canyon and strange render bug

[FrankB]

Hi,

apparently it's canyon time again :-)

I've have begun working on a scene. What I'm showing here is really just a work in progress. Part of the reason I'm showing it now is that I have an issue with the water in the scene, and maybe one of you has an idea on how to fix it, if possible.

Image 1 (canyon6): I have tried rendering closer to the water. You'll notice that the water is black in some places
Image 2 (canyon7): I took an elevated viewpoint. The water renders fine. Anything lower than that, and the water will begin to show the black patches again.

Any ideas?

Regards;
Frank

[schmeerlap]

Sorry I can't be of help, but it's seeing faults like this that worries me about the imminent T2 release being talked of as being the final (gold) version.

John

[Seth]

what is the smallest scale displacement ? on terrain and fake stones ?
be sure there is nothing under 0.01 (i am sure you already knew it but...)

[PG]

There was a post earlier in the week about using water on displaced terrain. Something about the camera angle being linked to the angle that the lake object is to the planets surface because it's curved or something.

[Hannes]

Nevertheless a great image!

[Mohawk20]

No ideas about the water, but your textures and lighting are super realistic!

[FrankB]

No ideas about the water, but your textures and lighting are super realistic!

thanks all :-)

... but it's really just a WIP still. Interestingly, I have changed the scene by now, and never had the water render problem anymore yet. Let's cross fingers that it won't come back.

I'll keep on doodling around, let's see if I can post a more complete render later.

Cheers,
Frank

[dwilson]

The lighting is really good and i like the rock so far.

[Tangled-Universe]

Strange render bug indeed...hmmm...no idea how that's possible.

I'm looking forward to see where this one is going. Especially the second one has a realistic feeling to me.
Very nice rockstructures too

Martin

[cyphyr]

Just an idea ... try replacing the lake object with a sphere (at planet size & location) or indeed another duplicate planet either way with a water shader applied to that instead. Might get round the issue... might not.
Hope this helps in some way.
richard

[rcallicotte]

Please let us see your end result, Frank.  This looks so promising...and worthy of a cool animation.  Then, I would begin to wonder about how you would show the scale.  This is so very nice, already.

[FrankB]

it's weird - the shadow bug appears and disappears when changing the view point. It seems to also have to do with the water subsurface depth, but I can't put my finger on it.

Despite another black area on the water, here's another version of the image. not that much has changed, no, but at least now you can see a few bushes, giving the thing a little bit of scale, although I think I need another object in there to help the viewer understand the scale right.

Thanks for the nice comments so far guys.
Haven't tried the suggestion with the second planet sphere yet, cyphyr, maybe in one of the next versions.

Regards,
Frank

[efflux]

I can't make any suggestions about the problem but this is a really cool canyon. Great rock structures.

[Matt]

[EDIT] Ah, it's in the area that's already in shadow. I think it's because the water is essentially casting a GI shadow.. any GI rays which are cast from significantly below the surface hit the water surface instead of the rest of the scene. This means the underwater surface is not illuminated by the environment.  You might be able to fix this by disabling "visible to other rays" on the water object.

(There is always a region very close to the surface where rays are able to pass through, because of simplifications and ray bias in the renderer. Also, because the GI cache is blurred, some parts close to the surface use interpolated values from the surface itself.)

Matt

[FrankB]

Great Matt, thank you. Making it invisble to other rays did the trick: the dark patch is gone. Do you think this should always be disabled in scenes where water is rather shallow, and GI is pretty much the only lightsource hitting the lake object?

Cheers,
Frank

[EDIT] I am sorry to have to revise my earlier statement :-) ... disabling visibility to other rays *helped*, but didn't make it go away entirely. The dark areas are growing again as soon as I move camera down more. Any other idea?