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valanchan
07-14-2017, 08:00 PM
Hi,
I'm redoing an old scene.'
The renders should be around 25 Sec each. I left it rendering and came back a few hours later and each frame had jumped to several minutes.
I rendered a few frames to check and they jumped back to about 25 Sec, but the rendering time would increase if they were in a sequence of renders.

Anyone know why?

My MacBook Pro
13" 2016, 16GB,
Connected to power.

Sensei
07-14-2017, 11:31 PM
If any kind of cache is enabled, interpolated cache,
it's growing, and growing, and growing..
Cache takes memory,
and the more memory to analyze while reading cache,
the slower it takes.
Especially troublesome if animated GI cache is enabled.

Scazzino
07-15-2017, 10:34 PM
One trick I've used to help reduce the time it takes to render a scene with the interpolated animated cache is to break it into two segments, each with their own cache. I render one segment forward and the other backward and let them overlap by a second or so. That way each cache only has to grow half as much as if I rendered the whole scene so they only slow down half as much. You can do this with more segments if necessary and just let them overlap between segments. Then you can blend the segments together in post using the overlapped frames so that the radiosity calculation difference is hidden.

daforum
07-16-2017, 12:52 AM
One trick I've used to help reduce the time it takes to render a scene with the interpolated animated cache is to break it into two segments, each with their own cache. I render one segment forward and the other backward and let them overlap by a second or so. That way each cache only has to grow half as much as if I rendered the whole scene so they only slow down half as much. You can do this with more segments if necessary and just let them overlap between segments. Then you can blend the segments together in post using the overlapped frames so that the radiosity calculation difference is hidden.

Cool trick Scazzino.
Just out of curiosity, how do you render backwards? (I've never done it)

Sensei
07-16-2017, 12:57 AM
Set Start Frame > End Frame, and Step Frame -1.

daforum
07-16-2017, 10:34 AM
Ooo that's clever. Thank you Sensei :thumbsup:

So for example: [1 - 99, FrameStep 1] would be [99 - 1, FrameStep -1]

valanchan
07-16-2017, 08:53 PM
Thanks for all the replies and suggestions.

I've only just got s machine that makes animated GI over a long scene plausible.

What about baking the GI?

Sensei
07-17-2017, 04:58 AM
Animated GI cache must be baked, then Locked.

sk810
07-18-2017, 05:34 PM
Another way to speed it up is to render without motion blur. But render using "Composite Buffer Export" and do the motion blur in Fusion. I need to do a tutorial on this.

daforum
07-28-2017, 12:23 AM
Ooo that's clever. Thank you Sensei :thumbsup:

So for example: [1 - 99, FrameStep 1] would be [99 - 1, FrameStep -1]

Just out of curiosity was this right? Or should it be "frame 1 - frame 99, FrameStep -1" ?

lertola2
07-28-2017, 06:03 AM
Yes, start frame 99, end frame 1, step -1

daforum
07-28-2017, 08:49 AM
Thanks lertola2 :thumbsup: just have to watch out for motion blur looking wrong i suppose.
( sorry posters i didn't mean to take over this thread!! )

Scazzino
07-31-2017, 10:34 AM
The order of rendering shouldn't affect the motion blur, each frame is rendered independently AFAIK. Sometimes I've broken up a long animated radiosity cache scene into four segments, each with a slight overlap (and its own radiosity cache) and then blend them together in comp to hide where they meet. That way each radiosity cache only covers 1/4 of the total frames so it doesn't bog down the rendering as much as if it were allowed to cover the entire animation. You don't need to render any of them backwards, I just do that sometimes if different machines are different speeds and I'm not sure where they will actually meet. Then the faster machine can render more frames than the slower one without wasting any time.

daforum
08-01-2017, 08:45 AM
Thanks for the info Scazzino.

I was just fascinated about how to render backwards (and was curious if the Motion Blur would render backwards too??)
Guess that's why a lot of posters to this thread have suggested rendering without MB then doing it in Post.

Danner
08-01-2017, 09:47 AM
MB works in reverse too. People are recommending it to be done in post because it's a very time consuming pass and doing it in post gives you extra flexibility.

Scazzino
08-01-2017, 11:44 AM
Same with DOF. It's slow to render and once rendered you can't change it. So I tend to just use a little in camera DOF as a minimum and also generate a depth pass. That way I can apply a further boost to the DOF and smooth out some of the DOF noise in post rather than in camera. That gives me the best of both worlds.