1 files changed, 37 insertions, 0 deletions
diff --git a/source/blender/draw/engines/eevee/shaders/effect_downsample_frag.glsl b/source/blender/draw/engines/eevee/shaders/effect_downsample_frag.glsl
new file mode 100644
index 00000000000..156be108a14
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/effect_downsample_frag.glsl
@@ -0,0 +1,37 @@
+/**
+ * Simple downsample shader. Takes the average of the 4 texels of lower mip.
+ **/
+
+uniform sampler2D source;
+uniform float fireflyFactor;
+
+out vec4 FragColor;
+
+float brightness(vec3 c)
+{
+	return max(max(c.r, c.g), c.b);
+}
+
+void main()
+{
+#if 0
+	/* Reconstructing Target uvs like this avoid missing pixels if NPO2 */
+	vec2 uvs = gl_FragCoord.xy * 2.0 / vec2(textureSize(source, 0));
+
+	FragColor = textureLod(source, uvs, 0.0);
+#else
+	vec2 texel_size = 1.0 / vec2(textureSize(source, 0));
+	vec2 uvs = gl_FragCoord.xy * 2.0 * texel_size;
+	vec4 ofs = texel_size.xyxy * vec4(0.75, 0.75, -0.75, -0.75);
+
+	FragColor  = textureLod(source, uvs + ofs.xy, 0.0);
+	FragColor += textureLod(source, uvs + ofs.xw, 0.0);
+	FragColor += textureLod(source, uvs + ofs.zy, 0.0);
+	FragColor += textureLod(source, uvs + ofs.zw, 0.0);
+	FragColor *= 0.25;
+
+	/* Clamped brightness. */
+	float luma = max(1e-8, brightness(FragColor.rgb));
+	FragColor *= 1.0 - max(0.0, luma - fireflyFactor) / luma;
+#endif
+}
+\ No newline at end of file