Dear Group

I use Radiance for a few years, and I handled with different problems so far. Now I have to complicated problem and I need some help. I engage in energy transport in participating media (rtrace with parameter –me).

As I read in ‘Rendering with Radiance’ value of expression

L(s) = L(0)*ext-(kappa*s) (assume albedo omega=0) (1)

is computed ‘after all the ray-surface interactions’ (page 591-592)

Is this formula computed for each ray, and then values connected with all rays are added? (it seems to me it is) Or maybe first values for all rays are added and after expression (1) is computed?

I need for my algorithm data connected with single ray: the value L(0) and distance s.

I tried to use rtrace with some options (all parameters are presented below – file: render_h.opt):

- ‘-otl’ – to get the distance from origin to object (s), but I’m not sure if s = l (l – effective length of ray)

- ‘-otv’ – to get value of each ray traced, but I get a table of zero values (something is wrong, I don’t know what)

Is this possible to compute L(0) and s (for each ray traced) using rtrace with some options at all? (I tried to analyze source codes of Radiance programs to find out it, but I’m not a programmer and it’s to complicated to me to understand it)

Best regards

Marcin Gawronski

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Attachments (my files):

- start: START.BAT

oconv S1.txt > pros.oct

rtrace @render_h.opt -h '-ospec' pros.oct <punktyS1.txt> ou-S1.txt

erase pros.oct

pause

- geometry and materials: S1.txt:

# material o odbiciu 0.2

void plastic odb0.2

0 0 5 0.3 0.3 0.3 0 0

# material o odbiciu 0.3 void plastic odb0.3 0 0 5 0.3 0.3 0.3 0 0

# przypisanie swiecacemu materialowi mat.dist rozkladu rozklad.dat

void brightdata mat.dist 5 noneg rozklad.dat illum.cal il_alth il_azih

0 9 1 0 0 0 -1 0 0 0 -1

# material S1 o odbiciu 0.7 rozkladzie mat.dist

mat.dist illum S1

1 odb0.2 0 3 16737.3478 16737.3478 16737.3478

# source

S1 polygon zrodlo1

0

0 12 0 0 1

0 1 1

1 1 1

1 0 1

odb0.3 polygon nazwa 0 0 12 0 0 0

0 1 0

1 1 0

1 0 0

source distribution (rozklad.dat):

1

1 0 37

1

- rtrace parameters: render_h.opt

-dp 4096

-ar 93

-ms 0.03

-ds .05

-dj 0

-dt 0

-dc .75

-dr 3

-sj 1

-st 0

-ab 10

-aa 0.08

-ad 2048

-as 1024

-av 0 0 0

-lr 12

-lw .0005

-I

-me 0.2 0.2 0.2 (if nesessary)

- point: punktyS1.txt

0.1 0.1 0 0 0 0.01

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