Tips on how to render complex scenes

[Crayox13]

Hi guys,
Now this isn't a really big scene really, just one city block. I have several different trees - vrayproxy instanced, few surfaces with pebbles, and few with grass on them both Multiscatter.
I'm attaching the scene so you see what it looks like roughly.

I wanted to render just grass, pebbles and trees (everything else is matte with alpha -1), and then buildings in another inverted pass.
For grass, trees etc. I only use IR with low setting, and no secondary bounce, but this time, I couldn't render even one view (1200x600). I put dynamic memory limit 6000Mb. Usually this way of rendering scenes like that works for me, but not this time. Multiscatter grass has 1 million limit, and pebbles are 500 000...again, a lot, but it worked on other scenes.

I also saw a vray warning now saying Performance loss:dynamic memory limit too low.

Any advices on top of your head?

[Morne]

Well how much ram does your pc have? Take whatever ram you have and deduct about 2gb from that (for windows and the other odd small thing that may be running) You could even try 1.5 gb instead of 2, but 2 safer.

So if you have 16gb, set your dynamic ram to 14gb

The scene doesnt seem that heavy, but you can try switching off max frame buffer, enabling vray frame buffer and set it to "preview mode" only. This leaves more free ram so you have more during rendering
Set VFB to save out to and EXR or VRIMG file.

Let us know how you get on

[Crayox13]

I have 8GB of ram. That's why I set the limit to 6....but I think it might be better to increase it, even tough vray might use virtual memory (which it uses anyway) because it should be faster than limiting vrays algorithms and have it unload geometry which always takes ages. What does Vlado think?

Also, I think I found a problematic vray proxy tree that was way too big...I generated it using Ivygen (so cool free little software for ivy generation).

About frame buffers...so you mean turn off "render frame window" under common tab? If I enable VFB, doesn't that automatically turn off MAX frame buffer?
What do you mean to set VFB to preview only?
thanks

[Morne]

Yes turn of "Rendered Frame Window" under common tab. Then under common tab set size to something rediculously small like maybe 12 X 9 pixels.
In the past, even though you switch on VFB and it doesnt actually show the max buffer, the max buffer still uses ram in the background. I don't know if it is still like that, but It's just a habit I adopted from the times before it was common for people to have 8GB ram and more.
So yes switch on VFB and from here put in your size. Untick "Render to memory frame buffer" and under VRay raw image file tick "Render to V-Ray raw image file" and next to that tick "Generate preview"
Remember to add a file where it will actually save the render, this can be either vrimg or exr file.
Now when you render you'll see you get a "preview" frame buffer and you can't zoom in or out from it, also it doesnt show your elements. Also it may appear darker. Don't worry this is how preview mode works. Your file will save fine.

Another thing you can do is under Settings tab set your bucket size to 32 or 24 or even 16. You'll have to experiment to see what works for you.

Let us know your results

A note on file type:
if you save to exr, all your elements will be saved in this file. You may need ProEXR plugin to read all the elements in photoshop.
if you save to vrimg same story except you can manually extract each element using the command line tool that comes with max (vrimg2exr)
OR
use this handy little script:
http://www.chaosgroup.com/forums/vbu...ight=shimakaze

[Neilg]

How are your pebble/grass surfaces done, is it one big object covering the whole scene?
Break them up into separate ones for each camera and only render the closest one. camera culling/whatever it's called may help too.

That scene really shouldn't be trouble to render, i'd say there's one thing causing you major issues. Do an grey override version, try with no gi, switch scatters off etc. narrow it down.

[Crayox13]

Thank you Morne for that detailed explanation! I'll try this buffer thing. Usually I just save elements in separate files and compose...I know about these scripts etc, but just didn't bother with them until now.

Cubicle....often I want to optimize my scenes like that but always some distant object is visible, so I just render everything lol....but luckily in this scene that one object was causing issues.

[svetlozar.draganov]

Please follow Morne advices - if you still have issue with rendering your scene , you can try to tweak Max tree depth , and Face/level coef in System Rollout.
If you decrease Max tree depth - Vray will use less amount of memory
If you increase Face/Level coef - Vray will use less amount of memory

Please take this step only in a last resort - changing these settings in to recommended at all - but in extreme cases when you have used all optimizing tricks and you still have issue you can try this one

[windowlicker]

Just a thought: Get more RAM.
As an example: 24GB DDR3 kit for around 150€ (swedish web store). And you can of course get less than that, and just add more to the RAM you have.. (and I think Swedish prices aren't the lowest, 25%VAT and all. :S) If you do this professionally, I think it's probably the best investment you can do atm.

[Crayox13]

Thanks svetlozar, will keep that in mind.
Lol...I would get RAM if I could, I use DDR1 on my old workstation with 2 Opteron 275...it's a great system still but hard to find DDR1 ecc+reg that it needs.

[chriserskine]

are you using lightcache?

mulitscatter with that uses up a lot of ram.

also I've found forestpro to be a lot more reliable when you get into bigger scenes.

[Crayox13]

Usually I render grass and trees separately without LC, but after certain update of MS (few months ago) it seams it stopped using so much memory when using LC.