# Physics Placement Evaluation

Date: 2026-07-12

![Three selected props settled on the committed placement floor](physics-placement-settled.png)

The native Wayland editor is shown with the committed
`assets/levels/physics_placement_showcase.scn.ron` fixture. Placement Prop A, B, and C were
multi-selected and released from three different heights through the hand/down-arrow action in the
existing horizontal viewport toolbar.

## Acceptance

- All three props used the hydrated Avian cuboid colliders and settled on Placement Floor after
  1.5 simulated seconds.
- During preview the HUD reported selection count, simulated time, and Settled state; transform
  gizmos and viewport picking did not compete with the modal tool.
- Escape restored every starting transform and left history empty.
- A second run committed with Enter as exactly one `Undo: Move Selection` entry.
- Ctrl+Z restored all three elevated starting transforms; Ctrl+Y restored the settled transforms.
- Opening the fixture immediately after the terrain showcase no longer panicked on a stale
  generated terrain-material binding; the scene-switch regression is covered in
  `blacksite_surface`.
- The runtime log contained no physics-placement, scene-load, render-pipeline, or GPU validation
  error after the stale-binding fix.

Packaged-runtime tests remain intentionally deferred by project-owner request.