The root of this issue is that FLocalVertexFactory is doing manual vertex fetch in the shader. In HLSL, this relies on SV_VertexId. In GLSL, it's gl_VertexId. HLSL does not include the base vertex index and SV_VertexId always starts at zero. GLSL, on the other hand, does include the base vertex index.
As a result, this works correctly in OpenGL / Vulkan, and incorrectly on DirectX.
Run attached project and notice the four triangles in the upper left corner. All four triangles should have unique vertex colors; instead, the second column of triangles mirrors the first. This is because the second column of triangles is using a BaseVertexIndex != 0.[Link Removed]
How does TextureRenderTarget2D get TArray<uint8> type data?
Why does the REMOVE method of map container remove elements have memory leaks?
How to delete some elements correctly when deleting an array loop?
UMG RichText not appear image when packaged
What is the cause of the packaging error falling back to 'GameUserSettings' in ue5?
What is the difference between Camera and CineCamera?
What controls of umg have mouse wheel events in UE4.27?
How to assign a value to a member of UMG's UMaterialInterface pointer type in C++?
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-74848 in the post.
| 0 |
| Component | UE - Rendering Architecture - RHI |
|---|---|
| Affects Versions | 4.22 |
| Target Fix | 4.23 |
| Created | May 20, 2019 |
|---|---|
| Resolved | May 21, 2019 |
| Updated | Jul 30, 2019 |