FramentShaderWaveCoherency test shader (Vulkan 1.1)

FramentShaderWaveCoherency.txt

#version 450
#extension GL_ARB_separate_shader_objects : enable
#extension GL_KHR_shader_subgroup_basic : enable
#extension GL_KHR_shader_subgroup_ballot : enable
#extension GL_KHR_shader_subgroup_vote : enable
#extension GL_KHR_shader_subgroup_arithmetic : enable

layout(location = 0) out vec4 outColor;

//#define VISUALIZE_WAVES
#define VISUALIZE_COHERENCY

vec3 hash32(vec2 p)
{
	vec3 p3 = fract(vec3(p.xyx) * vec3(.1031, .1030, .0973));
	p3 += dot(p3, p3.yxz+19.19);
	return fract((p3.xxy+p3.yzz)*p3.zyx);
}

void main() 
{
#ifdef VISUALIZE_WAVES
	vec3 fragmentHash = hash32(gl_FragCoord.xy);
	vec3 lane0Hash = subgroupBroadcast(fragmentHash, 0);
	outColor = vec4(lane0Hash, 0.0);
#endif

#ifdef VISUALIZE_COHERENCY
	bool allLanesActive = subgroupBallotBitCount(subgroupBallot(true)) == gl_SubgroupSize;

	uvec2 tileCoord16 = uvec2(gl_FragCoord.xy) / 16;

	int numTilesAffectedLane = 0;
	bool laneProcessed = false;
	while (!laneProcessed)
	{
		uvec2 firstActiveLaneTile = subgroupBroadcastFirst(tileCoord16);	
		bool inSameTileAsFirst = all(equal(tileCoord16, firstActiveLaneTile));

		laneProcessed = laneProcessed || inSameTileAsFirst;
		numTilesAffectedLane++;
	}
	
	int numTilesAffected = subgroupMax(numTilesAffectedLane);

	outColor.r = allLanesActive ? 0.0 : 1.0;
	outColor.g = float(5-numTilesAffected) * (1.0 / 4.0);
	outColor.b = 0;
	outColor.a = 1;
#endif
}