The background outside the glass also looks white here, perhaps you have fog enabled? The subset of code you’ve shared looks fine, but isn’t enough to reproduce the issue.
Yes i see the same as in your image. The main thing that bothers me is that im using the fog and the background for a seemless background. With the glass the seemless background does not work… is there another way to achieve this?
If mpm doesn’t support fog have you tried meshTransmissionMaterial? Though … it’s probably the same because it’s based on the same shader but maybe worth testing.
mtm works. this seems to be a bug in threejs/mpm, probably a recent one as i’ve never seen that before, and it would explain why drei works as it bases on physical from a few months ago and hasn’t been touched since then.