Merge pull request #2118 from ChristopherLinnett/fix/issue-2092-camera-focus-crash

fix: bound Classic 3D depth-of-field blur and reject non-finite focus distances (#2092)

crates/render/src/three_d/compose.rs

@@ -18,7 +18,7 @@ use std::sync::Arc;
 use effectcraft_color::{BlendMode, blend_pixel};
 use effectcraft_effects::Buf;
 use effectcraft_geom::{Mat3, Mat4, Vec3, vec3};
-use effectcraft_project::{Layer, LightKind, MatteKind};
+use effectcraft_project::{Layer, LightKind, MatteKind, limits};
 use effectcraft_raster::{Image, Px, hash_noise};
 use effectcraft_time::Tick;
 use rayon::prelude::*;
@@ -287,12 +287,45 @@ fn prepare_with<'a>(r: &Renderer, ctx: &EvalCtx<'_>, layer: &'a Layer, order: us
 }
 
 /// Blur radius (buffer pixels) of every buffer pixel of a plane at `world` (layer → world), from
-/// its camera depth: the circle of confusion over the on-screen size of one layer pixel there.
-fn dof_radii(cam: &CameraState, dof: &super::camera::Dof, world: Mat4, buf: &Buf) -> Vec<f32> {
-    dof_radii_at(cam, dof, world, (buf.img.width as usize, buf.img.height as usize), buf.offset, buf.scale)
+/// its camera depth: the circle of confusion over the on-screen size of one layer pixel there, at
+/// most `cap` ([`dof_radius_cap`]).
+fn dof_radii(cam: &CameraState, dof: &super::camera::Dof, world: Mat4, buf: &Buf, cap: f64) -> Vec<f32> {
+    dof_radii_at(cam, dof, world, (buf.img.width as usize, buf.img.height as usize), buf.offset, buf.scale, cap)
 }
 
-fn dof_radii_at(cam: &CameraState, dof: &super::camera::Dof, world: Mat4, (w, h): (usize, usize), offset: [f64; 2], scale: f64) -> Vec<f32> {
+/// Pixels a padded blur buffer may have: the ~16 million layer buffers are held to
+/// ([`crate::Renderer::raster_scale`]), or twice the buffer when that is larger, so a big buffer
+/// can still be blurred. The blur holds a few images of this size at once whatever its level
+/// count ([`super::bokeh::progressive_blur`]), so blurring a small plane costs no more memory than
+/// blurring a large layer.
+const DOF_PAD_BUDGET: f64 = 16.0e6;
+
+/// Comp pixels per buffer pixel below which a plane isn't blurred. Such a plane covers almost no
+/// screen area (a 0%-scaled layer, one at an extreme distance), while its radius in buffer
+/// pixels grows without bound as it shrinks: blurring it would cost the most for the least.
+const DOF_MIN_SCREEN_SCALE: f64 = 1e-3;
+
+/// The largest blur radius (buffer pixels) of a `w`×`h` buffer: the one whose padded copy just
+/// fits [`DOF_PAD_BUDGET`]. The circle of confusion has no bound of its own (a focus distance far
+/// beyond the scene, a near-zero layer scale), so memory sets the limit; ordinary bokeh stays far
+/// below it and is never clamped.
+pub(super) fn dof_radius_cap(dof: &super::camera::Dof, w: u32, h: u32) -> f64 {
+    let (w, h) = (w as f64, h as f64);
+    let budget = DOF_PAD_BUDGET.max(2.0 * w * h);
+    // (w + 2p)·(h + 2p) = budget, solved for the padding p.
+    let pad = (((w - h) * (w - h) + 4.0 * budget).sqrt() - (w + h)) / 4.0;
+    ((pad - 2.0) / iris_stretch(dof)).max(0.0)
+}
+
+pub(super) fn dof_radii_at(
+    cam: &CameraState,
+    dof: &super::camera::Dof,
+    world: Mat4,
+    (w, h): (usize, usize),
+    offset: [f64; 2],
+    scale: f64,
+    cap: f64,
+) -> Vec<f32> {
     let s = scale.max(1e-9);
     let sx = world.apply_vec(vec3(1.0, 0.0, 0.0)).length().max(1e-9);
     let at = |x: f64, y: f64| cam.depth(world.apply(vec3((x - offset[0]) / s, (y - offset[1]) / s, 0.0)));
@@ -306,31 +339,48 @@ fn dof_radii_at(cam: &CameraState, dof: &super::camera::Dof, world: Mat4, (w, h)
             if z <= super::camera::NEAR {
                 continue;
             }
-            // coc · ½ / (zoom / z · sx) · scale
-            *o = (dof.coc(z) * 0.5 * z / (cam.zoom * sx) * s) as f32;
+            // coc · ½ / (zoom / z · sx) · scale. Infinity clamps to the cap like any large radius,
+            // so the blur keeps growing with defocus; only NaN, which has no defocus, stays sharp.
+            let r = dof.coc(z) * 0.5 * z / (cam.zoom * sx) * s;
+            *o = if r.is_nan() || cam.zoom * sx / (z * s) < DOF_MIN_SCREEN_SCALE { 0.0 } else { r.min(cap) as f32 };
         }
     });
     out
 }
 
+/// How much the iris' aspect ratio stretches a blur radius along its longer axis.
+fn iris_stretch(dof: &super::camera::Dof) -> f64 {
+    let a = dof.iris.aspect.clamp(0.01, 100.0).sqrt();
+    a.max(1.0 / a)
+}
+
 /// The padding [`dof_blur`] gives a buffer whose largest blur radius is `rmax`.
 fn dof_pad(dof: &super::camera::Dof, rmax: f64) -> u32 {
-    let a = dof.iris.aspect.clamp(0.01, 100.0).sqrt().max(1.0 / dof.iris.aspect.clamp(0.01, 100.0).sqrt());
-    (rmax * a).ceil() as u32 + 2
+    ((rmax * iris_stretch(dof)).ceil() as u32).saturating_add(2)
+}
+
+/// The size of `img` padded by `pad` on every side, or `None` past [`limits::MAX_SIZE`] on a side:
+/// [`DOF_PAD_BUDGET`] bounds the area, so a long thin buffer could still outgrow a side.
+fn padded_size(img: &Image, pad: u32) -> Option<(u32, u32)> {
+    let grow = |n: u32| n.saturating_add(pad.saturating_mul(2));
+    let (w, h) = (grow(img.width), grow(img.height));
+    (w <= limits::MAX_SIZE && h <= limits::MAX_SIZE).then_some((w, h))
 }
 
 /// [`dof_blur`] planned for an accelerator: the padding, radius map and levels, and the padded
 /// buffer's layer-space bounds. `None` when nothing blurs.
 fn dof_plan(cam: &CameraState, dof: &super::camera::Dof, world: Mat4, buf: &Buf) -> Option<(PlaneDof, [f64; 4])> {
-    let radii = dof_radii(cam, dof, world, buf);
+    let cap = dof_radius_cap(dof, buf.img.width, buf.img.height);
+    let radii = dof_radii(cam, dof, world, buf, cap);
     let rmax = radii.iter().copied().fold(0.0f32, f32::max) as f64;
     if rmax <= 0.3 {
         return None;
     }
     let pad = dof_pad(dof, rmax);
-    let (w, h) = (buf.img.width as usize + 2 * pad as usize, buf.img.height as usize + 2 * pad as usize);
+    let (wp, hp) = padded_size(&buf.img, pad)?;
+    let (w, h) = (wp as usize, hp as usize);
     let offset = [buf.offset[0] + pad as f64, buf.offset[1] + pad as f64];
-    let radius = dof_radii_at(cam, dof, world, (w, h), offset, buf.scale);
+    let radius = dof_radii_at(cam, dof, world, (w, h), offset, buf.scale, cap);
     let levels = super::bokeh::blur_levels(&radius)?;
     let s = buf.scale.max(1e-9);
     let bounds = [-offset[0] / s, -offset[1] / s, (w as f64 - offset[0]) / s, (h as f64 - offset[1]) / s];
@@ -339,16 +389,20 @@ fn dof_plan(cam: &CameraState, dof: &super::camera::Dof, world: Mat4, buf: &Buf)
 
 /// Depth of field for one plane: highlights boosted, then a bokeh-shaped blur by depth.
 fn dof_blur(cam: &CameraState, dof: &super::camera::Dof, world: Mat4, buf: Arc<Buf>) -> Arc<Buf> {
-    let radii = dof_radii(cam, dof, world, &buf);
+    let cap = dof_radius_cap(dof, buf.img.width, buf.img.height);
+    let radii = dof_radii(cam, dof, world, &buf, cap);
     let rmax = radii.iter().copied().fold(0.0f32, f32::max) as f64;
     if rmax <= 0.3 {
         return buf;
     }
     let pad = dof_pad(dof, rmax);
+    if padded_size(&buf.img, pad).is_none() {
+        return buf;
+    }
     let mut padded = buf.img.padded(pad);
     super::bokeh::boost_highlights(&mut padded, &dof.highlight);
     let pbuf = Buf { img: padded, offset: [buf.offset[0] + pad as f64, buf.offset[1] + pad as f64], scale: buf.scale };
-    let pr = dof_radii(cam, dof, world, &pbuf);
+    let pr = dof_radii(cam, dof, world, &pbuf, cap);
     // The (cached, shared) layer buffer stays untouched; the blurred copy is per frame.
     Arc::new(Buf { img: super::bokeh::progressive_blur(&pbuf.img, &dof.iris, &pr), offset: pbuf.offset, scale: pbuf.scale })
 }