View Full Version : Mental Ray Speed

04 April 2006, 10:15 AM
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 !

04 April 2006, 12:57 PM
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.

04 April 2006, 02:34 PM
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 :)

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

Thanks again :)

04 April 2006, 04:53 PM
What u probably need is to go over optimization... :wise:
Our good friend Paolo Berto wrote this paper.

Chapter #4 - Memory optimization guideline

understanding mental ray cache manager

dynamic job execution
geometry cache hub

Collecting informations

getting and reading rendering messages
know your system memory limits
set mental ray memory limits

optimize memory options

use Maya 6 "Render" command to render .ma and .mb files
export to .mi and render with 'ray'
memory map
floating point textures

Triangle Export of Polygon Meshes
render as less frame buffers as possible
Choose acceleration algorithm, tune BSP
use raytraced shadows, shadows BSP
load objects on demand
rapid motion blur
incremental changes on multiple frames
trace flags & multiple approximations
multipass rendering Vs rendering separate layers
FG falloff
Number of objects and size
Shading networks

Here is the link. ENJOY =)

04 April 2006, 06:48 PM
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

04 April 2006, 08:57 PM
depending on the scene, you could try layer rendering.

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