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mobile-query-three-vendor-three.js-shaders-EdgeShader.js / js



  

author: zz85 / github.com/zz85 | www.lab4games.net/zz85/blog 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)

  
  
  THREE.EdgeShader = {
  
          uniforms: {
  
                  "tDiffuse": { type: "t", value: null },
                  "aspect":    { type: "v2", value: new THREE.Vector2( 512, 512 ) },
          },
  
          vertexShader: [
  
                  "varying vec2 vUv;",
  
                  "void main() {",
  
                          "vUv = uv;",
                          "gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );",
  
                  "}"
  
          ].join("\n"),
  
          fragmentShader: [
  
                  "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 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);",
                  "}",
  
          ].join("\n")
  };
  


(C) Æliens 04/09/2009

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