A model space view carries a twist (radians CCW, View.twist, serde default
0). VIEWTWIST reports it read-only. Each VPORTS tile keeps its own twist
(VportTile.twist, DXF VPORT group 51 read and written; a single untiled
Model view's twist is kept as a lone *Active VPORT tile). VIEW Save stores
and Restore applies NamedView::twist. ZOOM fits in the twisted screen frame;
zooms, pans, the 3D mouse and view.set keep it; ZOOM Previous turns it back.
DVIEW starts with "Select objects or <use DVIEWBLOCK>:" (the picked objects,
or the DVIEWBLOCK sample, are the only things drawn while it runs) and
repeats the "Enter option [CAmera/TArget/Distance/POints/PAn/Zoom/
TWist/CLip/Hide/Off/Undo]:" prompt. TWist, PAn, Zoom, Off and Undo work on
2D views; the 3D options say they are not available yet (docs/gaps.md F1).
DVIEW works inside an active layout viewport: the doc Viewport gains a view
twist (DXF VIEWPORT group 51), drawn turned on screen and in plots, mapped
through MSPACE views, snaps and CHSPACE; a twist made there is one undo
step. A layout with no active viewport refuses it, as does view.set's twist.
Canvas: the model view and every VPORTS tile draw turned by their twist.
`Xf` gains `twist`: `to_screen` turns (p - centre) by it before scaling,
`to_world` is its exact inverse, `world_bounds` is the box of the four
turned rect corners. The GPU needs no shader change: `Xf::gpu_xform` builds
the callback xform for the drawing, drag, highlight, viewport and mask
layers. Pans map screen deltas back through the twist; clicks, hover, snaps,
grips and wheel zoom go through `to_world`/`to_screen`. Grid lines and axes
stay world-aligned; the selection window is drawn as the world box it
selects.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Typed VPLAYER ran its JSON form with no parameters and ended, so its
options ran as commands (F started FILLET). It now loops on
?/Color/Freeze/Thaw/Reset/Newfrz/Vpvisdflt until Enter, asks for layer
names (wildcards, comma lists) and then which viewports to change:
All/Select/Current/Except current (Current by default inside a viewport,
Select by point on the sheet in paper space). Changes go through
viewport.set, layer.new and layer.set; the session is one undo step.
The Model tab refuses it.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
