Alpha Gradient

by roomyrooms

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/pixi.js/5.2.2/pixi.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/pixi-filters@latest/dist/pixi-filters.js"></script>
<script type="x-data-url" id="tree-url">
 ...

JavaScript

var treeUrl = document.getElementById('tree-url').textContent;
var treeImg = document.getElementById('tree-preview');

treeImg.src = treeUrl;

var fragmentShader = `
precision mediump float;

varying vec2 vTextureCoord;

uniform sampler2D uSampler;
uniform highp vec4 inputSize;
uniform highp vec4 outputFrame;

uniform vec2 lightDist;
uniform float time;

void main() {
  vec2 f = vTextureCoord * inputSize.xy / outputFrame.zw;
  vec4 color = texture2D(uSampler, vTextureCoord);
  float dist = 1.0-distance(f,lightDist);
  float adjDist = dist * clamp(smoothstep(0.75, 1.0, lightDist.y),0.1,0.8);
  gl_FragColor = color * adjDist;
}`

function defaultValue(inputValue, defaultValue) {
    inputValue = typeof inputValue !== 'undefined' ? inputValue : defaultValue;
    return inputValue;
}


function LightFilter(lightDist) {
    PIXI.Filter.call(this,undefined,fragmentShader);
    this.uniforms.lightDist = defaultValue(lightDist,[0,0]);
    this.uniforms.time = performance.now();
}

LightFilter.prototype = Object.create(PIXI.Filter.prototype);
LightFilter.prototype.constructor = LightFilter;

LightFilter.prototype.apply = function (filterManager, input, output, clear) {
		clear = PIXI.CLEAR_MODES;
    this.uniforms.time = performance.now();
    // draw the filter...
    filterManager.applyFilter(this, input, output);
}

var stage = new PIXI.Container();

// create a renderer instance.
var renderer = PIXI.autoDetectRenderer(512, 512);
renderer.roundPixels = true;
PIXI.settings.SCALE_MODE = PIXI.SCALE_MODES.NEAREST;

// tex creation
var treeBaseTexture = new PIXI.BaseTexture(treeImg);
var treeTexture = new PIXI.Texture(treeBaseTexture);
var treeSprite = new PIXI.Sprite(treeTexture);
var treeBaseTexture = new PIXI.BaseTexture(treeImg);
var treeTexture = new PIXI.Texture(treeBaseTexture);
var treeSprite = new PIXI.Sprite(treeTexture);

// ADDITIVE blend mode for pretty intersecting lights

// move a little bit one light on right to check proper lights intersect
treeSprite.x =...