATA["frames"]), "baked camera frames into", scene.name)
+    return scene
+
+
+if __name__ == "__main__":
+    EFFECTCRAFT_SCENE = import_scene()

crates/engine/src/cmd/camera_cmds.rs

@@ -42,11 +42,25 @@ pub fn specs() -> Vec<CommandSpec> {
             create_from_solve
         ),
         cmd!("camera.create", "Create Camera", [], None, "{layer?, effect?}", has_comp, |s, p| create_from_solve(s, &with_kind(p, "camera"))),
+        cmd!(
+            "camera.exportBlender",
+            "Export Scene to Blender...",
+            [],
+            None,
+            "{path: .py, comp?, layer?, effect?, sensorWidth?: mm (default 36), unitScale?: Blender units per comp pixel (default 0.01), startFrame?: positive integer (default 1), includePoints?: true}",
+            has_comp,
+            export_blender
+        ),
         cmd!("camera.setGroundPlane", "Set Ground Plane and Origin", [], None, "{points?: [id] (default: selected), layer?, effect?}", has_comp, set_ground),
         cmd!("camera.deletePoints", "Delete Selected Points", [], None, "{points?: [id] (default: selected), layer?, effect?, wait?}", has_comp, delete_points),
     ]
 }
 
+fn export_blender(s: &mut Session, p: &Value) -> Result<Value> {
+    let (cid, lid, uid) = ct_p(s, p, "camera.exportBlender")?;
+    super::blender::export(s, p, cid, lid, uid)
+}
+
 fn with_kind(p: &Value, kind: &str) -> Value {
     let mut q = p.clone();
     if !q.is_object() {

crates/engine/src/tests.rs

@@ -1,5 +1,6 @@
 mod anim_presets;
 mod anim_tools;
+mod blender;
 mod camera_track;
 mod codec_options;
 mod color_view;

crates/engine/src/tests/blender.rs

@@ -0,0 +1,261 @@
+//! Synthetic camera interchange: projection, timing, DOF and hostile inputs. Optional public
+//! Blender-API oracle: EFFECTCRAFT_BLENDER=/path/to/blender cargo test -p effectcraft-engine tests::blender -- --nocapture.
+
+use effectcraft_effects::camera_tracker as ct;
+use effectcraft_keyframe::Value as KV;
+use effectcraft_project::{Footage, FootageKind, ItemKind, LayerId, LayerSource, build};
+use effectcraft_time::{FrameRate, Tick};
+use effectcraft_track::camtrack::{CameraSolve, Distortion, Ground, ShotType, SolveMethod, SolvedFrame, SolvedPoint};
+use serde_json::{Value, json};
+
+use crate::Session;
+
+fn path(name: &str) -> String {
+    let dir = std::env::temp_dir().join(format!("effectcraft-blender-tests-{}", std::process::id()));
+    std::fs::create_dir_all(&dir).unwrap();
+    dir.join(name).to_string_lossy().into_owned()
+}
+
+fn fixture(ground: bool) -> (Session, LayerId, u64) {
+    let mut s = Session::default();
+    s.execute("comp.new", json!({"name": "Shot '\\ — câmera", "width": 640, "height": 360, "duration": 6})).unwrap();
+    let cid = s.active_comp_id().unwrap();
+    let rate = FrameRate::new(30000, 1001);
+    let lid = s
+        .edit("fixture", None, |p, _| {
+            p.comp_mut(cid).unwrap().frame_rate = rate;
+            let item = p.add_item(
+                "Plate",
+                Default::default(),
+                None,
+                ItemKind::Footage(Footage {
+                    path: std::env::var("EFFECTCRAFT_BLENDER_PLATE").unwrap_or_else(|_| path("plate '\\ — vídeo.mp4")),
+                    width: 640,
+                    height: 360,
+                    frame_rate: FrameRate::FPS_30,
+                    duration: Tick::from_seconds_f64(6.0),
+                    kind: FootageKind::Video,
+                    has_video: true,
+                    ..Default::default()
+                }),
+            );
+            let comp = p.comp(cid).unwrap().clone();
+            let mut layer = build::layer(p, &comp, "Tracked Video", LayerSource::Footage { item }, (640, 360), None);
+            layer.in_point = rate.tick_of(60);
+            layer.out_point = rate.tick_of(63);
+            layer.start_time = rate.tick_of(30);
+            layer.stretch = 200.0;
+            let id = layer.id;
+            p.comp_mut(cid).unwrap().layers.push(layer);
+            Ok(id)
+        })
+        .unwrap();
+    let uid = s.execute("effect.apply", json!({"effect": ct::ID, "layers": [lid.0]})).unwrap()["effects"][0].as_u64().unwrap();
+    let solve = CameraSolve {
+        version: 1,
+        size: [640.0, 360.0],
+        start: rate.tick_of(30).seconds() / 2.0,
+        frame_duration: rate.frame_duration().seconds() / 2.0,
+        shot: ShotType::VariableZoom,
+        method_used: SolveMethod::Typical,
+        average_error: 0.12,
+        frames: (0..3)
+            .map(|i| SolvedFrame {
+                rot: [0.02 * i as f64, -0.03 * i as f64, 0.01 * i as f64],
+                center: [0.1 * i as f64, -0.01 * i as f64, 0.02 * i as f64],
+                focal: 600.0 + i as f64 * 25.0,
+                solved: true,
+            })
+            .collect(),
+        points: vec![
+            SolvedPoint { id: 7, pos: [0.1, 0.2, 2.0], error: 0.13, first: 0, last: 2 },
+            SolvedPoint { id: 9, pos: [-0.3, -0.1, 1.2], error: 0.11, first: 0, last: 1 },
+        ],
+        ground: ground.then_some(Ground { origin: [0.1, 0.2, 2.0], normal: [0.0, -1.0, 0.0], x_axis: [1.0, 0.0, 0.0] }),
+        distortion: ground.then_some(Distortion { k1: 0.01, k2: -0.002, radius: 320.0_f64.hypot(180.0) }),
+    };
+    // Directly install a deterministic solve; no analysis or decoder is needed by these tests.
+    s.execute("prop.set", json!({"layer": lid.0, "path": "effects/#1/solve", "value": solve.to_json()})).unwrap();
+    s.camera_pending.clear();
+    s.execute("layer.select", json!({"layers": [lid.0]})).unwrap();
+    (s, lid, uid)
+}
+
+fn data(script: &str) -> Value {
+    let line = script.lines().find_map(|l| l.strip_prefix("DATA = json.loads(")).unwrap().strip_suffix(')').unwrap();
+    let encoded: String = serde_json::from_str(line).unwrap();
+    serde_json::from_str(&encoded).unwrap()
+}
+
+#[test]
+fn blender_export_bakes_projection_focus_and_retimed_background() {
+    let (mut s, lid, uid) = fixture(true);
+    let result = s.execute("camera.create", json!({"layer": lid.0, "effect": uid})).unwrap();
+    let camera = result["camera"].as_u64().unwrap();
+    s.execute("layer.cameraSettings", json!({"layer": camera, "focusDistance": 800.0, "dof": true, "fStop": 4.0, "lockToZoom": false})).unwrap();
+    for (frame, value) in [(60, 800.0), (62, 1000.0)] {
+        let time = FrameRate::new(30000, 1001).tick_of(frame).seconds();
+        s.execute("prop.addKey", json!({"layer": camera, "path": "cameraOptions/focusDistance", "time": time, "value": value})).unwrap();
+    }
+    let camera_layer = s.active_comp().unwrap().layer(LayerId(camera)).unwrap();
+    assert!(camera_layer.props.prop("cameraOptions/dof").unwrap().value.as_bool());
+    let output = path("oracle-scene.py");
+    let before = s.project.to_json();
+    let r = s.execute_checked("camera.exportBlender", json!({"layer": lid.0, "effect": uid, "path": output, "startFrame": 101})).unwrap();
+    assert_eq!(s.project.to_json(), before, "export must not edit the document");
+    assert_eq!(r["frames"], 3);
+    assert_eq!(r["points"], 2);
+    let script = std::fs::read_to_string(&output).unwrap();
+    let d = data(&script);
+    assert_eq!(d["resolution"], json!([640.0, 360.0]));
+    assert_eq!(d["fpsNumerator"], 30000);
+    assert_eq!(d["fpsDenominator"], 1001);
+    assert_eq!(d["frames"][0]["sourceFrame"], 15, "trim + 200% stretch, not scene frame 101");
+    assert_eq!(d["frames"][2]["sourceFrame"], 16);
+    assert_eq!(d["frames"][0]["focus"], 8.0);
+    assert_eq!(d["frames"][2]["focus"], 10.0);
+    assert_eq!(d["frames"][0]["dof"], true);
+    assert!((d["frames"][0]["fstop"].as_f64().unwrap() - 4.0).abs() < 1e-6);
+    assert_eq!(d["frames"][0]["lens"], 33.75);
+    assert_eq!(d["frames"][2]["lens"], 36.5625);
+    assert_eq!(d["ground"], true);
+    assert_eq!(d["solve"]["distortion"]["k1"], 0.01);
+    assert_eq!(d["points"][0]["location"][2], 0.0, "ground point lies on Blender XY plane");
+
+    // Execute the actual exported artifact in a separately installed Blender, when requested.
+    if let Ok(blender) = std::env::var("EFFECTCRAFT_BLENDER") {
+        let oracle = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("tests/blender_scene_oracle.py");
+        let output = std::process::Command::new(blender)
+            .args(["--background", "--factory-startup", "--python-exit-code", "1", "--python"])
+            .arg(oracle)
+            .arg("--")
+            .arg(&output)
+            .output()
+            .unwrap();
+        assert!(output.status.success(), "Blender oracle failed:\n{}\n{}", String::from_utf8_lossy(&output.stdout), String::from_utf8_lossy(&output.stderr));
+        assert!(String::from_utf8_lossy(&output.stdout).contains("EFFECTCRAFT_BLENDER_ORACLE_OK"));
+    }
+}
+
+#[test]
+fn blender_export_bakes_reverse_time_remap_and_footage_loops() {
+    let (mut s, lid, _) = fixture(false);
+    let cid = s.active_comp_id().unwrap();
+    let rate = FrameRate::new(30000, 1001);
+    s.edit("retimed fixture", None, |p, _| {
+        let layer = p.comp(cid).unwrap().layer(lid).unwrap();
+        let item = layer.source.item().unwrap();
+        let keys = [(60, 8.0), (61, 6.0), (62, -1.0)]
+            .map(|(frame, time)| effectcraft_keyframe::Keyframe::new(layer.layer_time(rate.tick_of(frame)), KV::Scalar(time)));
+        let mut remap = build::Ids(&mut p.next_id).prop("timeRemap", "Time Remap", KV::Scalar(8.0));
+        remap.keys = keys.to_vec();
+        p.comp_mut(cid).unwrap().layer_mut(lid).unwrap().props.children.push(remap.into());
+        if let ItemKind::Footage(f) = &mut p.item_mut(item).unwrap().kind {
+            f.loop_count = 2;
+        }
+        Ok(())
+    })
+    .unwrap();
+    let output = path("remap.py");
+    s.execute_checked("camera.exportBlender", json!({"layer": lid.0, "path": output})).unwrap();
+    let d = data(&std::fs::read_to_string(output).unwrap());
+    let indices: Vec<i64> = d["frames"].as_array().unwrap().iter().map(|f| f["sourceFrame"].as_i64().unwrap()).collect();
+    assert_eq!(indices, vec![60, 0, 0], "reverse remap wraps the 6-second video and clamps negative source time, as the media pool does");
+}
+
+#[test]
+fn blender_export_defaults_and_script_escaping() {
+    let (mut s, lid, _) = fixture(false);
+    let output = path("escaped.py");
+    let r = s
+        .execute_checked("camera.exportBlender", json!({"layer": lid.0, "path": output, "includePoints": false, "sensorWidth": 24.0, "unitScale": 0.1}))
+        .unwrap();
+    assert_eq!(r["points"], 0);
+    let script = std::fs::read_to_string(&output).unwrap();
+    let d = data(&script);
+    assert!(d["name"].as_str().unwrap().contains("'\\ — câmera"));
+    assert_eq!(d["frames"][0]["lens"], 22.5);
+    assert_eq!(d["frames"][0]["dof"], false);
+    assert!(r["warnings"].as_array().unwrap().iter().any(|w| w.as_str().unwrap().contains("cannot be recovered")));
+    match std::process::Command::new("python3").args(["-c", "import ast,sys; ast.parse(open(sys.argv[1], encoding='utf-8').read())", &output]).status() {
+        Ok(status) => assert!(status.success(), "generated script must parse even with quoted/Unicode paths"),
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => eprintln!("Python AST oracle skipped: python3 is not installed"),
+        Err(e) => panic!("Python AST oracle failed: {e}"),
+    }
+}
+
+#[test]
+fn blender_export_rejects_invalid_arguments_and_write_failures() {
+    let (mut s, lid, _) = fixture(false);
+    for params in [
+        json!({"sensorWidth": 0}),
+        json!({"sensorWidth": "wide"}),
+        json!({"unitScale": -1}),
+        json!({"startFrame": -1}),
+        json!({"startFrame": 1.5}),
+        json!({"startFrame": 1048574}),
+        json!({"includePoints": "yes"}),
+        json!({"bogus": true}),
+        json!({"path": path("bad.blend")}),
+    ] {
+        let mut p = json!({"layer": lid.0, "path": path("invalid.py")});
+        p.as_object_mut().unwrap().extend(params.as_object().unwrap().clone());
+        assert!(s.execute_checked("camera.exportBlender", p.clone()).is_err(), "must reject {p}");
+    }
+    let blocker = path("blocker");
+    std::fs::write(&blocker, b"not a directory").unwrap();
+    let p = format!("{blocker}/scene.py");
+    assert!(s.execute_checked("camera.exportBlender", json!({"layer": lid.0, "path": p})).unwrap_err().to_string().contains("cannot write"));
+}
+
+#[test]
+fn blender_export_rejects_malformed_solves_without_panicking() {
+    for variant in ["empty", "unsolved", "zero-focal", "bad-ground", "huge-resolution", "mismatched-range"] {
+        let (mut s, lid, uid) = fixture(false);
+        let cid = s.active_comp_id().unwrap();
+        let mut solve = ct::solve(&crate::camera_track::static_params(s.active_comp().unwrap().layer(lid).unwrap().props.find_group(uid).unwrap()))
+            .unwrap()
+            .as_ref()
+            .clone();
+        match variant {
+            "empty" => solve.frames.clear(),
+            "unsolved" => solve.frames[0].solved = false,
+            "zero-focal" => solve.frames[0].focal = 0.0,
+            "bad-ground" => solve.ground = Some(Ground::default()),
+            "huge-resolution" => solve.size[0] = 1e10,
+            _ => {
+                solve.frames.pop();
+            }
+        }
+        s.edit("corrupt solve", None, |p, _| {
+            p.comp_mut(cid).unwrap().layer_mut(lid).unwrap().props.find_group_mut(uid).unwrap().prop_mut(ct::SOLVE).unwrap().value = KV::Str(solve.to_json());
+            Ok(())
+        })
+        .unwrap();
+        s.camera_pending.clear();
+        let result = s.execute_checked("camera.exportBlender", json!({"layer": lid.0, "path": path("corrupt.py")}));
+        assert!(result.is_err(), "must reject {variant}");
+    }
+}
+
+#[test]
+fn blender_export_respects_script_write_permission() {
+    let (mut s, lid, _) = fixture(false);
+    let output = path("script-permissions.py");
+    let params = json!({"layer": lid.0, "path": output});
+    for (from_script, allowed) in [(true, false), (true, true), (false, false), (false, true)] {
+        std::fs::write(&output, b"existing file").unwrap();
+        s.prefs.scripting.allow_scripts_write_files = allowed;
+        let result =
+            if from_script { s.execute_for_script("camera.exportBlender", params.clone()) } else { s.execute_checked("camera.exportBlender", params.clone()) };
+        assert!(!s.running_for_script(), "script origin must be restored after success or error");
+        let contents = std::fs::read_to_string(&output).unwrap();
+        if from_script && !allowed {
+            assert!(result.unwrap_err().to_string().contains("Allow Scripts to Write Files"));
+            assert_eq!(contents, "existing file", "blocked scripts must not replace an existing file");
+        } else {
+            assert_eq!(result.unwrap()["frames"], 3);
+            assert!(contents.contains("def import_scene():"));
+        }
+    }
+}

crates/engine/tests/blender_scene_oracle.py

@@ -0,0 +1,61 @@
+"""Public-API oracle for scripts generated by src/tests/blender.rs; no Blender source dependency."""
+import json
+import math
+import runpy
+import sys
+
+import bpy
+from bpy_extras.object_utils import world_to_camera_view
+from mathutils import Quaternion, Vector
+
+path = sys.argv[sys.argv.index("--") + 1]
+before = set(bpy.data.scenes)
+exported = runpy.run_path(path, run_name="__main__")
+scene = exported["EFFECTCRAFT_SCENE"]
+data = exported["DATA"]
+assert before.issubset(set(bpy.data.scenes)), "existing scenes were removed"
+assert scene not in before
+assert scene.frame_start == 101 and scene.frame_end == 103
+assert abs(scene.render.fps / scene.render.fps_base - 30000 / 1001) < 1e-4
+assert (scene.render.resolution_x, scene.render.resolution_y) == (640, 360)
+camera = scene.camera
+assert camera.animation_data.action is not None
+assert camera.data.animation_data.action is not None
+assert camera.data.sensor_fit == 'HORIZONTAL'
+metadata = json.loads(bpy.data.texts[scene["effectcraft_metadata_text"]].as_string())
+assert metadata["solve"]["averageError"] == 0.12
+cloud = scene.objects["Solved Track Points"]
+assert len(cloud.data.vertices) == 2
+assert cloud.hide_render
+assert cloud.data.attributes["track_id"].data[0].value == 7
+assert any(obj.name.startswith("Solved Ground Plane") for obj in scene.objects)
+
+for i, sample in enumerate(data["frames"]):
+    scene.frame_set(sample["frame"])
+    bpy.context.view_layer.update()
+    assert abs(camera.data.lens - sample["lens"]) < 1e-5
+    assert abs(camera.data.dof.focus_distance - sample["focus"]) < 1e-5
+    assert abs(camera.data.dof.aperture_fstop - sample["fstop"]) < 1e-5
+    assert camera.data.dof.use_dof
+    assert (camera.location - Vector(sample["location"])).length < 1e-5
+    raw = data["solve"]["frames"][i]
+    rot = Vector(raw["rot"])
+    rotation = Quaternion(rot.normalized(), rot.length).to_matrix() if rot.length else Quaternion().to_matrix()
+    for vertex, point in zip(cloud.data.vertices, data["solve"]["points"]):
+        relative = rotation @ (Vector(point["pos"]) - Vector(raw["center"]))
+        expected = (raw["focal"] * relative.x / relative.z + 320,
+                    raw["focal"] * relative.y / relative.z + 180)
+        projected = world_to_camera_view(scene, camera, vertex.co)
+        actual = (projected.x * 640, (1.0 - projected.y) * 360)
+        assert math.dist(actual, expected) < 0.002, (sample["frame"], actual, expected)
+
+    if "Video not found" not in " ".join(data["warnings"]):
+        background = camera.data.background_images[0]
+        assert background.image.source == 'MOVIE'
+        assert tuple(background.image.size) == (640, 360)
+        user = background.image_user
+        actual_source = sample["frame"] - user.frame_start + user.frame_offset
+        assert actual_source == sample["sourceFrame"], (actual_source, sample["sourceFrame"])
+        assert user.use_auto_refresh
+
+print("EFFECTCRAFT_BLENDER_ORACLE_OK")

crates/ui-egui/src/i18n/ui.rs

@@ -2996,6 +2996,7 @@ const UKRAINIAN: &[(&str, &str)] = &[
 
 // Brazilian Portuguese.
 const PORTUGUESE: &[(&str, &str)] = &[
+    ("Export Scene to Blender...", "Exportar cena para o Blender..."),
     ("   OK   ", "   OK   "),
     ("  Delete  ", "  Excluir  "),
     (" Open Auto-Save ", " Abrir salvamento automático "),

crates/ui-egui/src/menus/frontend.rs

@@ -560,6 +560,7 @@ pub(super) fn file_dialog(app: &mut EffectcraftApp, id: &str, params: &Value) ->
         "anim.applyPreset" => ("path", Ask::Open(&["ecpreset", "json"])),
         "view.exportGuides" => ("path", Ask::Save("Guides.json")),
         "view.importGuides" => ("path", Ask::Open(&["json"])),
+        "camera.exportBlender" => ("path", Ask::Save("Tracked Scene.py")),
         "file.exportLottie" => ("path", Ask::Save("Animation.json")),
         "file.importLottie" => ("path", Ask::Open(&["json", "lottie"])),
         "file.importProject" => ("path", Ask::Open(&["ecproj", "ecprojx"])),

crates/ui-egui/src/panels/camera_tracker_ui.rs

@@ -430,6 +430,11 @@ pub fn editor(
             actions.push(("camera.create".into(), me.clone()));
         }
         app.auto.add(&format!("effectControls.cameraTracker.{}.createCamera", g.uid), b3, "Create Camera");
+        let export = Rect::from_min_size(pos2(r.min.x + 24.0, r.min.y + 70.0), vec2(218.0, 22.0));
+        if widgets::text_button(ui, export, tr("Export Scene to Blender..."), false, &t, egui::Id::unique(("ct-blender", g.uid))).clicked() && !busy {
+            actions.push(("camera.exportBlender".into(), me.clone()));
+        }
+        app.auto.add(&format!("effectControls.cameraTracker.{}.exportBlender", g.uid), export, "Export Scene to Blender...");
     }
     let status = match app.session.camera_progress() {
         Some(pr) if running => pr.banner(),
@@ -457,4 +462,4 @@ pub fn editor(
 }
 
 /// Height of [`editor`].
-pub const EDITOR_HEIGHT: f32 = 68.0;
+pub const EDITOR_HEIGHT: f32 = 100.0;

crates/ui-egui/tests/it/ui_camera_tracker.rs

@@ -16,8 +16,9 @@ const H: f64 = 360.0;
 
 fn app() -> (EffectcraftApp, u64, u64) {
     let mut s = Session::default();
-    s.execute("comp.new", json!({"name": "Shot", "width": W, "height": H, "duration": 2})).unwrap();
-    let plate = s.execute("layer.newSolid", json!({"name": "Plate", "color": "#406080"})).unwrap()["layer"].as_u64().unwrap();
+    s.execute("comp.new", json!({"name": "Shot", "width": W as u32, "height": H as u32, "duration": 2, "frameRate": 30})).unwrap();
+    let plate =
+        s.execute("layer.newSolid", json!({"name": "Plate", "color": "#406080", "width": W as u32, "height": H as u32})).unwrap()["layer"].as_u64().unwrap();
     let r = s.execute("effect.apply", json!({"effect": ct::ID, "layers": [plate]})).unwrap();
     let uid = r["effects"][0].as_u64().unwrap();
     // A synthetic solve: a static camera (focal 600) looking at a 6 × 4 grid of points on z = 1.
@@ -135,7 +136,11 @@ fn viewer_points_selection_and_effect_controls() {
     h.state_mut().show_panel(PanelKind::EffectControls);
     h.run_steps(4);
     let all = ids(&h);
-    for want in [format!("effectControls.cameraTracker.{uid}.analyze"), format!("effectControls.cameraTracker.{uid}.createCamera")] {
+    for want in [
+        format!("effectControls.cameraTracker.{uid}.analyze"),
+        format!("effectControls.cameraTracker.{uid}.createCamera"),
+        format!("effectControls.cameraTracker.{uid}.exportBlender"),
+    ] {
         assert!(all.contains(&want), "missing {want}");
     }
     // Tracker panel: Track Camera is available for the selected layer.
@@ -145,6 +150,56 @@ fn viewer_points_selection_and_effect_controls() {
     assert!(h.state().session.is_enabled("track.camera"));
 }
 
+#[test]
+fn blender_export_button_opens_python_dialog_and_writes_scene() {
+    use effectcraft_engine::project::{Footage, FootageKind, ItemKind, LayerId, LayerSource};
+    let (mut a, plate, uid) = app();
+    let cid = a.session.active_comp_id().unwrap();
+    a.session
+        .edit("video fixture", None, |p, _| {
+            let item = p.add_item(
+                "Video",
+                Default::default(),
+                None,
+                ItemKind::Footage(Footage {
+                    path: "/tmp/effectcraft-ui-synthetic.mp4".into(),
+                    kind: FootageKind::Video,
+                    width: W as u32,
+                    height: H as u32,
+                    has_video: true,
+                    duration: effectcraft_engine::time::Tick::from_seconds_f64(2.0),
+                    ..Default::default()
+                }),
+            );
+            p.comp_mut(cid).unwrap().layer_mut(LayerId(plate)).unwrap().source = LayerSource::Footage { item };
+            Ok(())
+        })
+        .unwrap();
+    a.session.camera_pending.clear();
+    let output = std::env::temp_dir().join(format!("effectcraft-ui-blender-{}.py", std::process::id()));
+    let selected_path = output.clone();
+    a.hooks.pick_save_file = Some(Box::new(move |name, ext| {
+        assert!(name.ends_with(".py"));
+        assert_eq!(ext, "py");
+        Some(selected_path.to_string_lossy().into_owned())
+    }));
+    let shot = std::env::var("EFFECTCRAFT_BLENDER_UI_SNAPSHOT").ok();
+    let builder = Harness::builder().with_size(egui::vec2(1600.0, 1000.0));
+    let builder = if shot.is_some() { builder.wgpu() } else { builder };
+    let mut h = builder.build_eframe(|_| a);
+    h.state_mut().show_panel(PanelKind::EffectControls);
+    h.run_steps(5);
+    let button = rect(&h, &format!("effectControls.cameraTracker.{uid}.exportBlender"));
+    if let Some(path) = shot {
+        h.render().expect("render export button").save(path).unwrap();
+    }
+    click(&mut h, button.center(), Default::default());
+    assert!(output.exists(), "UI export failed: {}", h.state().ui.status);
+    let script = std::fs::read_to_string(output).expect("clicking the export button saves a Python scene");
+    assert!(script.contains("def import_scene():"));
+    assert_eq!(h.state().session.active_comp().unwrap().layers.len(), 1, "export does not create a camera in the source project");
+}
+
 /// Drag with `button` from `from` to `to` in steps, then release.
 fn drag_with(h: &mut Harness<'_, EffectcraftApp>, button: egui::PointerButton, from: egui::Pos2, to: egui::Pos2) {
     h.input_mut().events.push(egui::Event::PointerMoved(from));

docs/agents.md

@@ -446,7 +446,12 @@ and Origin), `camera.createFromSolve {kind: text|solid|null|shadowCatcher, point
 {center, normal, size?}, multiple?}` (Create Text / Solid / Null / Shadow Catcher, Camera and Light,
 Create Multiple …), `camera.deletePoints {points?, wait?}` (re-solves; with Auto-delete Points
 Across Time the same feature's other tracks go too) and `camera.create` (the Create Camera button).
-Each is one undo step; the first create adds the one-node "3D Tracker Camera" keyed on every frame.
+Each edit is one undo step; the first create adds the one-node "3D Tracker Camera" keyed on every frame.
+
+`camera.exportBlender {path: ".py", layer?, effect?, sensorWidth?: 36, unitScale?: 0.01,
+startFrame?: 1, includePoints?: true}` exports the solve as an executable Blender scene script:
+baked camera/lens/focus, synced video background, points and ground. See
+[Blender camera export](blender-camera-export.md) for framing, assumptions and limitations.
 Changing the layer's frames clears the analysis; changing `effects/#1/shotType`,
 `effects/#1/horizontalAngleOfView`, `effects/#1/advanced/solveMethod` re-solves the stored tracks.
 

docs/blender-camera-export.md

@@ -0,0 +1,101 @@
+# Exporting a tracked camera to Blender
+
+After the **3D Camera Tracker** finishes solving, click **Export Scene to Blender...** in its
+Effect Controls and save the `.py` file. In Blender 4.0 or newer, open it in the Scripting
+workspace's Text Editor and choose **Run Script**. The script creates and activates a new scene;
+it preserves existing scenes and objects. Save the resulting `.blend` normally.
+
+The script uses Blender's public Python API, with no add-on or Python dependencies beyond
+Blender itself. For unattended use: `blender --background --python "Tracked Scene.py"`.
+That imports the scene in memory; it does not automatically save a `.blend`.
+
+## Transferred data
+
+- Camera position and quaternion rotation baked on every analyzed frame, with consistent
+  quaternion signs and linear interpolation; zoom/lens animation, including Variable Zoom.
+- Tracking input/video resolution, horizontal sensor fit, exact rational composition FPS,
+  frame range and composition markers within the analyzed interval. The first analyzed frame
+  becomes Blender frame 1 by default; the original composition timestamps remain in metadata.
+- The original video or still as the camera's background image, at full opacity, refreshed on
+  frame changes. Source-frame offsets are baked too, accounting for trim, stretch, source FPS
+  and Time Remap. This is a viewport background, not a render/compositor background.
+- Focus distance, DOF switch, f-stop, iris blade count, rotation and aspect sampled from the
+  tracker's linked **3D Tracker Camera**, including keyframes and expressions. Create that
+  camera and adjust its Camera Options before exporting to transfer custom focus settings.
+- Solved 3D points as a non-rendering vertex mesh, with point attributes for track ID,
+  reprojection error and first/last visible frame. A chosen ground plane becomes Blender's XY
+  plane, with its origin preserved and a non-rendering wire plane as a placement guide.
+- Shutter duration (not automatically enabled), plus the original shutter phase in metadata.
+- A Blender Text datablock named `EffectCraft Tracking Metadata.json` containing the complete
+  solve, optional original 2D tracks, per-frame timings, source interpretation, diagnostics and
+  export warnings. Radial distortion coefficients are also camera custom properties.
+
+Coordinates are converted from EffectCraft's right/down/forward world to Blender's
+right/forward/up world, including the camera's local up and negative-Z viewing direction.
+Export uses the tracking input's framing, not the footage layer's final 2D placement in the
+composition. Camera pose and lens always come from the solve; subsequent manual pose/lens edits
+on the linked camera are not substituted for the tracked motion.
+
+## What cannot be inferred
+
+Monocular tracking cannot recover absolute scene scale, physical sensor size, optical focus,
+f-stop or exposure from feature tracks. The default sensor width is an assumption of **36 mm**;
+the focal length in millimeters is derived from it while preserving the solved field of view.
+The default scale is **0.01 Blender units per composition-world pixel**, not a measurement.
+Without a linked camera, DOF is disabled and focus distance uses the default solved scene depth.
+Blender's physical DOF approximates EffectCraft's blur model: Blur Level and Iris Roundness are
+retained in metadata, but have no direct Blender equivalent.
+
+Brown-model radial `k1`/`k2` coefficients use radius normalized to half the image diagonal.
+They are preserved, **not** assigned to Blender's different lens-distortion model. For a precise
+match when distortion is nonzero, use an undistorted plate; the script prints a warning.
+The tracker assumes square pixels, so Blender renders square pixels; any non-square source
+interpretation is retained in metadata and flagged.
+
+The `.py` references the video; it does not contain a copy of the video's bytes. When moving it,
+keep the video next to the script (same filename), or relink the background image in Blender.
+Missing/unsupported media produces a warning while retaining the imported camera and geometry.
+Masks and effects applied before the tracker are not baked into the original media. Export
+requires a direct video/still footage layer at the analyzed size; render precomps, sequences or
+size-changing preprocessing to a video and track that video first.
+
+## Agent / control-channel command
+
+```json
+{
+  "command": "camera.exportBlender",
+  "params": {
+    "layer": "#1",
+    "path": "/output/Tracked Scene.py",
+    "sensorWidth": 36,
+    "unitScale": 0.01,
+    "startFrame": 1,
+    "includePoints": true
+  }
+}
+```
+
+`comp`, `layer` and `effect` select the tracker as with `camera.analyze`. Without explicit
+selection, the selected tracker (or first tracker in the composition) is used. `sensorWidth`,
+`unitScale`, `startFrame` and `includePoints` are optional. The reply contains file size,
+exported frame/point counts and warnings. Writing uses the host's atomic file service.
+Calls issued by scripts require **Allow Scripts to Write Files and Access Network** in
+Settings ▸ Scripting & Expressions. Export from the UI or control channel remains available
+with that preference off.
+
+Export is limited to 100,000 analyzed frames, 100,000 points and 64 MiB of serialized scene data;
+invalid, stale or incomplete solves return an actionable error without modifying the document.
+
+## Verification
+
+Engine tests check argument validation, escaped/Unicode paths, fractional FPS, trim/stretch,
+focus/f-stop, zoom, ground placement, malformed solves and write failures. To additionally run
+the generated artifact against an installed Blender's public API:
+
+```sh
+EFFECTCRAFT_BLENDER=/path/to/blender cargo test -p effectcraft-engine tests::blender -- --nocapture
+```
+
+Optionally set `EFFECTCRAFT_BLENDER_PLATE` to a local synthetic 640×360 video to exercise media
+loading and source-frame offsets. The oracle checks every synthetic point's projection through
+the imported camera on every frame, as well as animation, DOF, timing and scene preservation.