Had an interesting problem a few days ago with Blender's texture channels. I had developed two models separately, a sign for the pedestrian zone and the tower, and wanted to bring them together (a) to see how they looked and (b) to get my workflow ironed out a bit. I am planning to develop the models separately, stage them within Blender and join them, and then import them into Unity 3D. Should be easy enough, I thought, and I was quickly able to package the image resources for the sign, import it into the tower model, and scale it to size. According to my Blender interface, things were going well:
The texured viewport indicated that, indeed, the model for the sign was where it was supposed to be and looked the way I wanted. Imagine my frustration, then, when I got this render:
The problem, which I discovered after a long time of tinkering and swearing, was with my texture channels. To simplify things a bit, I had one channel called "colormap" and the other called "bumpmap" for all my meshes. In all my models. Although Blender can keep these channels separated in individual files, once these models are imported into other models, Blender gets the channels confused. Thus, my pipe colormap being applied to my sign colormaps. I thought that each file would maybe have a unique namespace, or something like this, to avoid such a problem, but apparently not. To avoid this problem in the future, I will create unique texture channels for all models.