Mental Ray Speed


Hi all,

I’m doing a moving image project with quite a lot of frames ( 2 min video at 30fps )
Each frame takes 23 mins to render ( I use GI + FG, with the same photon map and the FGmap set to “Freeze”, so it doesn’t flicker ) All works fine, but I just wonder if you know any tricks to speed up the rendering … even with 2 PC P4 2.4Ghz it’s going to take me a while …

I’m rendering from Maya, but would it be faster via the command line ?

Any trick welcome…

Thanks !


23 mins / frame doesn’t sound that bad. Of course it depends on your scene/shaders/resolution/etc.
If you need to speed things up you should look into your sampling settings, your BSP tree settings as well as your raytracing depth settings. Area light sampling also has a big influence on render times - you might wanna look into that also.


The video size is pretty normal ( PAL square pix 768x576 ). The time per frame could be worse, but at 23mins/frame that mean I probably have to leave my 2 computers running for 2 or 3 weeks … it’s a bit much …

Thanks for the suggestions Chris-TC, I am using 1 Area light, so I’m going to check the sampling … nothing in the scene is transparent, so I put the raytracing depths to 1 ( I use reflections on all pretty much all materials :slight_smile:

Could you tell me more about the BSP tree settings ? I have no idea how to configure that monster …

Thanks again :slight_smile:


What u probably need is to go over optimization… :wise:
Our good friend Paolo Berto wrote this paper.

Chapter #4 - Memory optimization guideline
[li]understanding mental ray cache manager [/li][list]
[li]dynamic job execution [/li][li]geometry cache hub[/li]

[li]Collecting informations [/li][ul]
[li]getting and reading rendering messages [/li][li]know your system memory limits [/li][li]set mental ray memory limits[/li]

[li]optimize memory options [/li][ul]
[li]use Maya 6 “Render” command to render .ma and .mb files [/li][li]export to .mi and render with ‘ray’ [/li][li]memory map [/li][li]floating point textures[/li]
[li]Triangle Export of Polygon Meshes [/li][li]render as less frame buffers as possible [/li][li]Choose acceleration algorithm, tune BSP [/li][li]use raytraced shadows, shadows BSP [/li][li]load objects on demand [/li][li]rapid motion blur [/li][li]incremental changes on multiple frames [/li][li]approximations [/li][li]trace flags & multiple approximations [/li][li]multipass rendering Vs rendering separate layers [/li][li]FG falloff [/li][li]Number of objects and size [/li][li]Shading networks[/li][/ul]
[/list]Here is the link. ENJOY =)


great link Julian!!! very nice docs there that I’m going to be reading through. Gave it a quick glance, but it looks great. thanks


depending on the scene, you could try layer rendering.


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