A common trick is to call
background() with a non-full opacity argument, in
order to leave a trail. This works when everything on the canvas should leave a
trail. How about when only some objects should leave a trail?
One solution is to use an Array, in order to re-draw all the elements of the trail each time the canvas is erased. (This example demonstrates this technique.) Another is to draw the object that leaves a trail in its own layer. That’s what this example does. (This example demonstrates the same technique without the p5.layer library.)
Another example of using a Graphics in order for one object to allow one object to leave a trail, while the rest of the canvas is fully erased.
Using two layers in order to slice an sketch into two rectangles, that can be moved independently.
In this example,
enterLayer() is only used to temporarily replace the p5.js
graphics commands. The sketch itself is responsible for creating and drawing the
enterLayer() with two different keys, in order to create two Graphics
that are drawn side by side.