Controlling processing in Render Settings

- [Instructor] Let's adjust a few key render settings to control, among other things, how Arnold uses the computer's processing power. Open up the render settings dialog. We can get to that through the menus. In the menu sets, choose rendering. In the render menu, render settings. And there's also an icon on the status line up here. It's a clapboard that has a little gear on it, display render settings.

Let's go over to the system tab. And we start off with the Maya integration section. The most common switch you'll want to throw here is progressive refinement. This gives an immediate low-fidelity preview of the entire frame. The finished high-fidelity tiles of the rendering are called buckets. The progressive refinement switch determines whether or not the low-fidelity preview is calculated before the finished buckets.

If we turn this switch off, then production renders will be a little faster because the preview isn't being calculated. In the render settings section down here, we see some more options. By far the most important one is auto detect threads. It controls Arnold's processor usage. It's on by default and when it's on, Arnold uses 100% of the computer's processing power. I recommend throttling that down, leaving some processing headroom for other applications and avoiding potential problems such as the render crashing or the computer overheating.

If we turn auto detect threads off, then we can manually set the number of processor threads that Arnold will create during a production render. I've got 8 virtual cores on my computer. To leave 1/8th of processing power available for other applications, I can set threads to a value of 7. Even better, we can set this to a negative number. We don't even need to know how many cores we've got. With a value of -1, Arnold will use the available number of cores minus 1.

One other tweaky little setting, go into the Arnold renderer tab and scroll down near the bottom to lights, open that up. And there is a low light threshold attribute. If you have extreme low light conditions in your shot, then the lighting may get cropped off and you'll see black areas in your rendering. This is an optimization so that really dark areas in the scene don't get calculated. But if you do have a low light scene such as one that uses interior photometrics, then the low-light threshold cropping may be a problem and parts of your scene won't render.

If you do see black areas in the image, I recommend setting the low-light threshold to a value of 0. It's important to know that all of these settings are saved in the scene file and not in the Maya user preferences. Those are a few of the most important render settings for Arnold.