Pixi.js v5 - apply alpha to displacement map - pixi.js

Question

I'm scaling a displacement map on click but would like that map to fade away once it reaches almost full scale. The idea is that the filter should be non-existent after a couple of seconds.
const app = new PIXI.Application({
view: document.querySelector("#canvas"),
width: 512,
height: 512
});
const logo = PIXI.Sprite.fromImage("https://unsplash.it/600");
const displacement = PIXI.Sprite.fromImage("https://images.unsplash.com/photo-1541701494587-cb58502866ab?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&w=1000&q=80");
const filter = new PIXI.filters.DisplacementFilter(displacement);
logo.anchor.set(0.5);
logo.position.set(256);
logo.interactive = true;
displacement.anchor.set(0.5);
displacement.position.set(256);
displacement.scale.set(0.05)
displacement.alpha = 1
app.stage.filterArea = app.screen;
app.stage.filters = [filter];
app.stage.addChild(logo, displacement);
app.ticker.add(function() {
displacement.scale.x += 0.05
displacement.scale.y += 0.05
if (displacement.scale.x > 10) app.ticker.stop()
});
logo.on('mousedown', function() {
displacement.scale.set(0.05)
app.ticker.start()
});
Here's what I have so far:
https://codepen.io/mariojankovic/pen/pojjNae?editors=0111

Answer 1

I've only just started looking at Pixi but I think you want to use the scale property of the displacement filter. This value says how far to shift. Reducing this value to 0 will lessen its effect to none.
https://pixijs.download/dev/docs/PIXI.filters.DisplacementFilter.html
https://pixijs.download/dev/docs/PIXI.filters.DisplacementFilter.html#scale
The way it works is it uses the values of the displacement map to look
up the correct pixels to output. This means it's not technically
moving the original. Instead, it's starting at the output and asking
"which pixel from the original goes here". For example, if a
displacement map pixel has red = 1 and the filter scale is 20, this
filter will output the pixel approximately 20 pixels to the right of
the original.
https://codepen.io/PAEz/pen/BaoREwv
const app = new PIXI.Application({
view: document.querySelector("#canvas"),
width: 512,
height: 512
});
const logo = PIXI.Sprite.fromImage("https://unsplash.it/600");
const displacement = PIXI.Sprite.fromImage(
"https://images.unsplash.com/photo-1541701494587-cb58502866ab?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&w=1000&q=80"
);
const filter = new PIXI.filters.DisplacementFilter(displacement);
logo.anchor.set(0.5);
logo.position.set(256);
logo.interactive = true;
displacement.anchor.set(0.5);
displacement.position.set(256);
displacement.scale.set(0.0);
displacement.alpha = 1;
app.stage.filterArea = app.screen;
app.stage.filters = [filter];
app.stage.addChild(logo, displacement);
const displacementScaleFrom = 0.05;
const displacementScaleTo = 10 ;
const displacementStep = 0.05;
const filterScaleFrom = 20;// the default value for the filter is 20
const filterStep = filterScaleFrom / ((displacementScaleTo-displacementScaleFrom) / displacementStep);
app.ticker.add(function () {
displacement.scale.x += displacementStep;
displacement.scale.y += displacementStep;
filter.scale.x -= filterStep;
filter.scale.y -= filterStep;
if (displacement.scale.x >= displacementScaleTo) {
app.ticker.stop();
filter.scale.x = 0;
filter.scale.y = 0;
}
});
logo.on("mousedown", function () {
displacement.scale.set(displacementScaleFrom);
filter.scale.x = filterScaleFrom;
filter.scale.y = filterScaleFrom;
app.ticker.start();
});