1 files changed, 86 insertions, 0 deletions
diff --git a/src/rend2/glsl/ssao_fp.glsl b/src/rend2/glsl/ssao_fp.glsl
new file mode 100644
index 00000000..6263284c
--- /dev/null
+++ b/src/rend2/glsl/ssao_fp.glsl
@@ -0,0 +1,86 @@
+uniform sampler2D u_ScreenDepthMap;
+
+uniform vec4   u_ViewInfo; // zfar / znear, zfar
+
+varying vec2   var_ScreenTex;
+
+vec2 poissonDisc[9] = vec2[9](
+vec2(-0.7055767, 0.196515),    vec2(0.3524343, -0.7791386),
+vec2(0.2391056, 0.9189604),    vec2(-0.07580382, -0.09224417),
+vec2(0.5784913, -0.002528916), vec2(0.192888, 0.4064181),
+vec2(-0.6335801, -0.5247476),  vec2(-0.5579782, 0.7491854),
+vec2(0.7320465, 0.6317794)
+);
+
+// Input: It uses texture coords as the random number seed.
+// Output: Random number: [0,1), that is between 0.0 and 0.999999... inclusive.
+// Author: Michael Pohoreski
+// Copyright: Copyleft 2012 :-)
+// Source: http://stackoverflow.com/questions/5149544/can-i-generate-a-random-number-inside-a-pixel-shader
+
+float random( const vec2 p )
+{
+  // We need irrationals for pseudo randomness.
+  // Most (all?) known transcendental numbers will (generally) work.
+  const vec2 r = vec2(
+    23.1406926327792690,  // e^pi (Gelfond's constant)
+     2.6651441426902251); // 2^sqrt(2) (Gelfond-Schneider constant)
+  //return fract( cos( mod( 123456789., 1e-7 + 256. * dot(p,r) ) ) );
+  return mod( 123456789., 1e-7 + 256. * dot(p,r) );  
+}
+
+mat2 randomRotation( const vec2 p )
+{
+	float r = random(p);
+	float sinr = sin(r);
+	float cosr = cos(r);
+	return mat2(cosr, sinr, -sinr, cosr);
+}
+
+float getLinearDepth(sampler2D depthMap, const vec2 tex, const float zFarDivZNear)
+{
+		float sampleZDivW = texture2D(depthMap, tex).r;
+		return 1.0 / mix(zFarDivZNear, 1.0, sampleZDivW);
+}
+
+float ambientOcclusion(sampler2D depthMap, const vec2 tex, const float zFarDivZNear, const float zFar)
+{
+	float result = 0;
+
+	float sampleZ = zFar * getLinearDepth(depthMap, tex, zFarDivZNear);
+
+	vec2 expectedSlope = vec2(dFdx(sampleZ), dFdy(sampleZ)) / vec2(dFdx(tex.x), dFdy(tex.y));
+	
+	if (length(expectedSlope) > 5000.0)
+		return 1.0;
+	
+	vec2 offsetScale = vec2(3.0 / sampleZ);
+	
+	mat2 rmat = randomRotation(tex);
+		
+	int i;
+	for (i = 0; i < 3; i++)
+	{
+		vec2 offset = rmat * poissonDisc[i] * offsetScale;
+		float sampleZ2 = zFar * getLinearDepth(depthMap, tex + offset, zFarDivZNear);
+
+		if (abs(sampleZ - sampleZ2) > 20.0)
+			result += 1.0;
+		else
+		{
+			float expectedZ = sampleZ + dot(expectedSlope, offset);
+			result += step(expectedZ - 1.0, sampleZ2);
+		}
+	}
+	
+	result *= 0.33333;
+	
+	return result;
+}
+
+void main()
+{
+	float result = ambientOcclusion(u_ScreenDepthMap, var_ScreenTex, u_ViewInfo.x, u_ViewInfo.y);
+			
+	gl_FragColor = vec4(vec3(result), 1.0);
+}