I am trying to extract some built-in and custom render passes from SceneKit, so that I can pass them into a metal pipeline and do some additional work with them.
I have a metal viewport, and have instantiated a SCNRenderer so that I can render a SCNScene using SceneKit to a texture as part of my metal draw pass. This works as expected.
Now I want to output multiple textures from the SceneKit render, not just the final color. I want to extract Depth, Normal, Lighting, Colour and a custom SCNTechnique for world position.
I can easily use a SCNTechnique to render one of these to the color output, but it's not clear how I would render multiple passes in one render call.
Is there some way to pass a writeable buffer/texture to a SCNTechnique, so that I can populate it in my SCNTechnique shader at render time with the output from the pass? Similar to how one would bind a buffer for a metal shader. SCNTechnique obfuscates things, so it's not clear how to proceed.
Does anyone have any ideas?