Colored Coating Absorption

Check out our technology advances and new features.
User avatar
giannis
Thea Developer
Thea Developer
Posts: 7986
Joined: Sun Jul 06, 2008 8:25 pm
Location: Athens, Greece
Has thanked: 11 times
Been thanked: 6 times

Mon Jul 13, 2015 3:07 pm

Dear friends,

we present a small advance in Thea material system, useful for those that aim for extra fine details when rendering.

This advance is about the coating absorption that can be wavelength dependent. The central idea is that the user defines now the absorption color at certain depth inside the coating (typically, 100 micro meters) using a standard color/texture control. This color becomes then the dominant one for any reflections coming from layers underneath.

Since the actual distance traveled by the reflected rays varies with the angle, the colored absorption creates a subtle but still observable effect where there is a simultaneous hue and saturation shift. The effect is "indeed there in real life" and can be seen in cases like metallic car paints and tinted wood varnish.

I attach two renders of a model, where you can see the transition and hue shift with viewing angle. This is more evident as you see nearer the edges of the car.
Lambo_car_paint_coating_with_absorption_yellow_orange.jpg
Lambo_car_paint_coating_with_absorption_purple.jpg
Best wishes
Science may limit knowledge but should never limit imagination - Bertrand Russell
User avatar
Rombout
Posts: 15254
Joined: Tue May 12, 2009 12:42 am
Location: Curacao, Netherland Antilles
Has thanked: 31 times
Been thanked: 272 times

Mon Jul 13, 2015 4:46 pm

Is this a addon to the current coating? this also had something about wavelength or thickness
User avatar
PixelMango
Licensed User v1.5
Licensed User v1.5
Posts: 155
Joined: Sat Feb 01, 2014 9:18 pm
Has thanked: 0
Been thanked: 0

Mon Jul 13, 2015 5:04 pm

giannis wrote:Dear friends,

we present a small advance in Thea material system, useful for those that aim for extra fine details when rendering.

This advance is about the coating absorption that can be wavelength dependent. The central idea is that the user defines now the absorption color at certain depth inside the coating (typically, 100 micro meters) using a standard color/texture control. This color becomes then the dominant one for any reflections coming from layers underneath.

Since the actual distance traveled by the reflected rays varies with the angle, the colored absorption creates a subtle but still observable effect where there is a simultaneous hue and saturation shift. The effect is "indeed there in real life" and can be seen, typically, in case of metallic car paints.

I attach two renders of a model, where you can see the transition and hue shift with viewing angle. This is more evident as you see nearer the edges of the car.
Lambo_car_paint_coating_with_absorption_yellow_orange.jpg
Lambo_car_paint_coating_with_absorption_purple.jpg
Best wishes
"Fresnel" option in Thea Materials?
User avatar
Rombout
Posts: 15254
Joined: Tue May 12, 2009 12:42 am
Location: Curacao, Netherland Antilles
Has thanked: 31 times
Been thanked: 272 times

Mon Jul 13, 2015 10:44 pm

We also get a fresnel ramp texture, did you see other preview?
I believe Thea already uses Fresnel, but now we can manually tweak it with the fresnel ramp texture.

This effect however is what happens when color is seen through a coating at certain angles. Its something different than fresnel i think, not sure here.
User avatar
giannis
Thea Developer
Thea Developer
Posts: 7986
Joined: Sun Jul 06, 2008 8:25 pm
Location: Athens, Greece
Has thanked: 11 times
Been thanked: 6 times

Tue Jul 14, 2015 4:15 am

Rombout wrote:Is this a addon to the current coating? this also had something about wavelength or thickness
Yes! It is a small addition that is another texture controlled by thickness.

This is not related to Fresnel curve tweaking but to absorption. It has an effect when there are additional layers under the absorving coating. The reflectance of those layers under the coating is then modulated by a combination of the absorption map + thickness + absorption physical formulas.

Best wishes
Science may limit knowledge but should never limit imagination - Bertrand Russell
User avatar
Rombout
Posts: 15254
Joined: Tue May 12, 2009 12:42 am
Location: Curacao, Netherland Antilles
Has thanked: 31 times
Been thanked: 272 times

Tue Jul 14, 2015 5:10 am

Ive tried the current absorption couple times never got it to work or quite understand well how it worked. The manual isnt sufficient in that i believe. Coating layer also has absorption function, is this sort of the same function than?
User avatar
giannis
Thea Developer
Thea Developer
Posts: 7986
Joined: Sun Jul 06, 2008 8:25 pm
Location: Athens, Greece
Has thanked: 11 times
Been thanked: 6 times

Tue Jul 14, 2015 6:35 am

Rombout wrote:Coating layer also has absorption function, is this sort of the same function than?
It is part of the new coating description. Patrick will make a small presentation with upcoming release.

Best wishes
Science may limit knowledge but should never limit imagination - Bertrand Russell
User avatar
GreenUser
Posts: 1131
Joined: Sat Apr 24, 2010 8:09 am
Location: California, USA
Has thanked: 0
Been thanked: 0

Thu Jul 16, 2015 11:21 pm

Perhaps a picture of the car without the new feature next a picture with the feature on would help show off what it's doing?
User avatar
giannis
Thea Developer
Thea Developer
Posts: 7986
Joined: Sun Jul 06, 2008 8:25 pm
Location: Athens, Greece
Has thanked: 11 times
Been thanked: 6 times

Fri Jul 17, 2015 8:26 am

GreenUser wrote:Perhaps a picture of the car without the new feature next a picture with the feature on would help show off what it's doing?
If I am not mistaken, the dominant color on the car comes from the absorption itself; it is not the color of diffusion or reflectance. I will check with Patrick, whether he can quickly make a render without the absorption but my expectation is that you will see a more "flat" gray coloring of the car.

Best wishes
Science may limit knowledge but should never limit imagination - Bertrand Russell
User avatar
patricks
Thea Technical Artist
Thea Technical Artist
Posts: 2375
Joined: Fri Jul 18, 2008 2:51 pm
Location: Germany & Palma de Mallorca/Spain
Has thanked: 0
Been thanked: 0

Fri Jul 17, 2015 9:31 am

on the yellow/orange Lamborghini car, its only the absorption color that we are seeing as the underling diffuse color is white .... just like its made in reality ;)

Greetings,
Patrick
" Poets say science takes away from the beauty of the stars - mere globs of gas atoms.
I too, can see the stars on a desert night, and feel them. But do I see less or more ? "

Richard P. Feynman
Locked