I have an interresting issue with png textures. They work well in the diffusemap channel, but when I apply the png-bitmap as a reflectionmap to the shader, the material becomes unreflective. I tested these effect with a jpg-file, no problems, the reflection was made by the jpg-bitmap.
How is the resolution of the mappings handled? For example I have a very high resolution mapping, do I get the RT-feedback about the full resolution of the bitmap, or is there a downsampling made by RT?
There is no downsampling performed by the RT engine currently, it uses the textures directly. This may cause some slowdown for initial startup of the scene, especially if many large textures need to be loaded, so we will be looking at options to optimize this (perhaps using the bitmap proxy functions of 3ds Max itself).
For the reflection map, just tested quickly with RGB and greyscale PNG images in the reflection slot, and that seems to work fine. Perhaps there is something else that is specific for your scene. If you can get me the material in question to vlado@chaosgroup.com I will be able to tell you more.