I’ve read other threads about similar issues, but none that seem to exactly match mine.

Using a daylight system (default settings).
Scene has about 400,000 polygons.
Final Gather (draft)
No GI
Mostly A&D materials.
Render Elements = unchecked
A few “conform” modifiers, edit poly, and UVW unwraps

At some point the scene rendering times went through the roof, but I haven’t been able to track down what has changed in the scene to cause it.  I suspect there is a mental ray bug relating to a particular material type, object modifier, or something, that makes it go nuts.  I just don’t know what it is!

I’m distributing rendering between 3 machines, and the CPU’s are at 100% during rendering.  Computing final gather points takes FOREVER, and so does the rendering.

I’ve done a lot of scenes like this, and many with 4 times the poly’s, but this one just seems broken.  I expect the rendering to take 3-5 minutes, but it takes an hour or more.

Oh yeah, where are my shadows?  I hate 3DS sometimes.

Thanks for any ideas!  BTW, is there master list of known mental ray issues in 3DS?

Do you have any standard materials applied to objects in this scene?

Sure do!
Even when I use the material override, the rendering time seems exactly the same (ie. absurdly slow).

I have overcome, rather than solved, this issue.

I “save selected” all of the important geometry in the scene, reset Max, merged the selected geometry, remade a fresh daylight system, and everything is working as expected.

Hi,

Was it slow prior to starting actually doing the FG pass, or during the FG pass, or during the render pass?

If it hung in the pre-processing phase, then it could have been an issue with the geometry, as you found, or an XRef or map that could not be found.

One additional thing that doing the merge does is clear the material editor along with the render settings, so that may have been the source of the issue.  I’ve had issues over the years, and sometimes things just break and I never find what the problem was.  Then I merge the scene into a new one!  :)

- Jenni

Author of "Mastering mental ray":  http://www.mastering-mentalray.com
4D Artists, Inc.:  http://www.4da-inc.com
Predisent, Chicago 3ds Max User's Group

Max Design 2013; Win 7x64 12gb i7 Dual GTX 580; Win 7x64 Intel i7…

I had a similar situation recently with a 3 mil poly scene. I was rendering with MR and FG on draft setting. Most materials are standard with only a few A&Ds.

The lighting is done with a Daylight system, no exposure control but I also have direct light with raytraced shadows and a volume light effect assigned to it.

This scene had been bugging me for days and I read every imaginable thread on the subject but nothing worked. I tried assigned a plain grey material to everything, killed the volume light, killed all shadows etc but no change.

I even tried to do my FG map at very small res but it would never finish. I tried to render isolated object to narrow down the problem and could render fine so I then checked my object count and had 760 objects in the scene (most were instances though).

What I did is attached all the objects with the same materials together to reduce the object. I now have 517 objects in the scene. I have done NO other changes to the scene than attach similar objects together. Now my FG map take 3 minutes and the overall render take about 30 min at 1280 x 720 res with 1 over 16 samples.

MR must have an object limit as it is the exact same scene with all the same settings but a smaller object count but it created a major speed improvements from over 3 hours to generate the FG map only to 33 minutes for the whole thing!

So my problem is solved but I figured I’d post this for all those with the similar problems.

3ds Max 2012, Win 7 Pro 64.
NVidia Quadro 5000
2X 6 Core Intel Xeon5650 2.7GHz, 24Gb Ram