How can I take the contents (i.e. the stroke and fill) of a CAShapeLayer and draw it into an MTLTexture, which can then be displayed with a normal vertex/fragment shader?

For better memory usage when working with MTLTextures (editing + displaying in render passes, compute shaders, etc.) is it possible to save the texture to the app's Documents folder, and then use an UnsafeMutablePointer to access/modify the contents of the texture before displaying in a render pass? And would this be performant (i.e 60fps)? That way the texture won't be directly in memory all the time, but the contents can still be edited and displayed when needed.

Where can I find documentation, example projects, or video tutorials on how to work with Core Video and Metal?