https://github.com/WWBN/AVideo/issues/8713

node_modules/three/examples/js/shaders/SobelOperatorShader.js

@@ -0,0 +1,88 @@
+/**
+ * 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' )
+
+};