[Radiance-general] Transparent textures (again)

[Gregory J. Ward]

Hi Axel,

The mixpict primitive uses the indicated function of the red, green and 
blue channels of an image to determine how much of one material to use 
versus another.  One of these materials may be "void", which I 
recommend instead of the "glass" primitive that you're using in your 
current example.  A "void" material is the same as a perfectly 
transparent surface, which glass is not.  I would also recommend using 
"glow" instead of plastic to show up your falsecolor lines as something 
not truly belonging to the scene.

Here is a more complete example:

void colorpict fc_val
7 red green blue sp.pic fc.cal fc_u fc_v
0
0

fc_val glow fc_glow
0
0
4 1 1 1 0

void mixpict mp
7 fc_glow void nonzero sp.pic fc.cal fc_u fc_v
0
0
--------
The file "fc.cal" looks like so:

{ Use false color contour image as selector }
nonzero(r,g,b) = if(max(r,max(g,b))-FTINY, 1, 0);
fc_u = Px;
fc_v = Py;
------
The mapping for fc_u and fc_v may need to be a little more 
sophisticated if your image and space don't match, or you can try 
transforming the colorpict and mixpict primitives to match these 
coordinates, similar to how it's done for picture.cal.  Let me know if 
you need help with this part, and be specific with your questions (it 
helps a lot).

-Greg

> From: "Axel Jacobs" <a.jacobs at londonmet.ac.uk>
> Date: March 2, 2005 3:20:05 PM PST
> ...
> I would like to map the falsecolor illuminance image back into the room
> onto a new surface at working plane height to make the result more
> understandable. For this, the background of the falsecolor contour line
> image should probably be black, but this is no problem. The false 
> colour
> lines would appear to be hovering in the room. I saw something similar 
> in
> a demo of some commercial lighting software, but don't remember where.
>
> I think my problem is the cal file (PAB named his one picture_UV.cal)
> which is often referred to, but never given as an example. Since my 
> object
> is a nice'n'easy plane, would it be possible to use picture.cal that 
> comes
> with RADIANCE?