playcanvas/scripts/posteffects/posteffect-edgedetect.js

Open-source WebGL/WebGPU 3D engine for the web

// --------------- POST EFFECT DEFINITION --------------- //
/**
 * @class
 * @name EdgeDetectEffect
 * @classdesc Edge Detection post effect using Sobel filter.
 * @description Creates new instance of the post effect.
 * @augments PostEffect
 * @param {GraphicsDevice} graphicsDevice - The graphics device of the application.
 */
class EdgeDetectEffect extends pc.PostEffect {
    constructor(graphicsDevice) {
        super(graphicsDevice);

        const fshader = /* glsl */`
            uniform sampler2D uColorBuffer;
            varying vec2 vUv0;
            uniform vec2 uResolution;
            uniform float uIntensity;
            uniform vec4 uColor;

            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(uColorBuffer, vUv0 + uResolution * 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 = uIntensity * uColor * vec4(sqrt(cnv[0]*cnv[0]+cnv[1]*cnv[1]));
            }
        `;

        this.shader = pc.ShaderUtils.createShader(graphicsDevice, {
            uniqueName: 'EdgeDetectShader',
            attributes: { aPosition: pc.SEMANTIC_POSITION },
            vertexGLSL: pc.PostEffect.quadVertexShader,
            fragmentGLSL: fshader
        });

        // Uniforms
        this.resolution = new Float32Array(2);
        this.intensity = 1.0;
        this.color = new pc.Color(1, 1, 1, 1);
    }

    render(inputTarget, outputTarget, rect) {
        const device = this.device;
        const scope = device.scope;

        this.resolution[0] = 1 / inputTarget.width;
        this.resolution[1] = 1 / inputTarget.height;
        scope.resolve('uResolution').setValue(this.resolution);
        scope.resolve('uColorBuffer').setValue(inputTarget.colorBuffer);
        scope.resolve('uColor').setValue(this.color.data);
        scope.resolve('uIntensity').setValue(this.intensity);
        this.drawQuad(outputTarget, this.shader, rect);
    }
}

// ----------------- SCRIPT DEFINITION ------------------ //
var EdgeDetect = pc.createScript('edgeDetect');

EdgeDetect.attributes.add('intensity', {
    type: 'number',
    default: 1,
    min: 0,
    max: 2,
    title: 'Intensity'
});

EdgeDetect.attributes.add('color', {
    type: 'rgba',
    default: [0.5, 0.5, 0.5, 1],
    title: 'Color'
});

// initialize code called once per entity
EdgeDetect.prototype.initialize = function () {
    this.effect = new EdgeDetectEffect(this.app.graphicsDevice);
    this.effect.intensity = this.intensity;
    this.effect.color = this.color;

    this.on('attr', function (name, value) {
        this.effect[name] = value;
    }, this);

    var queue = this.entity.camera.postEffects;

    queue.addEffect(this.effect);

    this.on('state', function (enabled) {
        if (enabled) {
            queue.addEffect(this.effect);
        } else {
            queue.removeEffect(this.effect);
        }
    });

    this.on('destroy', function () {
        queue.removeEffect(this.effect);
    });
};