Stroke Width with a SceneKit line primitive type

Question

I am trying to replicate this cube image shape (with permission from the original creator) using scene kit.

Answer 1

SceneKit doesn't provide controls for this. However, SceneKit draws using OpenGL ES, which does.

When you're drawing with GL in the GL_LINES mode, the glLineWidth call changes the line width. (Watch out: the argument is in actual pixels, not UI-layout points, so you'll need a larger width than you might think if you don't want super-thin hairlines on a Retina display.)

So, where do you call that in your SceneKit app? You have a few options there. In a simple scene like yours, where you're only rendering one thing, you can just set it before the scene renders. Set a delegate for your view, then implement renderer:willRenderSceneAtTime: and call glLineWidth there.

However, OpenGL line rendering is pretty limited — if you want to customize rendering more, you'll need a different approach. Just which approach works best depends on exactly what you're going for, so here are a few ideas for you to research:

• Make your "lines" from narrow triangle strips
• Make them from primitive SCN geometries like boxes and cylinders
• Keep a simple cube geometry, but use a fragment shader (or shader modifier snippet) to draw only near the edges of each polygon