Baking - Anistropy Maps - Pretty please, help me.
polycounter lvl 12
Hey to all,
I was wondering how one goes about creating a system for Anistropy maps.
I did some reading, and for the life of me cannot understand why Anistropy systems works only on the Diffuse maps, while having their own specialized Map.
Here is the tutorial I have been reading off from, trying to understand the system.
http://stephenjameson.com/tutorials/anisotropic-shader-for-hair/
Again, my main problem is how would one go about making the map? Is there a dirty way? Can you convert Tangents to Aniso-Maps through a program? Any input would be much appreciated.
Cheers and thanks.
I was wondering how one goes about creating a system for Anistropy maps.
I did some reading, and for the life of me cannot understand why Anistropy systems works only on the Diffuse maps, while having their own specialized Map.
Here is the tutorial I have been reading off from, trying to understand the system.
http://stephenjameson.com/tutorials/anisotropic-shader-for-hair/
Again, my main problem is how would one go about making the map? Is there a dirty way? Can you convert Tangents to Aniso-Maps through a program? Any input would be much appreciated.
Cheers and thanks.
Replies
As far as I am aware there is no way to "bake" anisotropic directional information, as there isn't any production renderers that encodes molecular or microsufrace alignment in it's material definitions.
However you can paint an anisotropy map, or even just paint one channel and extrapolate the other.
I've hand painted in one once, which kinda sucked as an experience.
Ihave some ideas about good ways to do this, but I'll be testing them this weekend with my angel model. I'll post the results here later on.
Plus, I love technical stuff, usually its that 'need better technical graphics' stuff which bring aesthetics and style into play and makes them pop.
Actually, funny note, your angel model is what inspired me to do some anisotropy test outs for metal and hair, your model has so much potential for playing around with anisotropic effects, that I thought I might as well learn this, since with all the next gen stuff we're doing including robots and sci-fi stuffs, but was sorely disappointed when the closest thing I found was 8monkey having their own solution for Marmoset, which isn't available to the public.
Can't wait for you to finish your model, good luck with that!
The best option (for hairs case) would be to unwrap and rotate your shells in the up/down direction, so you only need a simple constant value of RG. Add a quick normal map and marry with a set of constant to make the 'noise' values appear would also be dandy.
But what about metal and other polished sci-fi stuff, which would benefit from said tech? They both serve the same idea from what I could read upon, but more complex stuff would certainly benefit from a map which guides the flow of the UV's direction.
It takes a 2 vector corresponding to the direction perpendicular to the anisotopic highlight. It defaults to 1,0 which is up to down. Its range is the same as a normal map, that is -1 to +1 on both channels. However, for this particular map, just leaving a normal unpack of 0-1 won't harm it any.
Knowing that you can paint just the vertical component to the anisotropy and calculate the horizontal component. I was planning to do that for the bare metallic portions of Angel, though I may skip it, as I have a ton of other materials going on anyway.
Anyway, the anisotropy direction map, being two channel, can be viewed as a red/green texture. But since the anisotropy will be everywhere, you only need one channel to construct the other. Using Red for up and down grain the green portion is just 1-abs(r). This will only generate positive green values, but really, that should suffice for most applications, and saves a second texture channel for some other purpose.
For what its worth, I'm going to implement something close to the Marschner reflectance model on Angels's hair. Gonna have to simplify or modify it some I believe, as I don't have a way to make look up textures like NVidia did for the Nalu demo.
Unfortunately source code was lost and the app died of code rot.
I think in the latest toolbag the aniso material has been modified to take a more "common sense" type of input that you can paint yourself without too much trouble.
I also hit up their page, but still couldn't find anything about Aniso.
I cant seem to find anything. Including Marmoset Tuts. Stephens page is more a technical talk idea behind it and uses some tangent tricks versus a real direction map.
Check out this: http://www.polycount.com/forum/showthread.php?t=98844
An aniso tutorial for Toolbag is something that is sort of on my mind, but I need to do some more research and actually figure out how to use it myself first.:poly124:
Thanks, wouldn't have thought to use comb as search term.