taming mental ray (English version)

Here is an Emacs mode for editing mi file ( mi-mode.el ). I found it useful.

The original mental ray camera is a pinhole camera. Therefore, some of the terminology differs with a normal camera. I will write them down here. aperture: This is the film width size. This has no relationship with lens aperture/opening. mental ray's camera was a pinhole camera, there is no lens aperture. focal: This is the distance from lens to the film (sensor). Pinhole camera always focused, so there is no focal length meaning. But using parameters aperture and focal length, we can compute the horizontal field of view. I think these two parameters exist for this purpose. aspect ratio: This is film(sensor)'s aspect ratio. There is no relationship with pixel resolution and camera geometry.  aspect ratio = film width/film height. Note: If we use aperture, focal, and aspect ratio, we can compute the vertical field of view. mental ray/iray camera model (pinhole camera) without lens shader Current mental ray/iray can have depth of field effect, etc., this termino

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

As an example in here, I create one teapot in 3dsmax and assign a mia_material (Arch&Design). Since 3dsmax exports an mi file with 3dsmax shader dependency, mental ray standalone could have a problem to render that mi file. mental ray standalone usually doesn't have 3dsmax shaders. The main advantage of the standalone mental ray is parallel rendering on a render farm. I couldn't tell the legal license of the 3dsmax shaders. For the safe side, if we have no dependency to the 3dsmax shaders, it shouldn't have a problem. (Or you can also install 3dsmax to all the render farm machine, though it doesn't make much sense.) If I just render the mi file from the 3dsmax without modifying, I see the following error. --- > ray -x on -v 5 00teapot_ex00.mi ... LINK 0.0  error  191007: cannot load 3dsmaxhair.dll, The specified module could not be found. ... LINK 0.0  error  191007: cannot load mayabase.dll, The specified module could not be found. ... LINK 0.0  err

How to export mi file from 3dsmax. 1. Assign mental ray renderer as Production renderer First open the Render Set Up dialog. Figure export_mi_1 show that opening the rollout of assign renderer and then choosing the mental ray renderer as Production renderer. Figure export_mi_1 2. Export a mi file from 3dmax. Choose Render Set Up --- Processing Tab. First you need to choose a filename as in Figure export_mi_2. Without a file name, the checkbox of 'Export on Render' is disabled. This was difficult for me. I wanted to export a file, but Export on Render is disabled. I wish I could choose the Export on Render and then see a warning message, ''an export file name is not specified.'' Next, push the Render button, then a mi file is exported. Figure export_mi_2 This is also difficult for me. When you ' export ' a file, push the ' render ' button. I wish it was like   When you ' export ' a file, push the ' export '

Even iray has no customized shaders, iray has a shader. It is mia_material (Arch&Design in 3dsmax) only. Actually, it is a shader that has mia_material interface and the implementation is different from mental ray (only for iray). mental images explains this is for the users who already know the mia_material. Such user doesn't need to learn the iray shader from the scratch. Therefore, some of the physically meaningless parameters of mia_material are disabled. They also said that they will support more physical shaders, like BRDF shaders. Someone  asked about volume shaders support at the confenence, but, unfortunately, iray version 1 doesn't support volume shaders and will be supported in the following versions sometime. As for a DCC software user, the problem of iray is they can use it from 3dsmax/Maya/XSI or not. But NVidia's explanation is 'that is autodesk's decision.' Although, mental ray 3.8+ standalone or NVidia RealityServer support iray. (See ment