Physics Interpolation Breaks Terrain

[mrjustaguy]

Terrain3D version

v0.9.2

System information

4.4 dev1

Is the issue reproducable in the demo?

Not applicable

Issue description

Turning on Physics Interpolation Breaks the Terrain at runtime while moving, causing 2 issues:

1. Textures smear
2. Clipmaps get detached causing holes

They happen because the position is getting Interpolated. Disabling Interpolation on Terrain3D in question doesn't do anything.

This May be an Issue with how Godot is Handling it's Interpolation, or something internally setup wrong on Terrain3D's end regarding how the Meshes are handled, but I'm not sure Which is the case.

If the Clipmaps are using MultiMesh see godotengine/godot#91818 (comment) to resolve this issue

Logs

No response

[TokisanGames]

4.4 is not supported until the release candidates. Clipmaps don't use multimesh, but foliage does.

Does the issue occur with our collision disabled?

Does the issue still exist with Jolt?

Disabling Interpolation on Terrain3D in question doesn't do anything.

We don't have a way to enable or disable interpolation

Did you report this on Godot's issues, or on the PR that implements physics interpolation, or on their developer chat? Physics Interpolation is the new thing here, not Terrain3D. The temporal nature of the meshes may conflict with the interpolation, similar to how TAA and FSR have issues. #302

[mrjustaguy]

Physics interpolation has no effect on the physics engine used, as it's basically just getting last physics frame transform and current physics frame transform and the process time to figure out what the display transform should be for the given frame.

To this end, Disabling Collisions and Jolt result in absolutely no differences.

It's hard to tell if this is a Terrain3D or a Godot issue, given that Physics Interpolation fundamentally does require proper user usage to work right.

[TokisanGames]

"Physics" Interpolation is a confusing name then. If it's not a Godot bug, then at the very least we need documentation on how to use it or setup our meshes or shader to support it, or disable it, or not conflict with it. The key feature of our clipmap terrain is that the vertices and meshes move potentially every frame, though visually they look the same. That causes TAA & FSR to get wonky and is probably the same here.