Niagara Multiple Ribbon Wrong Triangle

Development Rendering
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1

When I used Niagara’s RibbonRenderer to render multiple Ribbons by controlling the RibbonID, I found that when the particles disappeared, the last isolated particle left in the previous Ribbon would automatically connect to the beginning of the next Ribbon, making two overlapping weird triangles for a few frames.

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By the way，when the previous Ribbon has only 2 particles, the UV was wrong.

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These problems only occur during GPU simulation. I have checked the compute shaders but cannot figured out. Is it a bug? Some garbage information are reused?

2

重现步骤
Open the project and check the “RibbonIDTest” folder. Open the level and play.

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3

Hello,

This was fixed in CL 36152918, although I’m not sure how easy that will be to integrate into 5.4.

I would also suggest integrating CL 44042760 as that fixes a separate issue with GPU ribbons.

Thanks,

Stu

4

Hey, it looks like that isn’t fixed when I tested locally.

Will take a look into that.

Thanks,

Stu

5

The fix turned out to be quite easy for this inside NiagaraRibbonRibbonUVParamCalculation.usf line 233 the comparison against 1 was incorrect it should be 0.

I’ll submit a fix for this one passed code review.

Thanks,

Stu

6

I submitted the fix in CL 44686747 UE5 Main.

Thanks,

Stu

7

Thank you, Stu

8

Hello Stu, is the UV problem also fixed?

9

Thank you, Stu