User feedback: the self-drawn scale handles clash visually with the
ImGuizmo translate/rotate rods (different size/style, clearly not one
widget). Keep the library widget for all three ops for visual
consistency and prevent mis-drags by masking degenerate axes via
SetAxisMask:
- translate: axis ~ parallel to camera-to-object line (sin < 0.25)
- scale: axis ~ perpendicular to camera-to-object line (|dot| < 0.1,
intersection numerator identically zero -> grab fails/values jump)
OR axis ~ parallel to view direction (|dot| > 0.98, zero screen
displacement -> value never changes)
- rotate: screen-space math, no degeneracy, no mask
Masked axes are neither drawn nor activatable; a slight view change
restores them. Center uniform-scale square (MT_SCALE_XYZ, pure screen
space) stays available in any view.
ImGuizmo scale hover/drag relies on ray-plane intersection with the
axis as plane normal; in front views (axis ⟂ camera-to-object) the
intersection numerator is identically zero, so handles can't be
grabbed and values jump randomly; axes parallel to the view have zero
screen displacement. Submodule is read-only and AxisMask can only hide
degenerate axes, not replace them.
Replace the library scale path entirely with a screen-space gizmo:
- three axis rods (line + end square) + center uniform-scale square,
constant screen size in any view
- axis drag: mouse delta projected onto the axis' screen direction
- axis pointing at camera: radial mapping (drag away = grow)
- center square: uniform scale (library MT_SCALE_XYZ semantics)
- Ctrl snapping quantizes the result; scale clamped >= 0.01
- pick suppressed while hovering/dragging the self-drawn handles
atdunbg