Lighting going nuts from frame to frame during animation

[rca06d]

At around 10 seconds in this animation, my lighting starts going nuts and randomly changing color and brightness like every other frame. I can go to a frame that got messed up, and render it solo and it turns out fine, it just seems to do this when I render using the sequence output panel. Any idea what's going on here?

[WAS]

Sounds like you are animating lights or planet around them. In order to do this appropriately you need to render GI cache files for your sequence. You than need to load them back into GI cache file loader with %04d placeholder for sequence number to load the appropriate cache file corresponding to the frame. Interpolate the cache files. Maybe every few frames.

During your sunset Terragen is simulating color shifts and each GI cache render for each frame at render time can vary from the last frame, hence interpolation and finding sweet spot to blend GI cache files so those variations aren't as noticeable. 

https://planetside.co.uk/wiki/index.php?title=Terragen_4_Global_Illumination#GI_Cache_File

[rca06d]

Interesting, ok I'll look at the GI cache stuff. Why doesn't animation just work like rendering a still frame? Seems like it should just use whatever exact lighting I have for that frame.

[rca06d]

Hmm, I'm doing a little reading at the link you posted. Following the instructions for animation, I saved a cache file every 10th frame and I'm blending 4 together for a frame. Now my scene is weirdly brighter. From the docs, I don't really understand what the purpose of this pre-caching and interpolating method is. Why would I do this? Sure, to avoid a flicker, but I don't really understand the source of the flicker I think, and why the scene would render differently for a frame during animation than during still rendering.

[WAS]

Because ambient light is approximated.