#version 430

uniform float roll;

uniform writeonly image2D destTex;

layout (local_size_x = 16, local_size_y = 16) in;

void main() {
	ivec2 storePos = ivec2(gl_GlobalInvocationID.xy);

	float localCoef = length(vec2(ivec2(gl_LocalInvocationID.xy)-8)/8.0);

	float globalRCoef = sin(float(gl_WorkGroupID.x+gl_WorkGroupID.y)*0.1 + roll)*0.5;
	float globalGCoef = sin(float(gl_WorkGroupID.x+gl_WorkGroupID.y)*0.05 + roll)*0.5;
	float globalBCoef = sin(float(gl_WorkGroupID.x+gl_WorkGroupID.y)*0.2 + roll)*0.5;

	float r = 0.5 - globalRCoef * localCoef;
	float g = 0.5 - globalGCoef * localCoef;
	float b = 0.5 - globalBCoef * localCoef;

	imageStore(destTex, storePos, vec4(r, g, b, 1.0));
}