playcanvas/scripts/posteffects/posteffect-luminosity.js

PlayCanvas WebGL game engine

// --------------- POST EFFECT DEFINITION --------------- //
/**
 * @class
 * @name LuminosityEffect
 * @classdesc Outputs the luminosity of the input render target.
 * @description Creates new instance of the post effect.
 * @augments PostEffect
 * @param {GraphicsDevice} graphicsDevice - The graphics device of the application.
 */
function LuminosityEffect(graphicsDevice) {
    pc.PostEffect.call(this, graphicsDevice);

    var fshader = [
        'uniform sampler2D uColorBuffer;',
        '',
        'varying vec2 vUv0;',
        '',
        'void main() {',
        '    vec4 texel = texture2D(uColorBuffer, vUv0);',
        '    vec3 luma = vec3(0.299, 0.587, 0.114);',
        '    float v = dot(texel.xyz, luma);',
        '    gl_FragColor = vec4(v, v, v, texel.w);',
        '}'
    ].join('\n');

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

LuminosityEffect.prototype = Object.create(pc.PostEffect.prototype);
LuminosityEffect.prototype.constructor = LuminosityEffect;

Object.assign(LuminosityEffect.prototype, {
    render: function (inputTarget, outputTarget, rect) {
        var device = this.device;
        var scope = device.scope;

        scope.resolve('uColorBuffer').setValue(inputTarget.colorBuffer);
        this.drawQuad(outputTarget, this.shader, rect);
    }
});

// ----------------- SCRIPT DEFINITION ------------------ //
var Luminosity = pc.createScript('luminosity');

// initialize code called once per entity
Luminosity.prototype.initialize = function () {
    this.effect = new LuminosityEffect(this.app.graphicsDevice);

    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);
    });
};