Description

As can be seen above the viewport still renders the entire background. The actual model geometry is however only rendered in the bottom left corner. I first noticed this on my own implementation and then double checked against your samples.

Platform

.NET 8.0
Windows 11 - 10.0.26100 Build 26100
GPU - NVIDIA T500

Reproducing

Run the Samples on a machine as described above.

Linux

I also tested on Ubuntu 22.04 and did not get this issue.

Remarks

I am aware that Windows compatibility is limited for OpenTK+Avalonia. This may be unrelated to the provided BaseClass. I will try fixing this bug and hopefully quickly create a PR.