[Radiance-general] Assistance required with Rendering error

[Carsten Bauer]

Hi DAI-crew,

the artifacts stem most likely from a special random generator  used for all 
kinds of ray jittering applied in the process of penumbra generation. I don't 
really know why this is done, because pictures often look rather strange with 
these patterns. 

Luckily, however, Radiance provides a way to switch this off, just recompile 
the whole stuff with the compiler flag -DMC, and the penumbras will look much 
better.

You might experience problems in compiling with -DMC, at least I did (with 
Linux). I had to change the following:

in ray/src/common/random.h :

put line 71 in #ifndef MC exclusion:
 
#ifndef MC                               /*  <--- inserted */                                                                                                             
extern int      initurand(int size);                                                                                    
#endif                                     /* <---- inserted  */

in ray/src/rt/raycalls.c

the same with line 171ff:

#ifndef MC                              /* <--- inserted   */                                                                                                            
                                        /* initialize urand */                                                           
if (urperm == NULL)                                                                                             
                initurand(2048);                                                                                        
#endif                                    /* <-----inserted */

Apart from this general treatment really strong artifacts may also appear due 
some geometry error in the scene file (for example if a light source is 
partly cut by some object).

-Carsten