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iray developer's blog

NVidia ARC's iray developers write a iray's technical blog.

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iray 5: iray in standalone mental ray

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 ...

iray 1: iray in standalone mental ray

* As far as I know, we can only run mental images' iray in NVidia's RealityServer. I hope Autodesk 3dsmax/maya/xsi supports iray soon. mental images (a subsidiary company of NVidia) demonstrated iray renderer in GDC's keynote and SIGGRAPH ASIA 2009. GDC NVidia iray demo (YouTube) mental images iray page mental ray or some other renderers can simulate indirect illumination in some extent, but the methods final gather or photon map are quite rough approximation. They have no guarantee to converge to the correct answer. Also there are many renderer parameters for performance optimisation. These parameters heavily depends on the scene. It is difficult to achieve high quality and faster rendering. These methods are anyway time consuming, therefore, we sometimes put invisible light sources by hand, that simulates indirect lights. This iray is a brute force path tracer and there is no renderer parameter, but nowadays computer has not enough power to compute the light tran...