// MinecraftPT — RTWSM Building Warp
// Builds the final warp curve (cumulative importance) from the importance map.

#include "/Lib/Settings.glsl"
#include "/Lib/Utilities.glsl"

const ivec3 workGroups = ivec3(32, 1, 1);
layout (local_size_x = 32) in;

layout (rg16) uniform writeonly image2D img_rtwWarp1D;

uniform sampler2D rtwImportance2D;

void main(){
	int y = int(gl_GlobalInvocationID.y);

	// Compute the cumulative importance curve for this row
	float total = 0.0;
	for (int x = 0; x < RTW_RESOLUTION; x++){
		total += textureLod(rtwImportance2D, vec2(float(x) / float(RTW_RESOLUTION), float(y) / float(RTW_RESOLUTION_Y)), 0.0).r;
	}

	// Write warp curve: row 0 = cumulative, row 1 = inverse
	if (total > 0.0){
		float cum = 0.0;
		for (int x = 0; x < RTW_RESOLUTION; x++){
			cum += textureLod(rtwImportance2D, vec2(float(x) / float(RTW_RESOLUTION), float(y) / float(RTW_RESOLUTION_Y)), 0.0).r;
			imageStore(img_rtwWarp1D, ivec2(x, 0), vec4(cum / total, 0.0, 0.0, 0.0));
		}

		// Inverse: for each output position find input position
		for (int x = 0; x < RTW_RESOLUTION; x++){
			float target = float(x) / float(RTW_RESOLUTION - 1);
			int lo = 0;
			int hi = RTW_RESOLUTION - 1;
			for (int i = 0; i < 10; i++){
				int mid = (lo + hi) / 2;
				float v = textureLod(rtwImportance2D, vec2(float(mid) / float(RTW_RESOLUTION), float(y) / float(RTW_RESOLUTION_Y)), 0.0).r;
				if (v < target) lo = mid; else hi = mid;
			}
			float inv = float(lo) / float(RTW_RESOLUTION);
			imageStore(img_rtwWarp1D, ivec2(x, 1), vec4(inv, 0.0, 0.0, 0.0));
		}
	}else{
		// Identity warp
		for (int x = 0; x < RTW_RESOLUTION; x++){
			float v = float(x) / float(RTW_RESOLUTION);
			imageStore(img_rtwWarp1D, ivec2(x, 0), vec4(v, 0.0, 0.0, 0.0));
			imageStore(img_rtwWarp1D, ivec2(x, 1), vec4(v, 0.0, 0.0, 0.0));
		}
	}
}