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