Saturday, April 28, 2012

How to save a final gather map file for each frame

When you use the final gathering for animation, you'd probably have to refresh final gather map and rebuild it from scratch at every frame unless it's a camera fly-thru only animation.
In that case, you'd have to use very high settings for the final gathering and each frame would take a good amount of rendering time. What if you have re-render the entire sequence for some reason.
All the final gather maps that you previously calculated has been over-written and only the final gather map for the last frame remains. What a waste.
So, I'll show you a simple way to save all the final gather maps that are created during the rendering.

You can access and control the final gather map's name by the attribute called

You can simply set this attribute to a file name of your choice using setAttr command like below.
The filename goes between the parenthesis. 

setAttr -type "string" miDefaultOptions.finalGatherFilename ("FGmap_save."+`currentTime -q`+".fgmap");

Here, my scene file name is" FGmap_save.mb", so I typed "FGmap_save.".
You can use your scene file name or any name.
Each fgmap name will be unique by quoting the current frame number using `currentTime -q` command and appending that to the file name.

This one-line script goes to Pre render frame MEL slot under Render Options  in Common tab.

This mel script will be executed before every render begins at each frame.
Now you can find that for every test render,  the Primary Final Gather File name updates for the current frame.

Now render your sequence with FG rebuild option ON and your FGmaps will be saved for each and every frame. 

When you need to re-render any frames or the entire sequence, just switch the Rebuild option to Freeze and render again. The renderer will locate the corresponding saved FGmap for each frame.

This can be a big time saver especially when you find that you need to adjust the Point Interpolation attribute only after the sequence is once rendered.

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