[Radiance-general] Re: graphing radiance raytrace paths

[Jelle Feringa // EZCT / Paris]

Hi Greg,

Wow! Thanks for pointing that out to me, that seems quite close to what I
intend to do. I think 'graph' wasn't necessarily the appropriate term, since
often it implies 2d. In fact I'm looking for a way to capture the rays
traced in a rendering to a 3d (polygon) file, preferable colored according
to their illumination value. Maybe you've seen the Maya 6 feauture where
your able to visualize the global illumination cache in coloured points. (if
you haven't it might be interesting that I upload an image to my server)
I'd like to do something similar like that, but its important to trace the
whole path, right from the camera, all the way back to the light source it
emitted (sure, a lot of them will end up at the wall, but the more rays can
be traced to the source, the better) 

As I understood from the man pages, piping ximage (t) to rtrace is close to
what xshowtrace does, except that its output is numbers instead of graphic
lines superimposed on the rendering (by the way, there's no way to control
the interval of xshowtrace -s is there? Awesome soft! Thanks so much!)

So here's what I tried using this approach:

ximage someRendering.pic rtrace -ab 5 -oodLpnsm -h -x 1 -i   someOct.oct >
rays.txt

rays.txt:
4.524520e+00	5.080820e+00	3.480030e+00	-3.025107e-01	3.848206e-01
8.720094e-01	5.183396e+00	2.956487e+00	7.075498e+00	8.000000e+00
0.000000e+00	0.000000e+00	-1.000000e+00	boxSTri321	box321	
4.524520e+00	5.080820e+00	3.480030e+00	-4.554681e-01
-3.514263e-01	-8.179538e-01	4.254556e+00	2.586706e+00	3.585657e+00
-3.348016e-16	0.000000e+00	0.000000e+00	1.000000e+00	box0.b	box0

4.524520e+00	5.080820e+00	3.480030e+00	-9.447599e-02
-6.675847e-01	-7.385154e-01	4.712197e+00	4.079331e+00	1.935029e+00
-2.426444e-16	0.000000e+00	0.000000e+00	1.000000e+00	box0.b	box0



Still that type of data comes near, but wont be sufficient for the graph
that I intend to make. The kind of script would allow for:

-setting the maximum number of rays traced
-outputting the coordinated of each ray in XYZ values where rays intersect,
all the way up to their source.
-these rays would purely be casted from the camera, not selected points in
space as in the xshowtrace approach
-what could be great is that rays will be coloured according to their
luminance value.
-the graph should be dense enough that the architecture from which the rays
were cast from becomes present in the graph.

In the end it'll be a very beautiful and powerful image, exposing radiance
inner mechanism!

Cheers, and thanks again for your feedback!

Jelle