KTX textures crash the classic OpenGL renderer and the Python viewer with
"Number of channels not supported: 1": mjCTexture::LoadKTX stores the file as
an opaque single-channel blob for the Filament renderer, and mjr_uploadTexture
aborts via mju_error because the classic path only handles 3- or 4-channel
textures.
Skip textures the classic renderer can't upload (nchannel not 3 or 4) with a
warning instead of aborting, so the model still loads and the other textures
render. LoadKTX and the Filament path are unchanged. The guard also covers the
cube/skybox path, which previously over-read a single-channel blob as RGB.
Add a render_test.py regression test that builds a model with a KTX texture and
constructs an MjrContext; it aborts before this change and passes after.
Addresses #3343.
Anas
ce025f0ec3