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public/sdk/three/jsm/shaders/FreiChenShader.js

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+import {
+	Vector2
+} from 'three';
+
+/**
+ * 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)
+ */
+
+const FreiChenShader = {
+
+	name: 'FreiChenShader',
+
+	uniforms: {
+
+		'tDiffuse': { value: null },
+		'aspect': { value: new Vector2( 512, 512 ) }
+	},
+
+	vertexShader: /* glsl */`
+
+		varying vec2 vUv;
+
+		void main() {
+
+			vUv = uv;
+			gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
+
+		}`,
+
+	fragmentShader: /* glsl */`
+
+		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 https://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);
+		}`
+
+};
+
+export { FreiChenShader };