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<?xml version="1.0" encoding="UTF-8" ?>
<Effect>
<MetaData>
<Property name="FilterSize" formalName="Filter Size" description="Range to shoot samples for conversion" default="4"/>
<Property name="DistScale" formalName="Distance Scale" description="Divisor for distances during filtering -- larger equals more subtle" default="8"/>
<Property name="DistBias" formalName="Distance Bias" description="Depth bias to prevent self-shadowing artifacts" default="1"/>
<Property name="DebugView" formalName="Debug SSAO effect" type="Boolean" description="Allows you to see the effect of the filter directly to help setup parameters" default="False"/>
<Property name="DepthSampler" type="Texture" filter="nearest" clamp="clamp"/>
<Property name="SourceSampler" type="Texture" filter="linear" clamp="clamp"/>
</MetaData>
<Shaders>
<Shader name="SSAO">
<FragmentShader>
#include "depthpass.glsllib"
uniform vec2 CameraClipRange;
void frag( void )
{
float ret = 16.0;
vec3 kernel[16];
// Not particularly random set of samples, I know, which means some risk
// of artifacts due to regularity.
kernel[0] = vec3(0.355512, -0.709318, -0.102371);
kernel[1] = vec3(0.534186, 0.71511, -0.115167);
kernel[2] = vec3(-0.87866, 0.157139, -0.115167);
kernel[3] = vec3(0.140679, -0.475516, -0.0639818);
kernel[4] = vec3(-0.0796121, 0.158842, -0.677075);
kernel[5] = vec3(-0.0759516, -0.101676, -0.483625);
kernel[6] = vec3(0.12493, -0.0223423, -0.483625);
kernel[7] = vec3(-0.0720074, 0.243395, -0.967251);
kernel[8] = vec3(-0.207641, 0.414286, 0.187755);
kernel[9] = vec3(-0.277332, -0.371262, 0.187755);
kernel[10] = vec3(0.63864, -0.114214, 0.262857);
kernel[11] = vec3(-0.184051, 0.622119, 0.262857);
kernel[12] = vec3(0.110007, -0.219486, 0.435574);
kernel[13] = vec3(0.235085, 0.314707, 0.696918);
kernel[14] = vec3(-0.290012, 0.0518654, 0.522688);
kernel[15] = vec3(0.0975089, -0.329594, 0.609803);
ivec2 iCoords = ivec2( gl_FragCoord.xy + vec2(0.5, 0.5) );
float depth = getDepthValue(texelFetch(DepthSampler, iCoords, 0), CameraClipRange);
depth = depthValueToLinearDistance( depth, CameraClipRange );
for( int i = 15; i >= 0; --i )
{
// Note -- this cheap 2D trick is partially correct, but what we really need is to
// get the actual position, shoot the ray in 3d and re-project to get the actual
// 3D distance between points.
vec3 ray = kernel[i] * FilterSize;
ivec2 newSamp = ivec2( iCoords + ray.xy );
float sampleDepth = getDepthValue( texelFetch(DepthSampler, newSamp, 0), CameraClipRange );
sampleDepth = depthValueToLinearDistance( sampleDepth, CameraClipRange );
// Occlusion is applied based on a Cauchy distribution filter
float occlDist = max(sampleDepth - depth - DistBias, 0.0) / DistScale;
// This gives us an occlusion based on distance where the closest stuff
// occludes the most, but the extra little subtraction of a yet tighter
// Cauchy lobe means that we avoid the super-close stuff in order to limit
// self occlusion. The 1.5 multiplier is to assure that the maximum possible
// effect of a given sample is 1.0 exactly.
float occlFactor = 1.0 / ( 1.0 + occlDist*occlDist*0.04 );
occlFactor -= 1.0 / ( 1.0 + occlDist*occlDist );
ret -= 1.5 * occlFactor;
}
ret /= 16.0;
vec4 backColor = texture2D_SourceSampler(TexCoord);
if (DebugView)
{
backColor = vec4( 1.0 );
}
gl_FragColor = vec4( ret,ret,ret, 1.0 ) * backColor;
}
</FragmentShader>
</Shader>
</Shaders>
<Passes>
<Pass shader="SSAO">
<BufferInput value="[source]" param="SourceSampler" />
<DepthInput param="DepthSampler" />
</Pass>
</Passes>
</Effect>
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