three-shaders
Version:
three-shaders - a library of shaders included with Three.js library
109 lines (63 loc) • 1.91 kB
JavaScript
/**
* @author alteredq / http://alteredqualia.com/
*
* Convolution shader
* ported from o3d sample to WebGL / GLSL
* http://o3d.googlecode.com/svn/trunk/samples/convolution.html
*/
var THREE = require('three');
function ConvolutionShader() {
return {
defines: {
KERNEL_SIZE_FLOAT: 25.0,
KERNEL_SIZE_INT: 25
},
uniforms: {
tDiffuse: { value: null },
uImageIncrement: { value: new THREE.Vector2( 0.001953125, 0.0 ) },
cKernel: { 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 );
}
`,
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;
}
`,
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;
}
}
};
module.exports = ConvolutionShader;