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94 lines
2.9 KiB
94 lines
2.9 KiB
2 years ago
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( function () {
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/**
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* Edge Detection Shader using Frei-Chen filter
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* Based on http://rastergrid.com/blog/2011/01/frei-chen-edge-detector
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*
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* aspect: vec2 of (1/width, 1/height)
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*/
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const FreiChenShader = {
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uniforms: {
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'tDiffuse': {
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value: null
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},
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'aspect': {
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value: new THREE.Vector2( 512, 512 )
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}
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},
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vertexShader: /* glsl */`
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varying vec2 vUv;
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void main() {
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vUv = uv;
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gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
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}`,
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fragmentShader: /* glsl */`
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uniform sampler2D tDiffuse;
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varying vec2 vUv;
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uniform vec2 aspect;
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vec2 texel = vec2( 1.0 / aspect.x, 1.0 / aspect.y );
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mat3 G[9];
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// hard coded matrix values!!!! as suggested in https://github.com/neilmendoza/ofxPostProcessing/blob/master/src/EdgePass.cpp#L45
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const mat3 g0 = mat3( 0.3535533845424652, 0, -0.3535533845424652, 0.5, 0, -0.5, 0.3535533845424652, 0, -0.3535533845424652 );
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const mat3 g1 = mat3( 0.3535533845424652, 0.5, 0.3535533845424652, 0, 0, 0, -0.3535533845424652, -0.5, -0.3535533845424652 );
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const mat3 g2 = mat3( 0, 0.3535533845424652, -0.5, -0.3535533845424652, 0, 0.3535533845424652, 0.5, -0.3535533845424652, 0 );
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const mat3 g3 = mat3( 0.5, -0.3535533845424652, 0, -0.3535533845424652, 0, 0.3535533845424652, 0, 0.3535533845424652, -0.5 );
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const mat3 g4 = mat3( 0, -0.5, 0, 0.5, 0, 0.5, 0, -0.5, 0 );
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const mat3 g5 = mat3( -0.5, 0, 0.5, 0, 0, 0, 0.5, 0, -0.5 );
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const mat3 g6 = mat3( 0.1666666716337204, -0.3333333432674408, 0.1666666716337204, -0.3333333432674408, 0.6666666865348816, -0.3333333432674408, 0.1666666716337204, -0.3333333432674408, 0.1666666716337204 );
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const mat3 g7 = mat3( -0.3333333432674408, 0.1666666716337204, -0.3333333432674408, 0.1666666716337204, 0.6666666865348816, 0.1666666716337204, -0.3333333432674408, 0.1666666716337204, -0.3333333432674408 );
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const mat3 g8 = mat3( 0.3333333432674408, 0.3333333432674408, 0.3333333432674408, 0.3333333432674408, 0.3333333432674408, 0.3333333432674408, 0.3333333432674408, 0.3333333432674408, 0.3333333432674408 );
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void main(void)
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{
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G[0] = g0,
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G[1] = g1,
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G[2] = g2,
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G[3] = g3,
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G[4] = g4,
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G[5] = g5,
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G[6] = g6,
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G[7] = g7,
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G[8] = g8;
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mat3 I;
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float cnv[9];
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vec3 sample;
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/* fetch the 3x3 neighbourhood and use the RGB vector's length as intensity value */
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for (float i=0.0; i<3.0; i++) {
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for (float j=0.0; j<3.0; j++) {
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sample = texture2D(tDiffuse, vUv + texel * vec2(i-1.0,j-1.0) ).rgb;
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I[int(i)][int(j)] = length(sample);
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}
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}
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/* calculate the convolution values for all the masks */
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for (int i=0; i<9; i++) {
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float dp3 = dot(G[i][0], I[0]) + dot(G[i][1], I[1]) + dot(G[i][2], I[2]);
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cnv[i] = dp3 * dp3;
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}
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float M = (cnv[0] + cnv[1]) + (cnv[2] + cnv[3]);
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float S = (cnv[4] + cnv[5]) + (cnv[6] + cnv[7]) + (cnv[8] + M);
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gl_FragColor = vec4(vec3(sqrt(M/S)), 1.0);
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}`
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};
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THREE.FreiChenShader = FreiChenShader;
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} )();
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