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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 };
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