[Radiance-general] Re: Help with transfunc

Sat, 31 Jan 2004 17:51:39 -0800

Obviously, I should have given this a little more thought.  I just
copied the function you had straight into the formula, without
doing anything to keep it in a legal range.  The following is better,
but since I don't know what you're trying to do with this formula,
you should probably think about fixing the range or the formula
yourself.

void brightfunc trans_mod
2 bound(0,1-.6667/Rdot,1) .
0
0

trans_mod trans surf_dens
0
0
7 1 1 1 0 0 1 1

Sorry.
-Greg

Quoting Mark Stock <[email protected]>:

> I tried what you suggest (and some minor variations of that with
> rview from a 3.6a release in December. The window popped up and
> I saw a handful of multicolored pixels (there's no color at all
> in my scene), and then SegFaulted. I'm going to try it with the
> new release, and with rpict, and see what's up with that.
> 
> Mark
> 
> On Tue, 27 Jan 2004, Greg Ward wrote:
> 
> > Hi Mark,
> >
> > This is what you want:
> >
> > void brightfunc trans_mod
> > 2 1-.6667/Rdot .
> > 0
> > 0
> >
> > trans_mod trans surf_dens
> > 0
> > 0
> > 7 1 1 1 0 0 1 1
> >
> > The modifier will alter the specular transmission, and the trans has no
> > diffuse component or specular reflection.  The reason transfunc didn't
> > work for you was because the specularity you can modify is only used
> > for light sources in that material.  You could use BRDTfunc, but the
> > above is simpler.
> >
> > -Greg
> >
> > > From: Mark Stock <[email protected]>
> > > Date: January 24, 2004 12:36:37 PM PST
> > >
> > > I am confused about the use of the transfunc. Function files took
> > > me a little while to understand anyways, but what I can't figure out
> > > is how to specify only a change in transmittance in a material.
> > >
> > >         mod transfunc id
> > >         2+ brtd funcfile transform
> > >         0
> > >         6+ red green blue rspec trans tspec A7 ..
> > >
> > > I'd like to render a mesh object in "x-ray" form, but visualizing
> > > its surface and not its volume. I'd like a material that diffuses
> > > and reflects no light, and transmits light based on the "thickness"
> > > of the surface (assuming that the object is a thin shell of fixed
> > > thickness). I'd like the transmittance to be something like
> > > 1.0-(const/Rdot), but when I try the following:
> > >
> > >         void transfunc meshcolor
> > >         2 1.0-A5/Rdot .
> > >         0
> > >         6 0.5 0.5 0.5  1 0.66667 1
> > >
> > > I've tried several different values for the function, and everything
> > > gives me a totally opaque object, or an "undefined function" error.
> > > I'd like to get something like this:
> > >
> > > http://mark.technolope.org/vort3d/bd10/run168_first_sphere/burn1/
> > > run05/save_0053.jpg
> > >
> > > Mark
> >
> > _______________________________________________
> > Radiance-general mailing list
> > [email protected]
> > http://www.radiance-online.org/mailman/listinfo/radiance-general
> >
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