Closes #30745

Related issue: #29779

Description

It's possible render into specific mipmap levels when we set the target.texture.mipmaps array. This works great for color-only render targets, however if we give this target a depth buffer (either through depthBuffer: true or an explicit depthTexture), rendering will fail with a crash when rendering

The crash is caused by three.js assuming .__webglFramebuffer is a single framebuffer, however, when .mipmaps is set it becomes an array:

if (texture.mipmaps && texture.mipmaps.length > 0) {
  for (let level = 0; level < texture.mipmaps.length; level++) {
    setupFrameBufferTexture(renderTargetProperties.__webglFramebuffer[level], renderTarget, texture, _gl.COLOR_ATTACHMENT0, glTextureType, level);
  }
} else {
  setupFrameBufferTexture(renderTargetProperties.__webglFramebuffer, renderTarget, texture, _gl.COLOR_ATTACHMENT0, glTextureType, 0);
}

This causes a crash on this line

And

Maybe other places too

This PR resolves this by instead setting the depth attachment for only mipmap 0.

I will also think about setting a depth attachment for each mip level

I've tried to use idomatic three.js style which comes out quite verbose but let me know if we want something tidier!