Mesh Faces are out of order when Transparency is on

[WowieMan]

Godot version

3.3.2

System information

MacOS 11.3.1, M1, GLES3

Issue description

When the “transparent” flag is turned on in a material and “Cull Mode” is disabled, the meshes faces are out of order.

Steps to reproduce

Create a mesh and a material, add a texture and set the “Transparent” flag to true, also you will need to set “Cull Mode” to disable.

Minimal reproduction project

BugReport.zip

[Calinou]

This is expected due to the limitationd of transparency sorting. As a workaround, use alpha scissor (alpha testing) instead of alpha blending.

#50721 will most likely not fix this because sorting is done on a per-mesh basis, not a per-face basis (which would be too expensive).

[WowieMan]

When I turn the “transparent“ flag off and turn on alpha scissors, something really odd happens. Is this normal?

[Calinou]

If the depth draw mode is set to Opaque Prepass, this could be due to #36669.

[WowieMan]

Yep, I have Opaque Pre-Pass is turned on and #36669 looks exactly like what is happening here.

[WowieMan]

One of the work around in #36669 did work, but sadly the cube’s faces are still out of order.

[Calinou]

One of the work around in #36669 did work, but sadly the cube’s faces are still out of order.

To prevent this starting in 3.4beta, you can render each face with its own MeshInstance using a PlaneMesh or QuadMesh resource. This relies on #50721, so it won't work in 3.3.2.

[WowieMan]

Oh okay, where can I download the beta, Or do I have to compile it from source?

[Calinou]

Oh okay, where can I download the beta, Or do I have to compile it from source?

You have to compile the 3.x branch from source, as there are no beta releases yet.

[WowieMan]

Okay thanks, I’ll go test that.

[Calinou]

@WowieMan Did you manage to get it working in 3.4 beta6?

[WowieMan]

No, not really. I was able to get  around it by creating two meshes, one for the shadow and one for the  visuals, though that's probably not the best solution long-term.