Transmissive Material Causes Incorrect CubeCamera Output

[drbct]

Description

Hey! While integrating transmissive materials into our workflow, we ran into a possible bug with the CubeCamera which is described below.

Reproduction steps

1. Open the live example. The scene shows a RoomEnvironment, a CubeCamera whose output has been set as the envMap of a sphere, an opaque floor and a thin cuboid with a transmissive material.
2. Observe that one face of the cube map is black and another one has noticeable seams. It appears as though the face with the seams would fit perfectly in place of the black face.
3. Disable transmission in line 35.
4. Observe that the artifacts are gone.

Code

This is the object which seems to cause the faulty behavior:

const glass = new THREE.Mesh(
    new THREE.BoxGeometry(2.0, 2.0, 0.01, 1, 1, 1),
    new THREE.MeshPhysicalMaterial({
        color: new THREE.Color(1.0, 1.0, 1.0),
        metalness: 0.0,
        roughness: 1.0,
        transmission: 1.0
    })
);

Live example

https://jsfiddle.net/k1t9b58L/33/

Screenshots

Version

r176

Device

Desktop

Browser

Chrome

OS

Linux