So far, I told about exporting an mi file. Now here is the shader conversion for iray.
iray supports mia_material. To reuse current scenes, it is nice if I could convert the 3dsmax shaders to mia_material (Arch&Design) shader. I could imagine that some of other shaders will be supported also, but, iray is a CUDA program. CUDA has a divergence problem, it means, if many kind of shaders are in the scene, the performance becomes low. That's natural. A shader is a function and many different shaders are running on a CUDA device, I could see it will be slow. But, if the same function everywhere, then CUDA works well. (in theory. If function itself has a lot of branches, then there is a problem. Though many obstacles are there, but many kind of shaders seems to have not so chance. ) Also I imagine there is less trouble if I use the mental images native supported shaders since iray is a new renderer. In my personal opinion, I would convert the shaders.
You can find 3dsmax shaders to mia_material convert 3dsmax script here (https://code.google.com/p/shitohichi-tools/source/browse/#hg/mentalray/max2mia_material). This is based on Zap's VRay shader to mia_material converter (http://mentalraytips.blogspot.com/). Thank you, Zap. You can find two scripts. The main script is yh_max2mia_material.ms. Open this and evaluate, then the shaders in the scene will be converted. (yh_material_object_map.ms is a collection of subroutines. Therefore, this script is also needed.)
Of course, automatic conversion never be perfect. Some will fail. But, I think this is a good start point if there are many shaders in your scene.
From next week, SIGGRAPH starts. (I've never been SIGGRAPH.) I assume there is some iray demo there.
I concludes the shader conversion story here, at least this moment.