Vulkan: Depth prepass does not respect cull mode

[GiantBlargg]

Godot version

4.0.dev (c1320aa)

System information

Arch Linux, Vulkan, AMD RX 5500 XT (mesa 21.1.3)

Issue description

The depth pre pass always seems to render with backface culling, instead of the culling mode set by the shader. This is visually obvious with frontface culling, but it probably has performance impacts for disabled culling as well.

Expected (3.3.2):

Steps to reproduce

Create an opaque material with Cull Mode set to "Front"

Minimal reproduction project

Culling.zip

[Calinou]

@GiantBlargg Can you reproduce this in 3.3.2?

[GiantBlargg]

@Calinou No. This issue is not present in 3.3.2

[GiantBlargg]

The cause seems to be that the shadow material is used for depth pre-pass. In many cases the shadow material is set to the default material which is backface culled.

godot/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp

Lines 2467 to 2481 in 5c3055e

	SceneShaderForwardClustered::MaterialData *material_shadow = nullptr;
	void *surface_shadow = nullptr;
	if (!p_material->shader_data->uses_particle_trails && !p_material->shader_data->writes_modelview_or_projection && !p_material->shader_data->uses_vertex && !p_material->shader_data->uses_discard && !p_material->shader_data->uses_depth_pre_pass) {
	flags |= GeometryInstanceSurfaceDataCache::FLAG_USES_SHARED_SHADOW_MATERIAL;
	material_shadow = (SceneShaderForwardClustered::MaterialData *)storage->material_get_data(scene_shader.default_material, RendererStorageRD::SHADER_TYPE_3D);
	RID shadow_mesh = storage->mesh_get_shadow_mesh(p_mesh);
	if (shadow_mesh.is_valid()) {
	surface_shadow = storage->mesh_get_surface(shadow_mesh, p_surface);
	}
	} else {
	material_shadow = p_material;
	}

godot/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp

Line 2498 in 5c3055e

sdcache->shader_shadow = material_shadow->shader_data;

godot/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp

Lines 342 to 345 in 5c3055e

	if (shadow_pass || p_params->pass_mode == PASS_MODE_DEPTH) { //regular depth pass can use these too
	material_uniform_set = surf->material_uniform_set_shadow;
	shader = surf->shader_shadow;
	mesh_surface = surf->surface_shadow;