Multisampling effectively disables Depth Texture

[vanruesc]

Describe the bug

WebGLMultisampleRenderTarget was removed in #23455 and the functionality was added to WebGLRenderTarget with the new samples property. However, when using a DepthTexture attachment on a render target with multisampling enabled, the depth texture remains empty because depth is being invalidated for performance reasons regarding WebXR. This behaviour was the same with WebGLMultisampleRenderTarget, but that class had an undocumented ignoreDepthForMultisampleCopy property that allowed to preserve depth. I don't think this property was carried over in r138.

To Reproduce

Steps to reproduce the behavior:

1. Render a scene into a multisample render target that has a depth texture attachment.
2. Render the contents of the depth texture to screen.
3. See empty image.

Live example

Uncomment line 60 in index.js: Sandbox

Expected behavior

Depth should be preserved if the multisample render target has a depth texture attachment.

Platform:

• Device: Desktop
• OS: Linux
• Browser: Firefox (white screen), Brave (black screen)
• Three.js version: r138

[Mugen87]

I think we can fix this issue by changing the following line:

three.js/src/renderers/webgl/WebGLTextures.js

Line 1697 in 62c6fab

const ignoreDepthValues = ( renderTargetProperties.__ignoreDepthValues !== undefined ) ? renderTargetProperties.__ignoreDepthValues : true;

If __ignoreDepthValues is undefined, the line returns false. That should solve the issue.