Unsolvable Bucket artifacts?

Started by StephB, December 09, 2018, 09:12:51 am

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StephB

Hello,
I just registered here but I'm familiar with the forum and Terragen ;)

Nevertheless I'm struggling with artifacts in clouds despite all the tests I made and the tips I found on the forum.

The situation is this one : I have a scene with three cloud layers (one 2D cirrus, high level layer, one V3 medium layer and one V3 lower layer.
Rendering through a render farm, I now always encounter bucket artifacts with high res renders. Testing with 3000x1500 for instance. Artifacts are probably linked to GI in clouds, but I tested acceleration to none, GI file sent to the farm, higher "GI in cloud" setting, padding, etc.. to no avail.

At home, I never experienced that : all renders are ok, as far as they are done in one run. I experience inconsistent GI in clouds once when rendering a large image in several parts (cropping) but solved it with a pre-generated, huge GI file.
On render farm, I experienced that once and solved it with higher GI in cloud setting (very high) and probably acceleration to "none".

But now, I'm out of solution.
Any idea?

I read here that rendering a GI pass file at lower resolution (say 1500x1000) and use this file for farm-rendering at higher resolution (say 6000x4000) would work. Is that true? If so, it will be very helpfull as I can't imagine having to upload 2GB GI file for each render on the farm.... :/
Photography & Graphic Arts
http://www.stephanebeilliard.com/site/

StephB

Attachment:
typical artifact in cloud (bucket size, square)
Photography & Graphic Arts
http://www.stephanebeilliard.com/site/

StephB

Attachment:
banding artifact I found in a farm-rendered image when using a pre-generated GI pass file.
Photography & Graphic Arts
http://www.stephanebeilliard.com/site/

Matt

I think it's probably the Cloud GI Quality. You might need to set it even higher (e.g. Sequence x4, or higher).

I'm going to provide some way to store this data in GI cache files in future versions, but at the moment the only solution is to increase quality to reduce the per-frame/tile differences.
Just because milk is white doesn't mean that clouds are made of milk.

StephB

OK Matt, I'll give it a try. Thanks.
(I thought "sequence" settings was for animation, btw)
Photography & Graphic Arts
http://www.stephanebeilliard.com/site/

Matt

It is, mostly, but the sequence settings are really just higher levels of quality than the still image settings. I wanted to use the "still" vs. "sequence" naming to steer people towards using the lower settings for still images, otherwise too many people would use much higher settings than they need, resulting in unnecessarily slow render times.

Usually it's only in animations that you need the sequence levels, to prevent flickering frames. But tiled rendering has similar quality requirements to sequences because you notice differences between tiles that you wouldn't notice when rendering the image as a whole.
Just because milk is white doesn't mean that clouds are made of milk.

StephB

Unfortunately, increasing the GI cloud settings didn't help...  :'( :(

Tried Sequence x4, x8.
Photography & Graphic Arts
http://www.stephanebeilliard.com/site/

Matt

December 10, 2018, 05:04:43 pm #7 Last Edit: December 10, 2018, 05:07:21 pm by Matt
And you're also using a pregenerated GI cache file?

Can you send us a .TGD to support@planetside.co.uk? I'd like to figure out exactly what's causing this.
Just because milk is white doesn't mean that clouds are made of milk.

StephB

December 10, 2018, 05:06:10 pm #8 Last Edit: December 10, 2018, 05:13:38 pm by StephB
Can it be caused by the cloud settings themselves?

I noticed I checked the "accelerate empty space" box but tried also without and the problem's still here.
Photography & Graphic Arts
http://www.stephanebeilliard.com/site/

Matt

It appears to be in the atmosphere, but the light in the atmosphere is affected by other things. Usual culprits are:

1) Differences in GI in atmosphere. This should be solved by the using a GI cache file.

2) Shadows from another cloud layer:

a) The voxel buffer and/or 2D shadow map can change from one frame/tile to the next, but I've rarely seen such a big difference.

b) The most common cause of differences in shadows is the Acceleration Cache, so you should always set that to "None" on every cloud layer that could cast a shadow into the scene.
Just because milk is white doesn't mean that clouds are made of milk.

StephB

Hello,
concerning my rendering issue, I got no other option than generating the image in a single -long- run on my side. Got a quite nice render that I was able to use :)
But I'm a little bit concerned for future ideas... :-\

Photography & Graphic Arts
http://www.stephanebeilliard.com/site/

Oshyan

Are you able to share the TGD file privately with us? We can try to troubleshoot the issue further here. You should not have to do a single-thread render.

Beautiful end result though!

- Oshyan

StephB

Oshyan, I actually already sent you the TGD file, following Matt's post. You did not receive it?
Photography & Graphic Arts
http://www.stephanebeilliard.com/site/

Matt

I received the file and have been working with it to try to understand the cause of the problem. So far I don't have a solution but I will keep on it.
Just because milk is white doesn't mean that clouds are made of milk.

Oshyan

Oh yes, that makes sense. Sorry, I thought it was a different file.

- Oshyan