How to stack Sprites rendered inside Iterator?

Question

I am rendering an image to a Sprite inside of an Iterator. I'd like each render (iteration) to remain on the canvas indefinitely, so that each successive render layers on top of the previous ones. How can I do this? There are no Clears or any other layers in my composition.

Answer 1

In Quartz Composer, you'll almost always want to use a Clear patch — don't assume that you can rely on the prior contents of the framebuffer. So, to accomplish this, you'll need to load all of your images into a structure (probably by using JavaScript to feed an Image Loader patch and build a Queue from that), and then display all of the images each frame using an Iterator.

Check out Apple's "Image TV" sample composition, available in the OS X Developer Library in the Quartz Composer Conceptual Compositions bundle. This example demonstrates how to load a series of images into a structure and then display them.