Studio Workshop - Final Gather Maps

Studio Workshop - Final Gather Maps

Ladies and gents, welcome to another Studios Assistant blog. Today's topic: Final Gather Maps.

I'm going to assume you know what Final Gather is (referred to as FG from now on), because you're all intelligent people and you know what you’re doing. I can't explain it properly in a short blog post, so what we've done for you is to split this session into two parts. Firstly, I'm going to talk you through FG Maps and on Monday I am going to help you create one. So be prepared and do a little bit of homework over the weekend…

 A problem I'm sure we've all had with FG is rendering out our project, putting it into Nuke and seeing the dreaded final gather flicker! Flicker occurs when Maya creates a burst of FG points every frame at render time. Since the points are random each time, they don't always match up, so as points appear and disappear across the surface of your scene you'll get a flickering. Most of the time FG flicker can be avoided by creating a FG map. A FG map is a file that stores the positions of FG points, forcing Maya to use these remembered points every frame, therefore eliminating flicker. 

What's great about FG maps is that they actually lower render times, which is another thing we strive towards. So there's really no reason not to bake one if you're using FG.

Now creating a FG map is actually rather easy, but it does mean that I'm going to have to try and explain one of the most ridiculous parts of Maya; the FG Rebuild settings. The Rebuild settings may start of confusing but rest assured; it still won't make sense even after you've learnt what's going on. 

In your Render Settings, once you've selected Mental Ray you'll be able to select the 'Indirect lighting' tab, which has a mini menu named 'Final Gathering Map'. In this menu you'll see the first drop-down menu is named 'Rebuild'. This has 3 options; On, Off and Freeze.

'On' means that Maya is going to create brand new FG points every frame - this is why you get flickering. 'Off' means that Maya will keep the points it creates every frame, building more points the longer your shot is. This is the option we use to create a FG map. 'Freeze' means that Maya won’t make any FG points at all, but use the FG map you've created. They're not the clearest of names, but get used to them. 

Right are we all up to speed? Any questions? No? If you want to get a jump start take a look at this video in preparation for part two... I did warn you there would be homework! See you again on Monday when we will start to make a map. So study up and have a great weekend!

0 Comments Ash Miles

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Ash Miles
Fri 18 May 2012: 11:00am

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