Faster rendering with mental ray?

[Ardak]

Hi, I'm doing a landscape sequence with lots of vegetation. For the ground I use three layers of plants taken from Vue 8 xStream library, and few trees here and there. The problem is that rendering time is pretty massive, considering that I have to render out sequence 620 frames long. I am using proxies for all of the plants, and Forest Pack Pro as scattering plugin.

 

 

Rendering settings for this image are:

 

Antialiasing

Medium: Min 1/4, Max 4

 

Soft Shadows Precision:

0.25X - Low

 

Final Gather Disabled

 

Glossy Reflections off

 

Glossy Refractions off

 

Filter Type: Box

 

Spatial Contrast

R: 0,051, G0,051, B: 0,051, A: 0,05

 

Lock Samples: On

Jitter: On

 

And resolution of 1280x720

 

Computer Specs:

 

Intel Q8300 @ 2,50GHz

8 GB DDR2 800Mhz RAM

GeForce 8800GTS

 

And rendering time for one frame: 54 minutes. A bit too long?

 

Any help would be greatly appreciated. Thank you very much

[Justin Hunt]

What is your lighting setup?

 

jhv

[Ardak]

One Omni Light with mental ray shadow map. Shadow map size 4000 and samples 32.

[Justin Hunt]

Shadow maps and Omnis are very in-efficient and slow to render.

 

Rather use a directional light with ray-traced shadows.

 

Also turning the opacity map (on the leaves/ trees) sampling to "None" will help speed things up a bit.

 

jhv

[Ardak]

Thanks Justin. I will look into these settings.

[Ardak]

Hmm, it seems that the rendering times weren't improved drastically by using Directional Light and Ray Traced Shadows. I checked the opacity maps and they were set to None, and I even lowered the polygon counts from the plants pretty much. I should be able to use atleast Medium antialiasing preset, because if I go lower, flickering is introduced. Any suggestions?

[odouble]

I see you are using Forest and Mentalray. I'm currently working on 5 scenes that have over 100,000 tree/plant instances in each scene viewport at any given time. The itoo website says there are issues with the plugin and Mentalray's memory management when you get over 500,000 instances or proxies. It has no such issues with Vray.

Here's the link to itoo's technical notes:

http://www.itoosoft.com/forestpack/reference/rendering.php

 

When I started this project, I went the road of vue and carbonscatter but settled on our geometry tree/plant library. The issues with vue trees in Forest was the opacity maps in the leaves. You can turn off the filtering or even use them in the reflection slot with a 1.0 ior trick but they still don't render as fast as full geometry trees and with geometry leaves that have no opacity maps. I also converted all my trees to proxies before scattering with Forest.

 

Another thing that helped was using the camera clipping distance and density falloff parameter in the Forest plugin under the camera tab. I couldn't render my scenes without breaking them into passes for each forest object before but they render in one beauty pass now in about 25 mins at 3k. I find that adjusting the aliasing even to 16/64 does not crash max. My original issues seemed to stem more from opacity maps and Mentalray's memory limitations with tons of instances(even proxies). A good thing to do is have your Render message window open to see where your bottleneck is.

[Ardak]

Hi odouble, thanks for your advice. I decided to try another scattering plugin, since Forest and mental ray doesn't go well together, and all in all Forest is quite buggy. Does mental ray have memory issues using another scattereres, or is it only with Forest?

 

And when you said this "I also converted all my trees to proxies before scattering with Forest.", have you then rendered successfully scenes with no proxy-plants at all, just models?

 

"...But settled on our geometry tree/plant library." What you use for scattering when you use your own asset library?

 

Thank you for your time

[odouble]

From my experience, the limitation seems to be with Mentalray and how it handles memory and not with Forest. It might also just be the 3ds max incarnation of Mentalray... can't really speak for other packages.

 

I used another popular scatter plugin that was originally made for Vray, but Forest seemed to be much more optimized for Mentalray (I did think the other plugin was more intuitve to use though).

 

As for the reason I used proxies... The file size started to become an issue and that affects load times over the network with backburner. I never could render the scenes with pure mesh geometry also. The proxies just make me sleep better too...Huge difference in the file size.

 

I have settled on Forest for this project because it's doing what i want. that is not to say that there aren't other solutions that work.

 

A really good thing to do if all else fails is to separate your Forest scatter elements into as many differerent entities as possible. For example I have a Conifer Forest scatter that's separate from the ground shrubs(multiple scatters), deciduous trees, rocks etc. I have about 7-12 Forests scatter elements in each scene. It makes it easier to control and more straight forward to render out in passes to save memory and time. I use the "render subset of scene/masking" in the camera shaders lens slot to render out each pass. You can also just use the matte/shadow/reflection material or separate matte render elements using pre-assigned selection sets for each Forest.

 

Hope it helps.

[Justin Hunt]

Be sure to use BSB2, Scanline OFF and "use Placeholder objects" ON, This way the proxies and other objects will load and unload on demand. You should be fine with the 8gig's of RAM.

 

I havn't used Forest PRO so I can comment on it. I find the object painter in Max does the job for me. I have successfully rendered 100's of trees and plants with only 4gig RAM.

 

jhv

[Ardak]

I will look into these settings. What lights should I use with VRay? I found it hard to generate good shadows on the scene with it. Thanks.

[Justin Hunt]

I am assuming that you have switched to Vray, then just use a vray sun. If your still using mental then you cant use vray lights.

 

jhv

[Ardak]

Okey, so I tried to render one layer of vegetation, I used VRay proxies of quite lowpoly plants, VRay Sun as light, and basic rendering settings, and it takes 1h and 22min to render it. I really doubt that my computer is only capable of rendering scene with billboard models in efficient time.

[Ardak]

What would be good settings considering video rendering with VRay? Thanks.