[Radiance-general] rtrace: -ospec options

[Marcin Gawroński]

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


---------------------------

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		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
1		
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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