Banding when Crop Rendering

[PeanutMocha]

I have a scene that will take a few days to render on one PC.  To speed things along, I am rendering on multiple PCs using the Crop feature, from the command line, like this:

"%TERRAGEN_PATH%/tgdcli" -p WestwoodZoomSunset.tgd -hide -exit -r -tiley %1 %2 -o WestwoodZoomSunset_%1_%2.bmp

%1 is something like 0 and %2 is something like 0.1

When assembling some partial renders, I notice very distinctive banding in cloud layers that are backlit by a sunset.  How can I prevent banding?

[attachimg=1]

[Tangled-Universe]

Those are seams caused by differences in GI calculations between the crops.
There are tons of topics about this around here which will offer multiple suggestions.

Current best solution is to have the GI cache generated separately and have all the machines use that GI cache.
To do this go to your render settings and choose the GI settings.
There select write GI cache and give a name and place to store it.
Render the complete image (NO CROP!) with that single machine. It won't render the image, it will only calculate the GI and save it to a cache file.
This file holds the complete lighting computation of your frame.

Then load the same tgd into your machines and go to the GI settings again.
Now choose "read GI cache file(s)" and select the previously generated GI cache.
The mode needs to be set to "one file (exact filename)".

This way every instance of TG2 you're running on your machines will use the same lighting solution for rendering and there won't be any seams anymore.
The reason there aren't seams on the ground is that there's barely GI going on there.

Cheers,
Martin

[PeanutMocha]

Thanks, I'm trying that now.

I assume that the pre-pass is the GI pass?

[Tangled-Universe]

Thanks, I'm trying that now.

I assume that the pre-pass is the GI pass?

Yes it is

[PeanutMocha]

6 hrs on an i7 and the pre pass is only 25% done :-(

[Tangled-Universe]

That sounds like you're either rendering a HUGE image or using insane rendersettings, or both

What resolution are you rendering and what are the settings of your render?
I'd like to know detail setting, AA settings and if you're using RTA then also the cloud sample numbers and what quality number those samples give.

[Tangled-Universe]

My concern is, that as your pre-pass already takes so long to finish, that the cache output will be many GB's.
Loading that cache into RAM of each of your rendernode may be too much already.

That's why I was asking about resolution and all the settings.

Doing things like these require sensible planning, but so does rendering with TG2 in general or one should do at least.