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90 lines
2.3 KiB
90 lines
2.3 KiB
import {
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Vector2
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} from 'three';
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/**
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* Sobel Edge Detection (see https://youtu.be/uihBwtPIBxM)
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*
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* As mentioned in the video the Sobel operator expects a grayscale image as input.
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*
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*/
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const SobelOperatorShader = {
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uniforms: {
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'tDiffuse': { value: null },
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'resolution': { value: new Vector2() }
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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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uniform vec2 resolution;
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varying vec2 vUv;
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void main() {
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vec2 texel = vec2( 1.0 / resolution.x, 1.0 / resolution.y );
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// kernel definition (in glsl matrices are filled in column-major order)
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const mat3 Gx = mat3( -1, -2, -1, 0, 0, 0, 1, 2, 1 ); // x direction kernel
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const mat3 Gy = mat3( -1, 0, 1, -2, 0, 2, -1, 0, 1 ); // y direction kernel
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// fetch the 3x3 neighbourhood of a fragment
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// first column
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float tx0y0 = texture2D( tDiffuse, vUv + texel * vec2( -1, -1 ) ).r;
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float tx0y1 = texture2D( tDiffuse, vUv + texel * vec2( -1, 0 ) ).r;
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float tx0y2 = texture2D( tDiffuse, vUv + texel * vec2( -1, 1 ) ).r;
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// second column
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float tx1y0 = texture2D( tDiffuse, vUv + texel * vec2( 0, -1 ) ).r;
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float tx1y1 = texture2D( tDiffuse, vUv + texel * vec2( 0, 0 ) ).r;
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float tx1y2 = texture2D( tDiffuse, vUv + texel * vec2( 0, 1 ) ).r;
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// third column
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float tx2y0 = texture2D( tDiffuse, vUv + texel * vec2( 1, -1 ) ).r;
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float tx2y1 = texture2D( tDiffuse, vUv + texel * vec2( 1, 0 ) ).r;
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float tx2y2 = texture2D( tDiffuse, vUv + texel * vec2( 1, 1 ) ).r;
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// gradient value in x direction
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float valueGx = Gx[0][0] * tx0y0 + Gx[1][0] * tx1y0 + Gx[2][0] * tx2y0 +
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Gx[0][1] * tx0y1 + Gx[1][1] * tx1y1 + Gx[2][1] * tx2y1 +
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Gx[0][2] * tx0y2 + Gx[1][2] * tx1y2 + Gx[2][2] * tx2y2;
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// gradient value in y direction
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float valueGy = Gy[0][0] * tx0y0 + Gy[1][0] * tx1y0 + Gy[2][0] * tx2y0 +
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Gy[0][1] * tx0y1 + Gy[1][1] * tx1y1 + Gy[2][1] * tx2y1 +
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Gy[0][2] * tx0y2 + Gy[1][2] * tx1y2 + Gy[2][2] * tx2y2;
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// magnitute of the total gradient
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float G = sqrt( ( valueGx * valueGx ) + ( valueGy * valueGy ) );
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gl_FragColor = vec4( vec3( G ), 1 );
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}`
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};
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export { SobelOperatorShader };
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