Bloom (#12791)

Adds configurable light exposure control and bloom effect (light bleeding) with client-side settings.

client/shaders/extract_bloom/opengl_fragment.glsl

@@ -0,0 +1,21 @@
+#define rendered texture0
+
+uniform sampler2D rendered;
+uniform mediump float exposureFactor = 2.5;
+uniform float bloomLuminanceThreshold = 1.0;
+
+#ifdef GL_ES
+varying mediump vec2 varTexCoord;
+#else
+centroid varying vec2 varTexCoord;
+#endif
+
+
+void main(void)
+{
+	vec2 uv = varTexCoord.st;
+	vec4 color = texture2D(rendered, uv).rgba;
+	// translate to linear colorspace (approximate)
+	color.rgb = pow(color.rgb, vec3(2.2)) * exposureFactor;
+	gl_FragColor = vec4(color.rgb, 1.0); // force full alpha to avoid holes in the image.
+}