The sky is falling!! The sky is falling!!

Started by N-drju, January 02, 2015, 02:50:23 AM

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N-drju

Hi guys,

I've ran into a strange artifact lately, while I tried to make a test render of my image. Of course, ignore the barely finished state in which that render currently is and a partially covered plane in the middle. Instead, look at the sky (or rather a place where it should be!)

[attach=1]

Fortunately, I remembered what I've done right before taking this render - I added a very dense fake stones shader at the foothills, since I wanted to simulate stone and gravel deposits. The density was 0.91 while the stone scale was about 0.15. I also added a touch of small, colored displacement to the stones.

When I disabled the fake stone shader, the sky was back to normal.

What is even more interesting is that when I tried to render the same scene in full HD (cropped into half) the sky also turned out nicely. However, when I made a quick render once more the sky went cacka-cookoo again. Later I got two error messages and the image in the preview window started to pre-render without the sky. I believe that this must have something to do with the memory.

Frankly? I don't care, as apparently I can still render in normal definition. I am just surprised because I haven't experienced any memory issues in a looong time, especially due to displacement shaders!

Still, I'd like to hear your opinion. Any thoughts on that guys? And may this year be lucky and better for you than the last one was! :)
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"

Dune

This is very funny, but I wouldn't know what caused it. You didn't accidentally hook the fake stones into the sky?

WAS

Quote from: Dune on January 02, 2015, 03:53:00 AM
This is very funny, but I wouldn't know what caused it. You didn't accidentally hook the fake stones into the sky?

Lol that.

I've had weird things happen with offsets on fake stones. Like causing the land to sink in, or spikes to reach for the sky. Though not quite this. xD What sort of surface setup do you have for the fake stones? Default (no shader)?

N-drju

@ Dune:  ;D That's like using fake stones shader on human models to simulate smallpox!

@ WASasquacth: Yes, I also played with "exploding" fake stones. ;) But this... I use no surface at all with these stones! Just color. (If you look closely, you can see a slightly brighter lines near the foothills - that's them). I just added a very, very small displacement with black-and-white power fractal to mask the colors. Then, I masked the FS placement with a surface layer (you know, the one with altitude and slope restrictions?)

Generally I think that the trouble here is not the stone surface but their mind-blowing density.
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"

Hannes

As far as I know it's the fake stones shader's displacement. Do a test with disabled displacement, which should make the sky look normal. I don't remember if it's the size or the strength of the displ. function that causes these weird patterns. See? Size matters!! ;D

N-drju

Heheh. Guess what? Looks like Hannes was right with that "size matters" thingy. :P

It turned out that the troublemaker here was a power fractal shader that I plugged into FS surface shader on its own! Not its displacement!

What caused trouble was feature scale and smallest scale of the fractal pattern. I reduced them to a very small size because I wanted small stones with adequate, spotty surface. Below certain values TG was going bonkers. It's probably due to the fact that it cannot render that sort of detail from such a distance (there's about 6km from camera to the fake stones that you see in the image). These seem to be minimal values that I can apply to fake stones' surface without any side-effects:

[attach=1]

Problem solved. ;)
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"

WAS

#6
Quote from: N-drju on January 02, 2015, 11:44:50 AM
Heheh. Guess what? Looks like Hannes was right with that "size matters" thingy. :P

It turned out that the troublemaker here was a power fractal shader that I plugged into FS surface shader on its own! Not its displacement!

What caused trouble was feature scale and smallest scale of the fractal pattern. I reduced them to a very small size because I wanted small stones with adequate, spotty surface. Below certain values TG was going bonkers. It's probably due to the fact that it cannot render that sort of detail from such a distance (there's about 6km from camera to the fake stones that you see in the image). These seem to be minimal values that I can apply to fake stones' surface without any side-effects:

[attach=1]

Problem solved. ;)


There is nothing beyond 5e-007, so if you try forcing it, I can imagine how that would cause problems. Especially in relation to lead-in and smallest scales.

N-drju

Oh, there is WASasquatch. I've tried it. ;)

But it turned out that displacement played a role here too... Generally all extreme values, whether high or low are not recommended.
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"

WAS

#8
Quote from: N-drju on January 03, 2015, 08:31:19 AM
Oh, there is WASasquatch. I've tried it. ;)

But it turned out that displacement played a role here too... Generally all extreme values, whether high or low are not recommended.


Of course you can force it... but if you notice.. you can write in the amount, like 0.00000005, or 0.00000000000005 and it will convert into 5e-007 exclusively when you re-open the shader. :P So, that is the base scale TG wants you to use. Forcing it does not mean it will work... lol

I use small scales, and displacement for smooth rocks, without any sky problems. Following the base TG provides and no lower.

Matt

Quote from: WASasquatch on January 03, 2015, 05:18:18 PM
Of course you can force it... but if you notice.. you can write in the amount, like 0.00000005, or 0.00000000000005 and it will convert into 5e-007 exclusively when you re-open the shader. :P So, that is the base scale TG wants you to use. Forcing it does not mean it will work... lol

You can enter smaller amounts. TG doesn't limit you to 5e-007. I can't reproduce the result you got.

Matt
Just because milk is white doesn't mean that clouds are made of milk.