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# System prepended metadata

title: '# GLTF Extensions Group 2023-12-07 - KHR_physics extension'

---

# GLTF Extensions Group 2023-12-07 - KHR_physics extension

## Static body representation

OMI wants to have a static body versus standalone collision shapes. Unity is an outlier with this behaviour. 

KHR suggests to not have bodies for static objects. For objects that start out static and can become dynamic later, KHR suggests using kinematic.

> Normal to have thousands of collision shapes. Please prove us wrong that this is expensive

> Shared callbacks for split physics shapes. / How areas are defined?

Converting 10,000 static bodies to kinematics causes performance problems.

Trimesh are usually permitted only for static bodies.

## Trigger object grouping

OMI prefers to have a way to group triggers for scripting engines. Would be a huge headache.

Godot has an area node which represent triggers.

Can't make an event that can be attached to multiple trigger shapes.

House with a cube body and a triangle cube. How do we avoid trigging multiple events going through the areas.

## Tapered capsules / cones

OMI prefers simpler types, but can emulate these shapes as convex hull so it's not essential.

Tapered cylinder - OMI believes this is a bad idea. Like cylinders - by that logic.

It can be emulated with convex hull.

Size of implementation effort could be a problem.

### Example of features of gltf2 features not used

Like texture coordinates rotations

## References

https://github.com/eoineoineoin/glTF_Physics/issues/4

