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| /** | |
| * @author Mugen87 / https://github.com/Mugen87 | |
| * | |
| * Sobel Edge Detection (see https://youtu.be/uihBwtPIBxM) | |
| * | |
| * As mentioned in the video the Sobel operator expects a grayscale image as input. | |
| * | |
| */ | |
| THREE.SobelOperatorShader = { | |
| uniforms: { | |
| "tDiffuse": { value: null }, | |
| "resolution": { value: new THREE.Vector2() } | |
| }, | |
| vertexShader: [ | |
| "varying vec2 vUv;", | |
| "void main() {", | |
| "vUv = uv;", | |
| "gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );", | |
| "}" | |
| ].join( "\n" ), | |
| fragmentShader: [ | |
| "uniform sampler2D tDiffuse;", | |
| "uniform vec2 resolution;", | |
| "varying vec2 vUv;", | |
| "void main() {", | |
| "vec2 texel = vec2( 1.0 / resolution.x, 1.0 / resolution.y );", | |
| // kernel definition (in glsl matrices are filled in column-major order) | |
| "const mat3 Gx = mat3( -1, -2, -1, 0, 0, 0, 1, 2, 1 );", // x direction kernel | |
| "const mat3 Gy = mat3( -1, 0, 1, -2, 0, 2, -1, 0, 1 );", // y direction kernel | |
| // fetch the 3x3 neighbourhood of a fragment | |
| // first column | |
| "float tx0y0 = texture2D( tDiffuse, vUv + texel * vec2( -1, -1 ) ).r;", | |
| "float tx0y1 = texture2D( tDiffuse, vUv + texel * vec2( -1, 0 ) ).r;", | |
| "float tx0y2 = texture2D( tDiffuse, vUv + texel * vec2( -1, 1 ) ).r;", | |
| // second column | |
| "float tx1y0 = texture2D( tDiffuse, vUv + texel * vec2( 0, -1 ) ).r;", | |
| "float tx1y1 = texture2D( tDiffuse, vUv + texel * vec2( 0, 0 ) ).r;", | |
| "float tx1y2 = texture2D( tDiffuse, vUv + texel * vec2( 0, 1 ) ).r;", | |
| // third column | |
| "float tx2y0 = texture2D( tDiffuse, vUv + texel * vec2( 1, -1 ) ).r;", | |
| "float tx2y1 = texture2D( tDiffuse, vUv + texel * vec2( 1, 0 ) ).r;", | |
| "float tx2y2 = texture2D( tDiffuse, vUv + texel * vec2( 1, 1 ) ).r;", | |
| // gradient value in x direction | |
| "float valueGx = Gx[0][0] * tx0y0 + Gx[1][0] * tx1y0 + Gx[2][0] * tx2y0 + ", | |
| "Gx[0][1] * tx0y1 + Gx[1][1] * tx1y1 + Gx[2][1] * tx2y1 + ", | |
| "Gx[0][2] * tx0y2 + Gx[1][2] * tx1y2 + Gx[2][2] * tx2y2; ", | |
| // gradient value in y direction | |
| "float valueGy = Gy[0][0] * tx0y0 + Gy[1][0] * tx1y0 + Gy[2][0] * tx2y0 + ", | |
| "Gy[0][1] * tx0y1 + Gy[1][1] * tx1y1 + Gy[2][1] * tx2y1 + ", | |
| "Gy[0][2] * tx0y2 + Gy[1][2] * tx1y2 + Gy[2][2] * tx2y2; ", | |
| // magnitute of the total gradient | |
| "float G = sqrt( ( valueGx * valueGx ) + ( valueGy * valueGy ) );", | |
| "gl_FragColor = vec4( vec3( G ), 1 );", | |
| "}" | |
| ].join( "\n" ) | |
| }; | |