[Radiance-general] Re: Photon map addition

[Greg Ward]

This is largely my fault for not taking the time to really go through 
the photon map changes to see what they were about.  I started looking 
through Roland's docs a year ago, and never got back to it.  I simply 
haven't had time to play with it, and I don't see the time appearing 
anywhere in the immediate future.

If the photon map had been implemented as a mkillum substitute, i.e., a 
separate program that creates light sources for Radiance, there would 
be no hesitation to include it in the main distribution.  In that case, 
there would have been no risk whatsoever to the renderer, and it 
wouldn't have affected any of the rendering options.  However, my 
understanding is that the photon map has been folded right into the 
main rendering code, with quite a few new options associated with its 
use.  This makes it critical to do a fitness evaluation before we fold 
it into the main source, and that requires testing.

We need to take a very careful look at this module's affect on the code 
as well as the rendering process -- does it support all material types 
(or at least do something reasonable with the types it doesn't 
support)?  Does it place any restrictions on light sources?  
Participating media?  How does it behave when the geometry gets 
complex?  Does it burden or otherwise affect the calculation when it is 
switched off?  Do we get the same results or nearly the same under all 
important circumstances?

These concerns must be answered, and I'm sure Roland can answer some of 
them.  For other concerns, I'll just have to pour over the source code 
and test it and test it.  It would be very helpful to me if Roland and 
I could get together and run through everything, but that hasn't 
happened, and e-mail gets mixed in with all the other activities we 
have going on, making communication slow and difficult.

I really appreciate the efforts Roland has put forth to get this out, 
and to keep it updated with the latest source changes on our end.  I 
know this is no small task, and it feels cruel to make new releases 
without incorporating his changes, because it just means more work for 
him without any real benefit.

It would help me to hear from users who have successfully applied the 
photon map.  I'd like to see how it helped them and hear what they have 
to say about it, on the list or off.  Theoretical discussions and 
people saying this is a "good idea" are useful only up to a point.  
Real experience is what matters, and that's what I need to hear from 
people.  I have not used the photon map myself at this point, so I have 
no direct experience of my own.

Thanks,
-Greg

> From: Roland Schregle <ganjatron@gmx.net>
> Date: November 30, 2003 5:04:25 AM PST
>
> Lars O. Grobe wrote:
>>> (...) Note that RADIANCE modified with pmap behaves exactly like 
>>> RADIANCE Classic unless you explicitly use pmap options. As such, 
>>> you don't need the original RADIANCE binaries anyway.
>>  Hi,
>> hmmm... maybe this has been on the dev-list before, but if this 
>> feature can be used like this without problems - will it be included 
>> in the main distribution of radiance one day?
>
> Good question -- that's up to Fraunhofer and Berkeley, I guess. I 
> don't expect that to be resolved anytime soon... :^(
>
> --Roland