import { Vector2 } from 'three'; /** * Sobel Edge Detection (see https://youtu.be/uihBwtPIBxM) * * As mentioned in the video the Sobel operator expects a grayscale image as input. * */ const SobelOperatorShader = { uniforms: { 'tDiffuse': { value: null }, 'resolution': { value: new Vector2() } }, vertexShader: /* glsl */` varying vec2 vUv; void main() { vUv = uv; gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 ); }`, fragmentShader: /* glsl */` 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 ); }` }; export { SobelOperatorShader };