Untextured Mesh Faces Render as Random Colors in Alpine Docker, Black on macOS

[lukakristofelc]

When processing an OBJ file with textures locally on macOS (Sequoia 15.5), any faces without an assigned texture are rendered as solid black, as shown in the image below:

However, when processing the same file with identical textures in a node:16-alpine3.17 Docker container, the untextured faces are instead filled with seemingly random colors—which vary each time the mesh is processed:

I’ve also tested other Docker images (such as bullseye and bullseye-slim), but they exhibit the same behavior with random face colors.

This discrepancy may be related to differences in the Qt5 builds used on macOS (installed via Homebrew) versus those in Alpine Linux (installed via apk). However, I haven’t yet been able to pinpoint the exact cause or reproduce one environment's behavior in the other. I'm also attaching the two processed files:

meshes.zip

[ponchio]

Right now the unassigned vertices get assigned a [0, 0] texture coords, for lack of better ideas. Depending on the packing the 0, 0 pixel should be one of the pixels of the texture (often a pixel of the background of the texture) or a pixel of the initial texture (grey 127).

It's a bit strange to see random bright colors.

Could you send me a obj sample instead (to see what 'untextured' means exactly?

[lukakristofelc]

Here is the link to the original obj file and textures: TPI-mine-crop.zip