Is there are way to draw a pixel in SpriteKit?

Question

I am trying to put together ray tracing routine and the width/shade of every pixel in a single ray will change over the length of the line. Is there a way in SpriteKit to draw a single pixel on the screen? or should I be doing this using UIImage?

Answer 1

SpriteKit isn't a pixel drawing API. It's more of a "moving pictures around on the screen" API. There are a couple of cases, though, where it makes sense to do custom drawing, and SpriteKit (as of iOS 8 and OS X 10.10) has a few facilities for this.

1. If you want to create custom art to apply to sprites, with that art being mostly static (that is, not needing to be redrawn frequently as SpriteKit animates the scene), just use the drawing API of your choice — Core Graphics, OpenGL, emacs, whatever — to create an image. Then you can stick that image in an SKTexture object to apply to sprites in your scene.

2. To directly munge the bits inside a texture, use SKMutableTexture. This doesn't really provide drawing facilities — you just get to work with the raw image data. (And while you could layer drawing tools on top of that — for example, by creating a CG image context from the data and rewriting the data with CG results — that'd slow you down too much to keep up with the animation framerate.)

3. If you need high-framerate, per-pixel drawing, your best bet is to do that entirely on the GPU. Use SKShader for that.

Answer 2

If your application is redrawing every frame, then you can use an offscreen buffer to dynamically update pixels, aka SKMutableTexture. I'm not sure how slow it will be.