RealityKit Bug?: Setting alpha of a plane's mesh material completely removes the plane/makes it invisible

Question

Created Dec ’20

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When I use MeshResource.generatePlane() to create a plane and apply transparency (any alpha < 1.0), it makes the entity completely not render in AR (suddenly disappears).

Renders as expected when alpha is set to 1.0.

Code Block let mesh = MeshResource.generatePlane(width: planeAnchor.extent.x, depth: planeAnchor.extent.z)
var material = SimpleMaterial()
material.baseColor = MaterialColorParameter.color(.init(red: 0.0, green: 1.0, blue: 1.0, alpha: 0.5 )) /* setting the alpha makes the generated plane disappear */
let modelEntity = ModelEntity(mesh: mesh, materials: [material])
let anchorEntity = AnchorEntity(anchor: planeAnchor)

Note: I'm generating the anchor entity initiated from an existing plane anchor that is classified as a wall.

Any ideas why this is occurring and potential solutions?
Thanks!

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Answer 1

maxxfrazer OP

Dec ’20

I just tried a similar bit of code out with the same color settings, but didn't have any issues:

Code Block swiftlet tanchor = AnchorEntity(world: [0, -1, -1])
var simpMat = SimpleMaterial()
simpMat.baseColor = MaterialColorParameter.color(.init(red: 0.0, green: 1.0, blue: 1.0, alpha: 0.5))
let tcube = ModelEntity(
    mesh: .generatePlane(width: 0.3, depth: 0.3),
    materials: [simpMat]
)
tanchor.addChild(tcube)
self.arView.scene.addAnchor(tanchor)

(not anchored to a wall though in this example)

Maybe try using a cube with a very small height, or another shape and see if you get the same issue?

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