Shader compilation errors in NiagaraSpriteVertexFactory.ush

Development Rendering
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1

Hi,

We have the exact same issue as mentioned in this UDN Post:

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This currently causes issues at cook time with shader compilation errors:

NiagaraSpriteVertexFactory.ush:462:39: error: no member named ‘TexCoord_Unflipped’ in ‘FVertexFactoryIntermediates’

When opening the offending Material in the Editor and do ‘Show HLSL’, we clearly see that:

  • NUM_MATERIAL_TEXCOORDS_VERTEX 4
  • NUM_MATERIAL_TEXCOORDS 1

… and this situation prevents float4 TexCoord_Unflipped from being declared and compiled (see NiagaraSpriteVertexFactory.ush).

It might seem like a simple fix, but the impacts and risk seems quite high.

Wondering what is the plan on Epic’s side regarding fixing this issue?

2

Steps to Reproduce

3

Hi David,

I never manage to make a repro for the original issue, which is what made me reluctant to submit the change.

I did sit with the modification locally for about a month and didn’t encounter any obvious problems with it.

If you have a way to repro the issue that would be great and I could submit this in time for 5.6.

Thanks,

Stu

4

Thanks for the information, when I find time I’ll see if I can use that to get a repro.

5

Hi Stuart,

So far it appears the issue involves Material Layers and Material Blends, with at least 1 Material Layer having multiple Texture Coordinate Channels (4 in our case).

I will try to get a vanilla repro.

Thanks,

David

6

I also encountered this issue, it seemed strangely intermittent and the asset appears to otherwise be rendering correctly instead of using default material. It is a mic (using mat attrib layers) used on a static mesh used by a niagara mesh renderer. Mesh does have 4 UV channels which the mic makes use of.

Can you share the revision of that potential fix you mentioned, we might want to merge it in.

7

That was the key bit of information, managed to make myself a repro doing this.

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Just doing some verification but this gives me more confidence in a fix now!

Thanks,

Stu

8

The change is submitted into UE5 Main CL 42565841, this fixes both Niagara & Cascade CPU+GPU vertex factories.

Thanks,

Stu

9

Hi Stu,

Will integrate this and test, getting back to you next week.

10

I merged in the change and recooked and confirmed that the fail to compiles are gone, thanks.

11

Great, thanks for confirming!