1 files changed, 87 insertions, 0 deletions
diff --git a/servers/rendering/rasterizer_rd/shaders/luminance_reduce.glsl b/servers/rendering/rasterizer_rd/shaders/luminance_reduce.glsl
new file mode 100644
index 0000000000..4bf5b7e7f1
--- /dev/null
+++ b/servers/rendering/rasterizer_rd/shaders/luminance_reduce.glsl
@@ -0,0 +1,87 @@
+/* clang-format off */
+[compute]
+
+#version 450
+
+VERSION_DEFINES
+
+#define BLOCK_SIZE 8
+
+layout(local_size_x = BLOCK_SIZE, local_size_y = BLOCK_SIZE, local_size_z = 1) in;
+/* clang-format on */
+
+shared float tmp_data[BLOCK_SIZE * BLOCK_SIZE];
+
+#ifdef READ_TEXTURE
+
+//use for main texture
+layout(set = 0, binding = 0) uniform sampler2D source_texture;
+
+#else
+
+//use for intermediate textures
+layout(r32f, set = 0, binding = 0) uniform restrict readonly image2D source_luminance;
+
+#endif
+
+layout(r32f, set = 1, binding = 0) uniform restrict writeonly image2D dest_luminance;
+
+#ifdef WRITE_LUMINANCE
+layout(set = 2, binding = 0) uniform sampler2D prev_luminance;
+#endif
+
+layout(push_constant, binding = 1, std430) uniform Params {
+	ivec2 source_size;
+	float max_luminance;
+	float min_luminance;
+	float exposure_adjust;
+	float pad[3];
+}
+params;
+
+void main() {
+
+	uint t = gl_LocalInvocationID.y * BLOCK_SIZE + gl_LocalInvocationID.x;
+	ivec2 pos = ivec2(gl_GlobalInvocationID.xy);
+
+	if (any(lessThan(pos, params.source_size))) {
+
+#ifdef READ_TEXTURE
+		vec3 v = texelFetch(source_texture, pos, 0).rgb;
+		tmp_data[t] = max(v.r, max(v.g, v.b));
+#else
+		tmp_data[t] = imageLoad(source_luminance, pos).r;
+#endif
+	} else {
+		tmp_data[t] = 0.0;
+	}
+
+	groupMemoryBarrier();
+	barrier();
+
+	uint size = (BLOCK_SIZE * BLOCK_SIZE) >> 1;
+
+	do {
+		if (t < size) {
+			tmp_data[t] += tmp_data[t + size];
+		}
+		groupMemoryBarrier();
+		barrier();
+
+		size >>= 1;
+
+	} while (size >= 1);
+
+	if (t == 0) {
+		//compute rect size
+		ivec2 rect_size = min(params.source_size - pos, ivec2(BLOCK_SIZE));
+		float avg = tmp_data[0] / float(rect_size.x * rect_size.y);
+		//float avg = tmp_data[0] / float(BLOCK_SIZE*BLOCK_SIZE);
+		pos /= ivec2(BLOCK_SIZE);
+#ifdef WRITE_LUMINANCE
+		float prev_lum = texelFetch(prev_luminance, ivec2(0, 0), 0).r; //1 pixel previous exposure
+		avg = clamp(prev_lum + (avg - prev_lum) * params.exposure_adjust, params.min_luminance, params.max_luminance);
+#endif
+		imageStore(dest_luminance, pos, vec4(avg));
+	}
+}