View Full Version : speeding up Mental Ray

07 July 2004, 12:38 PM
I realized that no all people in the forums have superb machines and even they have fast ones, speed is a very important thing when you have to render in Mental Ray.
Sometimes, for testing, sometimes for production.
So, I decided to start this thread to mental ray users to put advices and tips for improve render times, for testing and for production.
I wanna hear (I mean read...) you guys!

These are mine:
For testing:
-Global Illumination: reducing the GI photons will improve the Photon Emission time.
-Global Illumination: according to the scene scale, using a different size for photons (frequently bigger) will improve the render time, and the lighting overall look, if we aren't using FGathering yet (for testing).
-Antialiasing values of 1/4 or 1/16 will give extra speed in the render time, mainly when you have to get an overall look of your scene lighting.

I'll search for more...

07 July 2004, 03:16 PM
I think there is a thread in the resources section that does just this. :)

But here goes:

1) Make sure "Max Displace" and "Displace Length" are the same value. Or else you'll get crappy displacement and render alot slower too.

2) Before raising the Max settings, try lowering the contrast values in the spatial settings to see if that improves the quality of the image. Also enabling "jitter" helps with flickering in animations. But like fabbrizzzio said, for tests just lower the max settings to 1/4.

3) Mental Ray Shadow map is your friend. :-) Saves alot of time if you just want soft shadows without using area shadows. It's better than max's shadow maps for sure.

There is a site that had a link to a softimage/mental ray optimization PDF. If anybody has a link to that site that would be good.

07 July 2004, 12:38 PM
- To increase the GI lighting in the scene without increasing photons number, use a big sphere with normals flipped. This way photons are not going to loss in space (they're gonna bounce in the sphere and will be back in the model, generating more photon impacts). This works fine in outdoor scenes. :thumbsup:

07 July 2004, 11:23 AM
Well it seems that no one is contributing, it might be that there are already a few "let's research mental ray" threads. But I think this could work....since it's just putting every techinque together in one little FAQ :-)

1) If you have more than a gig of ram, well also depending on scene size(try 500,000+ triangles), try increasing the BSP depth and decreasing the BSP size. It can help render a bit faster. Using Large BSP can help also for big scenes.

Infinite Vacuum
08 August 2004, 07:46 AM
Not sure where i read it, but it seems to optimize a bit the leaks of memory of mental ray. You need to edit your boot.ini file. It should be on c: (root). It is flagged as system file and hidden file, so you need to type " C:\>Attrib boot.ini -s -h -r " in order to be able to edit it.
After editing it, save it and do the attrib thing again, but instead the "-", use "+".

My file looks like this one:

[boot loader]
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional"/fastdetect
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional -PAE-" /fastdetect/PAE/3GB

The last line is what you need to write. This will create a starting menu where you will have two options for initialize windows. I did this that way because i was not very sure of doing those tweaks. If you experience problems, simply select the first option in your next boot and you will have your old configuration.

Oh, another litte trick. 3dsmaxcmd (render from commandline) is very good for speed renderings. Since you can tweak parameters from the console, it can save you some time.

Hope that helps!

08 August 2004, 09:55 PM
When you reach the desirable amount of photons GI or Caustic, save your maps.

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