at_midBlock.w is always 0 on 1.8.0 betas

[ASaull]

What happened?

at_midBlock.w seems to always return 0 even though the BLOCK_EMISSION_ATTRIBUTE feature flag is still set.

This is used by Bliss Shaders to add the light from light blocks when using Flood Fill, and no longer works as of the 1.8.0 beta builds.

Light blocks do work in Photon shaders, however, since Photon uses the vanilla lightmap to add the light from light blocks.

Screenshots

1.8.0 Beta 4 (and I also tested Beta 1, same issue)

1.7.3

Log output

No response

Minecraft Version

1.21.1

Iris Version

1.8.0-beta.4+1.21-fabric.jar

Operating System

Windows 11

What is your GPU?

RTX 3070

Additional context

This is the relevant section of Bliss Shader code.

	voxelId = uint(mc_Entity.x + 0.5);

	#ifdef IRIS_FEATURE_BLOCK_EMISSION_ATTRIBUTE
		if (voxelId == 0u && at_midBlock.w > 0) voxelId = uint(BLOCK_LIGHT_1 + at_midBlock.w - 1);
	#endif

	if (voxelId == 0u) voxelId = 1u;

	originPos += at_midBlock.xyz/64.0;

at_midblock.xyz works as expected, but at_midblock.w is always 0.