trying to figure out how I can render a shadow on an invisible plane, so the background of my sceneView shows through.
THREE.js has a ShadowMaterial which does exactly this - only the shadow is rendered.
Current thinking is to make a custom Metal shader which looks straightforward, but i'm unsure how to go about knocking out the floor to show everything aside from the shadow.
Here's an example of a shadow catcher: https://knowledge.autodesk.com/search-result/caas/sfdcarticles/sfdcarticles/Maya-2015-Shadow-Catching-with-Use-Background-material.html