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/**
* @author alteredq / http://alteredqualia.com/
*
* Convolution shader
* ported from o3d sample to WebGL / GLSL
* http://o3d.googlecode.com/svn/trunk/samples/convolution.html
*/
THREE.ConvolutionShader = {
defines: {
"KERNEL_SIZE_FLOAT": "25.0",
"KERNEL_SIZE_INT": "25",
},
uniforms: {
"tDiffuse": { type: "t", value: null },
"uImageIncrement": { type: "v2", value: new THREE.Vector2( 0.001953125, 0.0 ) },
"cKernel": { type: "fv1", value: [] }
},
vertexShader: [
"uniform vec2 uImageIncrement;",
"varying vec2 vUv;",
"void main() {",
"vUv = uv - ( ( KERNEL_SIZE_FLOAT - 1.0 ) / 2.0 ) * uImageIncrement;",
"gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );",
"}"
].join("\n"),
fragmentShader: [
"uniform float cKernel[ KERNEL_SIZE_INT ];",
"uniform sampler2D tDiffuse;",
"uniform vec2 uImageIncrement;",
"varying vec2 vUv;",
"void main() {",
"vec2 imageCoord = vUv;",
"vec4 sum = vec4( 0.0, 0.0, 0.0, 0.0 );",
"for( int i = 0; i < KERNEL_SIZE_INT; i ++ ) {",
"sum += texture2D( tDiffuse, imageCoord ) * cKernel[ i ];",
"imageCoord += uImageIncrement;",
"}",
"gl_FragColor = sum;",
"}"
].join("\n"),
buildKernel: function ( sigma ) {
// We lop off the sqrt(2 * pi) * sigma term, since we're going to normalize anyway.
function gauss( x, sigma ) {
return Math.exp( - ( x * x ) / ( 2.0 * sigma * sigma ) );
}
var i, values, sum, halfWidth, kMaxKernelSize = 25, kernelSize = 2 * Math.ceil( sigma * 3.0 ) + 1;
if ( kernelSize > kMaxKernelSize ) kernelSize = kMaxKernelSize;
halfWidth = ( kernelSize - 1 ) * 0.5;
values = new Array( kernelSize );
sum = 0.0;
for ( i = 0; i < kernelSize; ++i ) {
values[ i ] = gauss( i - halfWidth, sigma );
sum += values[ i ];
}
// normalize the kernel
for ( i = 0; i < kernelSize; ++i ) values[ i ] /= sum;
return values;
}
};
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