import THREE from 'three'
/**
 * @author zz85 / https://github.com/zz85 | https://www.lab4games.net/zz85/blog
 *
 * Edge Detection Shader using Sobel filter
 * Based on http://rastergrid.com/blog/2011/01/frei-chen-edge-detector
 *
 * aspect: vec2 of (1/width, 1/height)
 */

let EdgeShader3 = {

    uniforms: {

        "tDiffuse": { type: "t", value: null },
        "aspect":    { type: "v2", value: new THREE.Vector2( 512, 512 ) },
    },

    vertexShader: [

        "varying vec2 vUv;",

        "void main() {",

            "vUv = uv;",
            "gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );",

        "}"

    ].join("\n"),

    fragmentShader: [

        "uniform sampler2D tDiffuse;",
        "varying vec2 vUv;",
        "uniform vec2 aspect;",


        "vec2 texel = vec2(1.0 / aspect.x, 1.0 / aspect.y);",

        "mat3 G[2];",

        "const mat3 g0 = mat3( 1.0, 2.0, 1.0, 0.0, 0.0, 0.0, -1.0, -2.0, -1.0 );",
        "const mat3 g1 = mat3( 1.0, 0.0, -1.0, 2.0, 0.0, -2.0, 1.0, 0.0, -1.0 );",


        "void main(void)",
        "{",
            "mat3 I;",
            "float cnv[2];",
            "vec3 sample;",

            "G[0] = g0;",
            "G[1] = g1;",

            /* 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<2; 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; ",
            "}",

            "gl_FragColor = vec4(0.5 * sqrt(cnv[0]*cnv[0]+cnv[1]*cnv[1]));",
        "} ",

    ].join("\n")

}

export default EdgeShader3