Real-time physics

[pmudry]

Rigid bodies first

1. Falling spheres/cubes, collisions, stacking, bouncing.
   Easy to understand visually, low engineering risk.
   Best “wow per day of work”.

2. Cheap deformation tricks
   Squash/stretch on impact (scale object briefly based on collision impulse).
   Wobble shader (procedural displacement for jelly-like look).

3. Morph targets between 2-3 meshes for “soft-ish” behavior.
   Looks dynamic without expensive FEM/MPM.

4. GPU-friendly particle/cloth-lite
   Small cloth patch with position-based dynamics (PBD), low vertex count.
   Or particle fountain/smoke impostors lit by your path tracer.
   Keep counts low and cap update cost.

Best Hybrid Strategy

1. Simulate at fixed low rate (30-60 Hz) with capped budget.
2. Render progressively as usual.
3. Update only a few dynamic objects each frame.
4. Freeze physics when camera is moving fast, resume when idle.

Great Demo Feature Set

Physics Sandbox Mode

Press F to drop objects into scene.
Press R reset.

Material picker: rubber/metal/glass.

Impact Deformation Mode
On collision, spheres flatten then recover in 200-400 ms.
Show toggle “Deformation ON/OFF”.

Interactive Trigger

Click to apply impulse (“poke” objects).
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