1 files changed, 65 insertions, 0 deletions
diff --git a/shaders/combine.frag b/shaders/combine.frag
new file mode 100644
index 0000000..4240528
--- /dev/null
+++ b/shaders/combine.frag
@@ -0,0 +1,65 @@
+#version 450
+
+#define LIST_END ~0x0
+#define SORT_MAX 32
+
+layout (location = 0) out vec4 color;
+
+layout(binding = 0) uniform mvp {
+	mat4 model;
+	mat4 view;
+	mat4 proj;
+	uint count;
+} ubo;
+
+layout(binding = 1) buffer fragment_buffer {
+	uvec3 fragments[];
+};
+layout(binding = 2, r32ui) uniform uimage2D head;
+layout(binding = 3) buffer counter {
+	int data;
+};
+
+vec4 blend_colors(uint packed_color, vec4 dst_color) {
+	const vec4 src_color = unpackUnorm4x8(packed_color);
+	return vec4(mix(dst_color.rgb, src_color.rgb, src_color.a), dst_color.a * (1.0f - src_color.a));
+}
+
+void main() {
+	color = vec4(0, 0, 0, 1);
+	uint idx = imageLoad(head, ivec2(gl_FragCoord.xy)).r;
+	imageStore(head, ivec2(gl_FragCoord.xy), ivec4(LIST_END, 0, 0, 0));
+
+	uvec2 sorted[SORT_MAX];
+	uint sorted_count = 0;
+
+	// TODO: use a proper struct
+	while (idx != LIST_END) {
+		const uvec3 fragment = fragments[idx];
+		idx = fragment.x;
+
+		if (sorted_count < SORT_MAX) {
+			uint i = sorted_count;
+			for(; i > 0 && fragment.z > sorted[i - 1].y; i--) {
+				sorted[i] = sorted[i - 1];
+			}
+			sorted[i] = fragment.yz;
+			sorted_count++;
+		} else if (fragment.z > sorted[0].y) {
+			color = blend_colors(sorted[0].x, color);
+			uint i = 0;
+			for (; i < SORT_MAX - 1 && fragment.z < sorted[i + 1].y; i++) {
+				sorted[i] = sorted[i + 1];
+			}
+			sorted[i] = fragment.yz;
+		} else {
+			color = blend_colors(fragment.y, color);
+		}
+	}
+
+	for (int i = 0; i < sorted_count; i++) {
+		color = blend_colors(sorted[i].x, color);
+	}
+
+	color.a = 1.0f - color.a;
+}