1. Create an arena for the mjData instance used by the passive viewer visualization.
When using the passive viewer, stuff gets copied from the real mjData into a minimal struct.
That struct didn't have a stack, and now visualization for Flex does stack allocs.
2. Add missing a missing field in scene state for flex visualization.
3. Fix a memory leak where mjvScene wasn't released on exit in the passive viewer.
4. Add some locks in places where the render thread and Simulate::Sync collide.
This fixes#1280.
PiperOrigin-RevId: 591891676
Change-Id: I592f286cab9719c8d9af84e42f9756ea1f9f1971
This change also requires user scripts to explicitly synchronize changes to physics state to the viewer. The Simulate class was reconfigured so that certain UI events are handled during this sync operation, outside of the render loop on the main thread. These correspond to operations that require access to the full mjModel/mjData.
To support other, more interactive operations (e.g. camera movements), a new mjvSceneState struct is introduced which captures only the portion of the physics state required for scene re-rendering. The mjvSceneState is updated from mjModel/mjData during the viewer sync operation, and is significantly cheaper than a full mj_copyModel and mj_copyData.
Fixes https://github.com/deepmind/mujoco/issues/796
PiperOrigin-RevId: 525723636
Change-Id: Id08d0210a2c067d5afe85e2bf104f276aeddd75e
Nimrod Gileadi