ARKit – Rendering a 3D object under an invisible plane

Question

I have an ARKit scene with an invisible SCNPlane:

plane.geometry?.firstMaterial?.colorBufferWriteMask = []

This plane is placed on

Answer 1

You can achieve it using the following lines of code:

shadowsPlane.geometry?.materials.first?.writesToDepthBuffer = true
shadowsPlane.geometry?.materials.first?.readsFromDepthBuffer = true

Choose one of two instance properties for .colorBufferWriteMask:

shadowsPlane.geometry?.materials.first?.colorBufferWriteMask = []

Set a rendering order for your objects like:

shadowsPlane.renderingOrder = -1   // the nearest layer

And, of course, use an appropriate .lightingModel instance property:

shadowsPlane.geometry?.materials.first?.lightingModel = .constant 

Remember, there will be some tiny air gap between two planes:

shadowsPlane.position = SCNVector3(x: 0, y: 0, z: 0)
floorPlane.position = SCNVector3(x: 0, y: -0.01, z: 0)