Vulkan: SoftBody3D is incorrectly culled due to its visibility AABB not being updated

[jcostello]

Godot version

v4.0.dev.custom_build [88b347d]

System information

Ubuntu 21.04. RTX 2060

Issue description

This issue is very strange but like the title says. If the softbody plane mesh start above the camera, it is complete invisible even if the soft body is in direction with the camera view.

Steps to reproduce

Use the InvisibleCloth.tscn scene from the Minimal reproduction project

Minimal reproduction project

Godot 4.0 SoftBody.zip

[Calinou]

This happens because the visibility AABB isn't automatically adjust to account for the displayed vertices. I'm not sure if it's possible to do this in a cheap way.

In the meantime, increase the Extra Cull Margin property on the mesh by a few units so that the frustum/occlusion culling is done in a more forgiving way. Don't make this value too large or the mesh won't be culled when it could be.

[jcostello]

Good to know that. Since this is not related to soft bodies then the issue can be closed or rename to explain the cause

[pouleyKetchoupp]

This happens because the visibility AABB isn't automatically adjust to account for the displayed vertices. I'm not sure if it's possible to do this in a cheap way.

Soft bodies are supposed to update their AABB after calculating the new vertex positions, but there's probably a bug either in godot physics or in the vulkan renderer.

godot/scene/3d/soft_dynamic_body_3d.cpp

Line 90 in 30cf49e

RS::get_singleton()->mesh_set_custom_aabb(mesh, p_aabb);

@jcostello Do you know if it happens also in 3.x or just in 4.0?

[jcostello]

@pouleyKetchoupp 4.0

[James103]

Can confirm using the originally linked project in Godot 4.0 alpha 1.

[James103]

Still occurs in Godot 4.0 alpha 4 with the originally linked project.
Workaround: Move the SoftBody so that it is in view of the Camera or increase Extra Cull Margin.