Thea Render Revision 486

Development versions, documentation, tutorials and application resources may be found here.

Moderator: patricks

Raoul
Licensed User v1.5
Licensed User v1.5
Posts: 34
Joined: Sat Oct 10, 2009 4:36 pm

hi Thomaz,

I tend to agree with your views on this and have recently done a few tests which seem to indicate that the blue cast from the physical sky is far less in reality.. in fact a 10am morning clear sky test showed quite a neutral tone, even in the shadows.

It looks as if the suns radiance should dominate by several factors, perhaps in a non-linear way. I find the matt-gray effect of an overcast day far more dominant than a clear blue sky, (when photographing textures for instance).. which i guess would make sense.

This however, is a very difficult test to do objectively since the brain, eyes and perceptions of tonal changes are constantly being adjusted to scene changes. It also requires careful setup of camera, white balance, scene and objects.

A possible solution may be to weight the sky colour dominance with 2 values, for direct and shadow.. similar to what you suggest and also in relation to white balance.

regards
User avatar
giannis
Thea Developer
Thea Developer
Posts: 7986
Joined: Sun Jul 06, 2008 8:25 pm
Location: Athens, Greece

ThomasHelzle wrote: When I saw the image of the physical sky sphere inside the library folder (cool!), I was reminded that I wanted to ask something for a long time:
Would it be possible to have a saturation value for the physical sky?
Thomas, you mean changing mostly the hue right? Although, it could be altered indirectly with the controls,
I agree it's not intuitive to set it. Would it makes sense to have R, G, B multipliers? i.e. a color to multiply
physical sky color with?
Science may limit knowledge but should never limit imagination - Bertrand Russell
Raoul
Licensed User v1.5
Licensed User v1.5
Posts: 34
Joined: Sat Oct 10, 2009 4:36 pm

.. this may help

I found when using standard render presets (without white balance), the sky cast seems to be far more prominent. However, with careful white balance, turbidity adjustment and slight tweaks to the sun's emmitance colour, its possible to get very close to the real thing.. that is comparing the render scene to a similar real life image.

There may still be a touch too much colour cast in the shadows and a very slight saturated aqua/pink tint to the sky/horizon, however, everything else looks very close indeed. The sun facing surfaces are almost identical on the render to the real image.

regards
ThomasHelzle
Licensed User v1.5
Licensed User v1.5
Posts: 643
Joined: Wed Feb 16, 2011 2:03 pm
Location: Berlin
Contact:

Hi Raoul,

I honestly am not too much concerned with "realism" in this case. ;)

The physical sky model in itself is a rather non-realistic kind of realism anyway (since there's no clouds and no "weather") so I personally would rather eyeball the saturation to fit my intended look (and I guess I would end up somewhere between 0% to 40% in most cases).

Right now I always use HDRIs for the sky (that I can desaturate externally if need should be) and activate the sun manually, but it would be nice to be able to use the PS for simple things.

I personally think that - while physical correctness and simulation are wonderful things - 3D and rendering are still mostly artistic tools that need a certain freedom for the user to get to the intended look rather than to an arbitrary "pseudo-realistic" result .

Changing the white point isn't what I would want to do since it changes the overall color balance of the picture, including other light sources...

giannis:

thanks for your feedback.
Well, I personally am mostly concerned about the color saturation, less about the tone.
Multiplying with R,G,B values sounds rather non-intuitive for this I fear, since for desaturation you would have to reverse the influence of - for instance - blue by raising the other two components (at least if I understood you correctly) which would also produce weird looks in other areas I guess.
I tried to get closer to what I want with the available controls, but couldn't get a really overcast, greyish, desaturated sky that way (maybe I didn't do it right though).

If it would be possible, a saturation setting for the physical sky would be all I need.

As far as the color hues go, the only thing missing ATM IMHO is a better simulation of evening and night, where things go very yellowish in my tests, but that isn't extremely high on my list of priorities :-)


BTW. I just found the best feature of all - I now can re-render the material previews in the library!
I missed that in the former update :-)
Fantastic!!!!! :clap: Thank you so much!

Dallas RTs wonderful materials have never looked better than rendered with 30 passes... :-)

I am so happy that I found Thea! Brilliant!

Cheers,

Thomas
User avatar
Javadevil
Licensed User v1.5
Licensed User v1.5
Posts: 3705
Joined: Mon May 18, 2009 2:19 am
Location: Noosa
Contact:

It would be really handy to have Theas tone mapping tools available for HDRIs and physical sky.
The same tone mapping that we have for bitmaps.
I find the only way to do it now is to adjust it with relight.

cheers
User avatar
naudofr
Posts: 998
Joined: Fri May 21, 2010 7:32 pm
Location: Nice (France)

ThomasHelzle wrote:the only thing missing ATM IMHO is a better simulation of evening and night, where things go very yellowish in my tests
Yes, I agree. It would be great to have this.
User avatar
jenujacob
Licensed User v1.5
Licensed User v1.5
Posts: 459
Joined: Mon May 11, 2009 5:44 pm

naudofr wrote:
ThomasHelzle wrote:the only thing missing ATM IMHO is a better simulation of evening and night, where things go very yellowish in my tests
Yes, I agree. It would be great to have this.
how bout a moon sky system? similar to the sun sky system??? would it be hard to come up with??
Win10 x64 | Intel i9-10900K | GeForce RTX 3090 | GeForce RTX 2060| 64Gb Ram
User avatar
giannis
Thea Developer
Thea Developer
Posts: 7986
Joined: Sun Jul 06, 2008 8:25 pm
Location: Athens, Greece

ThomasHelzle wrote: As far as the color hues go, the only thing missing ATM IMHO is a better simulation of evening and night, where things go very yellowish in my tests, but that isn't extremely high on my list of priorities :-)
Actually the night sky needs a whole new approach; there is some literature about creating a realistic night sky but frankly I don't think it would be as good compared to using some nice HDR images, in both terms of quality and render speed. At least now, Thea can handle the HDR image with very good response in all modes (unbiased/biased). ;)

Btw, we have considered from time to time, using an improved day sky model. Perhaps it is time to upgrade the current one. :think:
Science may limit knowledge but should never limit imagination - Bertrand Russell
ThomasHelzle
Licensed User v1.5
Licensed User v1.5
Posts: 643
Joined: Wed Feb 16, 2011 2:03 pm
Location: Berlin
Contact:

Hi giannis,

well, even if the sky would be simply getting dark at one point would be a nice improvement over the yellowish tone it is getting now at night :-)

But an improved day sky model sound interesting for sure - as long as it contains an option to de-saturate it ;-)

Basically I'm fine with HDRIs anyway, the interesting part of the physical sky is animation and location IMHO and that it offers a one click way to get some light into a scene for testing.

Thanks a lot for your considerations!

Cheers,

Thomas
User avatar
Gaieus
Licensed User v1.5
Licensed User v1.5
Posts: 218
Joined: Mon May 11, 2009 3:24 pm
Location: Pécs, Hungary
Contact:

Well, how about something like this instead?
:D

http://vimeo.com/moogaloop.swf?clip_id=21162297

(Why is there no Flash code? Not everything is on YouTube)
Intel Core2 Duo E8400 @ 3.0 GHz | 4 (3.4) Gb RAM | nVidia GeForce 9600 GT (1 Gb)
Windows XP Home 32 bit | Latest SketchUp - or even later :roll: | Latest (public) Thea
Locked

Return to “Versions & Resources (Studio)”