What happened?

The texture of water flow blocks are not staying connected if a shader has waving animation for water.

Screenshots

I feel like videos show the problem better.

This is Optifine + Sildurs Vibrant Shaders v1.28 High
https://streamable.com/h9xpfp

This is Iris + Sildurs Vibrant Shaders v1.28 High
https://streamable.com/sa9hv0

Relevant log output

NA

Iris and Minecraft Version

iris-mc1.16.5-1.1.0 for 1.16.5

Are you running Sodium along with Iris?

Yes

Operating System

Windows 10

What is your GPU?

GTX 1050

Java Version

Java 16.0.1

Additional context

No response

Applying the following diff to gbuffers_water.vsh causes the issue to go away:

 	#ifdef Waving_Water
-		float fy = fract(worldpos.y + 0.001);
+		float fy = fract(worldpos.y + 0.01);

Seems like Sodium's fluid rendering might be breaking expectations of Sildur's Vibrant Shaders.

I can confirm that this issue still occurs as of Minecraft 1.19 + Iris 1.2.5 on Sildur's Vibrant 1.32, and that @coderbot16's workaround for the rounding precision error still works (with no real noticeable side effects for OptiFine, if you're using the same modified shaders for both Iris and OptiFine).

Reproduced on both NVIDIA RTX 2060 (NVGRD 512.95, DCH; Windows 10 19044.1826 21H2) and Apple G13J (macOS 12.4 21F79).