GI cache question

[Thejazzshadow]

So I am making a large render by combining a bunch of crops. I was going to make gi cache files for each of the cropped areas and combine them after. When numbering  the caches, does it matter which order I render the caches in (left to right, up and down)? thanks

[rcallicotte]

I don't know, because I haven't done it, but logically speaking it might matter.  But, I wouldn't know for sure.

[Tangled-Universe]

Doesn't sound like a logical workflow to me.

I would calculate/write a single GI cache for the whole render, so no crop.
Then select an area to crop render and in the GI settings specify the GI cache file for the whole render.
Perform crop render.
A single GI cache for the entire render would give seamlessly rendered crops.

Obviously you're probably doing crop renders for RAM usage reasons, so the above may not even apply at all.

So to get back to your workflow/idea:

It wouldn't make a difference to generate a GI cache of a crop first and then render that same crop with that GI cache.
It's the same as rendering a crop without using a GI cache file.

To avoid seems in crops you either must have a GI cache for the whole render (ideal) or use accurate GI settings, maybe with some pre-padding for geometry and GI.

[Oshyan]

There are actually 2 ways to go about this. You can either do as T-U says, generate 1 GI cache file for the full image and use that for all crop renders. This can be done either at full resolution, if your system/render time budget can handle it, or at a lower resolution/detail, i.e. you can have a 1000x800 GI cache applying to a 4000x3200 image, just keep the image aspect ratio the same. A GI cache file at lower resolution than your main render will of course result in lower GI detail, similar to just turning down the GI relative detail.

OR you can actually render GI cache files for each crop region (presumably at full resolution), making sure to number them sequentially, then use "equal blend within range" and set the number of blended files equal to the number of crop regions/GI cache files. This too will work, and *may* be a way for you to get maximum GI detail if your system can't handle doing a full resolution uncropped GI calc. It's more complicated/laborious to do it this way, but it does work. Numbering order should not matter since the renderer basically combines all GI files into a single GI data array at render time.

- Oshyan

[Tangled-Universe]

Question remains then if the system still can handle the x number of blended GI caches in its memory?
If you do this to save memory then it probably is still the most feasible to render crops with GI and not using caches at all.
Or indeed, use a lower resolution cache.

[Oshyan]

Yes, it could still be a memory issue. It's useful for distributing large renders across multiple machines though.

Rendering crops with GI and no cache will result in seam issues. So the only alternative, if memory is an issue, is lower resolution GI cache with higher resolution final image. This works pretty well in my experience.

- Oshyan

[Thejazzshadow]

thank you everyone. That answered my question.

[Tangled-Universe]

thank you everyone. That answered my question.

But not ours/mine

Do you use crops because of RAM or only to split rendertimes? And consequently, which approach of the suggested ones did you choose then?

This information might be useful for others, so that's why I'm asking.

[Thejazzshadow]

Oh sry Tangled. I forgot to go back and answer that. I am doing crops because of ram issues. I decided to go with the one large cache file and crop render the final passes. Thankfully this ended up using the right amount of ram. I might need to resort to the method of splitting cache files or just splitting the render if I get bigger than this though.

[Tangled-Universe]

Thanks, no problem