Detail in shadow

Started by yossam, March 12, 2013, 03:11:07 pm

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yossam

Could someone suggest some GI settings to enhance the detail in shadows. I am getting some really ugly(really black) shadows at 2,2,8. The sun is at 10 degrees and approximately 90 degrees to the right of the camera. Any help would be greatly appreciated.

cyphyr

It depends on the situation really but the default values are not to useful for shadow detail.
Certainly tick "GI Surface details", possibly "Super sample prepass" and take the "GI Relative detail" and "GI Sample quality" up a notch (2,3 first, see how that looks, then 3,3, see how that looks, then 3,4, see how that looks etc).
You can add in some "fill lights" and always of course you can save your image as an exr and open it in Photoshop and see if the detail is there anyway.
Hope this helps
Richard
www.richardfraser.co.uk
https://www.facebook.com/RichardFraserVFX/
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Ryzen 9 3900X @3.79Ghz, 64Gb (TG4 benchmark 6:20)
i7 5930K @3.5Ghz, 32Gb (TG4 benchmark 13.44)

yossam

Right now anything would help, appreciate the suggestions. I really like what your pic is developing into.  ;)

Tangled-Universe

There are a number of possible ways to do this, 4 come in my mind right now.

1) What are your other render settings? Most important: what's the detail setting?

GI is relative to the detail setting, that's why it's named "GI relative detail".
This means that for detail 0.5 and GI relative detail @ 2 you effectively have 0.5 x 2 = GI detail @ 1.
So with low detail settings you have also lower GI "coverage".
You can check this by looking at the number of dots in the GI prepass.
With GI 2/2 and render detail 0.5 you will have much less dots than with render detail 1.

GI quality sampling means that for every dot in the GI prepass the renderer will sample x amount of times, which is defined by this setting.
The more you sample, the more accurate the value is for each dot in the prepass.

GI surface details definitely helps, but even at low sun angles it can give unsatisfactory results + that GI surface details is horrendously slow.
Also, GI surface details is only suitable when you want more detail in fine shadows, say in vegetation.

So all in all I'd first make sure that you have enough of those GI dots in your shadow areas.
For terrain these are relatively large areas, often, so you probably don't need very high GI detail.
Upping samples is better and faster, allowing for a more accurate result.

This is all pretty heavy dependant on each scene, so without an example of the situation and knowing more about the other rendersettings its difficult to say.

2) An easier and quicker one is to increase the "strength on surface" parameter in the enviro light node.
Increase it to 1.5 or 2 and see if it is satisfactory.
This can give a bit unbalanced results which would require some post-processing.

3) Increase ambient colour from black to white in the atmosphere node.
This works best if you have a bit thicker haze in your atmosphere node.

4) always save as EXR

Of these 3 options I like to use a combination of 1, 2 and 4.
I don't want to spend too much time and memory on calculating GI, so I make sure that I'm not generating an insane number of dots for GI cache.
As a matter of fact you can increase GI to 8 or 10 and post the GI prepass as finished render, you can get it that dense :)
So when I think I have enough dots and enough sampling I usually increase the strength on surfaces in the enviro light a bit.
This should all be sufficient to get enough detail in the raw render which you can easily get right when you save as EXR and post-process accordingly.

Please show us what you got, so we can give a bit more accurate directions.

Cheers,
Martin

cyphyr

March 12, 2013, 05:48:35 pm #4 Last Edit: March 12, 2013, 06:14:55 pm by cyphyr
Thanks for that detailed answer (even though it wasn't my question), that's the best description of the GI settings I've read.
Cheers
Richard

ps also a thought (that I'm experimenting with now), increasing the "ray detail  padding" and the "GI prepass padding" may allow "little" more light bounces back into shadow areas (at a render time cost).
www.richardfraser.co.uk
https://www.facebook.com/RichardFraserVFX/
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Ryzen 9 3900X @3.79Ghz, 64Gb (TG4 benchmark 6:20)
i7 5930K @3.5Ghz, 32Gb (TG4 benchmark 13.44)

Tangled-Universe

Ray detail region padding calculates geometry subdivisions outside of the camera frustum.
Ray detail region padding calculates GI outside of the camera frustum.
Potentially the latter can influence your render, but I wouldn't place my bets on it too much.

yossam

Here goes.............crop of the worst problem areas.

Quality:.5
AA:4
GI:3,3,8
Enviro light:2 strength on surfaces

No post, just converted to jpg

Oshyan

Odd, that doesn't really look like a GI issue as your plants are very well and fully lit, even in shadow. I assume you're talking about the very dark/black surfaces, i.e. under the plants on the right, at the edge of the terrain. That looks like something else, a shading error, or misconfigured terrain shaders. What parts of the scene are rendering that way, is that just bare terrain? It looks clearly different than the plants, so I'm guessing it's not other objects, but rather the terrain itself. What happens if you make the terrain/surface color white?

- Oshyan

yossam

The funny thing about it, it wasn't there last night. I was working on the scene, trying to get the lighting better. I closed the program and when I opened it back up today, the black spots were there.

I am doing a crop render without the populations to see if it is a shader issue. Will post when finished.

Oshyan

That especially makes it sound like not a GI issue...

- Oshyan

yossam

Here goes........there are some dark spots in the terrain and I think that the plants are making it worse when the shadows of the populations are there. I lightened up that particular shader and am doing another crop.

bobbystahr

Wouldn't Ambient Occlusion and a Soft Shadow sun help with this dark shadows problem...seems someone once suggested that to me
something borrowed,
something Blue.
Ring out the Old.
Bring in the New
Bobby Stahr, Paracosmologist

Hannes

March 24, 2013, 09:52:56 am #12 Last Edit: March 24, 2013, 09:56:02 am by Hannes
I made a little test after I downloaded one of the great models of this website:
http://www.planetside.co.uk/forums/index.php/topic,15831.0.html
I imported a model into TG, created the materials and made a test render with the default GI settings and Render: Detail/AA: 0.6/6.
It looks dull and the wheels seem to float.
Then I checked GI surface details and set the first two GI settings to 5/5. Better looking, but still not good. Rendering time almost four times longer.
The next thing was render overkill: I created an advanced fill light system: instead of three lights I used 24! Soft shadows on, diameter 1.
Looking much better, but rendering time was insane! (See the writing on the images)
(Original renderings had a width of 1024px)

I'd love to see an easier way to get a more realistic lighting environment for close ups...

inkydigit

that is an improvement, but 5.22 hrs?
ouch!
:)

Oshyan

What you need is Ambient Occlusion. To be honest I'm not sure just how capable the Enviro Light is in AO mode, but it's worth trying, add a second Enviro Light and set it to Ambient Occlusion. Clearly the other approaches aren't feasible and I wouldn't recommend them (e.g. massive amounts of fill lights, etc.).

- Oshyan