Hi,

I am interested in simulating surface reflectance from smooth dielectric
and
rough surfaces, using 'state-of-the-art' (non-Lambertian) surface
reflection
behaviour (Oren-Nayar, Wolff, He, Beckmann-Spizzichino, etc).

Can POV ray help me do this?
What kind of reflectance model(s) does POV use anyway?
Where do I add code?
Is POV able to generate scientific-grade output?
Is there FAQ or userlist for these kinds of applications?

TIA,

Frank

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> What kind of reflectance model(s) does POV use anyway?

Standard POV uses the lambertian model for diffuse (with a brilliance factor
for adjusting it in a non-realistic fashion) and two empirical specular
reflection models for highlights.  MegaPOV include the blinn macrofacet
model, or at least something like it.

> Where do I add code?

For adding your own models, there's lighting.c in the source.  If you want
to adjust highlights, look at do_phong and do_specular.  For diffuse
shading, there's do_diffuse.  These are used in the function diffuse().
Raytraced reflections are handled in reflect().  Any lighting model should
be easy to add if you have a reference on how it works.

> Is POV able to generate scientific-grade output?
> Is there FAQ or userlist for these kinds of applications?

Try the links pages at www.povray.org.  I seem to recall this kind of
application to be popular among many POV-Ray users.

-Mike

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In article <3A125EFF.2D347298@hotmail.com>, Frank de Jong 
<fra### [at] hotmailcom> wrote:

> I am interested in simulating surface reflectance from smooth 
> dielectric and rough surfaces, using 'state-of-the-art' 
> (non-Lambertian) surface reflection behaviour (Oren-Nayar, Wolff, He, 
> Beckmann-Spizzichino, etc).
> What kind of reflectance model(s) does POV use anyway?

As mentioned, POV only does Lambertian diffuse reflection, MegaPOV also 
has a blinn highlight model. POV specular reflection(not highlights) is 
constant, MegaPOV has angle dependant and Fresnel reflection models.


> Where do I add code?

Mostly in lighting.c.


> Is POV able to generate scientific-grade output?

Depends on what you mean by "scientific-grade". POV is often used to 
produce images for visualization, and the scene language can do some 
simulations. However, there are many features that are not based on 
reality...so if you use these, forget about doing a simulation of real 
light.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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check out -

http://www.aetec.ee/fv/vkhomep.nsf/pages/povman2

-bep

Frank de Jong wrote:

> Hi,
>
> I am interested in simulating surface reflectance from smooth dielectric
> and
> rough surfaces, using 'state-of-the-art' (non-Lambertian) surface
> reflection
> behaviour (Oren-Nayar, Wolff, He, Beckmann-Spizzichino, etc).
>
> Can POV ray help me do this?
> What kind of reflectance model(s) does POV use anyway?
> Where do I add code?
> Is POV able to generate scientific-grade output?
> Is there FAQ or userlist for these kinds of applications?
>
> TIA,
>
> Frank

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Ben Paschke wrote:
> 
> check out -
> 
> http://www.aetec.ee/fv/vkhomep.nsf/pages/povman2
> 
Yes, POVMan could be used for simulating different surfaces without
recoding core POV-Ray, instead one could use Shading Language. This is
good for experimenting, and if there is dare need for speed, then one
can recode shader later in C into POV-Ray core.
"Advanced RenderMan" book contains example of Oren-Nayar BRDF, shaders
from this book could be downloaded in BMRT site:
http://www.bmrt.org/arman/materials.html
Look into file locillum.h, it contains Oren-Nayar model implementation
(along with Ward Larson's anisotropic model)

HTH

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