View Full Version : Optimizing Render Times

10 October 2004, 02:31 PM
Hey, I had a quick question regarding any techniques or tricks that would allow render times to be as quick and painless as possible. I have heard that there are some good techniques out there for this.

I am aware of, and have used, multi-pass rendering before, but I was wondering if there were some software specific features that speed up rendering times that I am unaware of. I recently discovered the segment memory limit which was set to some horribly low number like 10 mb, and subsequently increased that to the maximum amount of RAM on my PC. Are there any other features such as this that I have not occasioned in any of my readings, or am I just out of luck and stuck with some insanely huge render times? Any suggestions would be much appreciated.

10 October 2004, 02:52 PM
As far as the segment memory limit is concerned, I'd suggest you try out different values. Personally, I found if you increased it much beyond the minimum necessary to do the render in one segment, it would actually slow the render down. Another big trick seems to be to get P4 processors, I made the mistake of getting AMD, which lack SESS2 (or whatever it's called). Oh, and never, ever do projects involving refraction/caustics! ;)

10 October 2004, 10:10 PM
Try dropping the ray recursion leavel down from the default 16 to something more reasonable. If your not using refraction, caustics or radiosity you can often drop it down to 2!

10 October 2004, 10:35 PM
Jaspar: Just out of curiousity, what is the minimum Ram required to render one pass?

Also, 2 additional questions:

1. If you have to use radiosity and caustics, is there anything that you can change to decrease the render time, but still get good results?

2. Is FPrime really worth it???

10 October 2004, 12:15 AM
Cyphyr: Awesome idea in regards to the ray recursion level...I wasn't sure whether or not that had a big impact on the overall look of the scene or not. I'm using sasquatch to create a jungle-like envioronment with volumetic light streaming down through the trees onto the grass which casts shadows you think reducing the ray recursion level would have an impact on the light quality (the volumetric light plays a huge role in this makes or breaks it). Do you think dropping it down to 2 would still produce sufficient image quality?

10 October 2004, 12:20 AM
Artistic Visions:

1. The minimum segment memory limit varies from scene to scene depending on each scene's individual complexity...if you're using volumetric lights, high poly characters, numerous objects, etc., the minimum segment memory limit will be higher than just redering out a single low poly character. I reccomend playing around with values untill you come across the one that works for that particular scene...try starting out around 20 megs...that's usually a high enough number even if you're rendering a D1 NTSC image.

2. My experience with FPrime is that if you have a computer with a fast enough processor and a nice video card then it's worth it...otherwise I've found it takes too long to update.

10 October 2004, 12:51 AM
try starting out around 20 megs...that's usually a high enough number even if you're rendering a D1 NTSC image.Well, for me I'm starting to render out my images for Print resolution, so that might not be high enough. Maybe 100-150 MB?

Rabid pitbull
10 October 2004, 01:12 AM
Artistic Visions:
2. My experience with FPrime is that if you have a computer with a fast enough processor and a nice video card then it's worth it...otherwise I've found it takes too long to update.
Fprime does not use the video card in processing at all. The cpu and ram do get highly demanded with it though. Of further iportance to realize it that at this time fprime does not utilize dual processors or hyperthreading.

Fprime is a amazing tool and the first time you use it your jaw hits the floor. :thumbsup:

10 October 2004, 01:21 AM
Nothing will help you more than multipass rendering. Instead of trying to render all the details of the scene, break it down into layers and composite those layers together at the end. The simpler you can make the problem that you ask the computer to solve, the better off you will be. The less work you have to re-do after making a change, the more "bang!" you get to keep out of the bucks you've already spent!

Don't overlook the fact that you are building a model in 3-D space to produce what is finally a 2-D output. Take full advantage of that. 2D manipulations like compositing are cheap and fast, but they can give you (almost) the same arrangement of pixels on the screen. ("Close 'enuff! It works for me!")

Also, whenever possible, dismiss complicated (if "correct") tools like radiosity. Forget caustics if you can... might it not be possible to dream up some kind of translucent, bright, beauty-layer and layer it on there in the right spot and get almost the right look? If so, do it! In other words, cheat! :thumbsup:

You can do amazing things in CG, like setting lights in plain sight, telling them to shine only on certain objects (even if that means shining right through something else), to cast shadows instead of light, and so-on. The CG world has a host of possibilities that don't exist in the real world. Embrace anything and everything that will let you get the picture faster.

I've learned way too much about cheating by doing production render work on a crufty old laptop that simply doesn't have the horsepower to do clever things. But it's turned out to be a very useful discipline, because it focuses my attention (out of necessity, mind you) upon what I want to see, and to strip the project down to the minimum model and the simplest approach that will give me something as output that looks like that. The models that do that are not "realistic" models; not at all. But the output that I get, is. If I can get there by fooling the eye, I will do so.

And it works. Sometimes I can get the results of what would be a six-hour render in, oh, twenty minutes and change... Sure, there's a lot of human setup-time and planning, but if the picture turns out slightly-wrong I can just adjust the right layer, type make on the command-line (yes, I use Makefiles... straight out of programming), and in a few seconds or minutes I'm looking at a repaired shot. Not "Yet Another Six Hour Render."

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