An image rendered using my build of the ray tracer code by Don Cross at
Saturday, December 12, 2015
Thursday, November 19, 2015
Monday, November 9, 2015
Trying to improve my problem solving.
Understand the problem...
-What is the unknown?
-What are the data?
-What is the condition?
Find the connection between the data and the unknown.
Consider auxiliary problems.
Obtain a plan of the solution.
Carry out the plan.
Examine the solution.
Monday, September 28, 2015
Thursday, September 10, 2015
Saturday, August 1, 2015
Saturday, July 4, 2015
Saturday, June 27, 2015
Another goal is to fully understand the below statements from a colleague, with regards to a particular renderer...
The k (kappa) term essentially relates to the absorption property, ie indirectly to the albedo of the material (Ks0, see further).
Then I guess you could turn eta into a color, so that could express a Ks90 type color.
I’d like to see two explicit colors, Ks0 and Ks90 blended with a shlick approximation.
It’s also really easy to relate the index of refraction to the reflectivity (ie Ks0 without the color component): R = [ ( 1 - ior ) / ( 1+ ior ) ] ^2
For instance, glass, with ior 1/1.5, leads to Ks0 = 0.04.
Note the 1/1.5 here, because we are considering glass as seen in the air (ior 1), ie going from air medium into glass medium.
This assumes Ks90 is 1 (or white) for most materials, tinted for metallic surfaces (hence the colored kappa).
...all the extra constants/parameters may relate to some type of spectral representation: I was talking about two colors (Ks0 and Ks90), but you could imagine describing them better than in RGB space and you could also imagine having more than these two samples along the fresnel curve.
This is all about what you are trying to simulate. (For instance, jewelry may benefit a lot from this).
Unfortunately, ...the renderer itself is *not* spectral, so the extra data (on top of the 3 stimulus RGB) will do nothing with most lights.
If you consider the Shlick approximation, then Ks0 would be the value on one end and Ks90 on the other (if your fresnel was based on V.N, reflectivity would be Ks0 where V.N = 1 going towards Ks90 on glancing angles where V.N = 0).
I speak about V.N above (which is the approach most people in the industry have taken for years), but remember that physically based models should be based on H, the halfway vector: so substitute H.N.