Radiosity for Beginners: Concerning form factors

Gammastrahler · 2004-04-21T07:13:47

Hi, i´m just reading a while about Radiosity Lighting and i have decided to implement it in my indoor rendering engine for static lighting, since my current lighting method handles shadows very badly. Although im still reading and need to get more knowledge, i have a question concerning form factors: Which approach is esier to implement? Im very confused by the Hemicube algorithm (i found a link here to a very good tutorial, but i have read it several times, the more foten i read about the hemicube stuff, the more i get confused about it ) So i think about determining the form factors by raytracing. what are the performance and accurracy issues compared to the hemicube algorithm. can someone tell me which method produces better quality? and what about the matrix solution? how is it actually performed? thanks for any help! greets Gammastrahler

Graphics and GPU Programming Programming

Started by Gammastrahler April 12, 2004 12:58 PM

27 comments, last by Gammastrahler 19 years, 12 months ago

ALX

122

April 16, 2004 04:36 PM

quote:Original post by Gammastrahler
Here is an image rendered with my latest code, after a few passes, including the exponetional response curve for color conversion and fixed some little bugs:

Doesn''t look too bad.

quote:
The problem i still have, that when rendering with too many passes, the scene still gets brighter and brighter until it is completely white.

Are you resetting the shot patch energy after each pass ?

quote:
The problem i have with those books and papers is, that they are all english and my english is far from good... so understanding radiosity is actual a language problem for me...

Yeah, many are badly written and error prone on top of that. If you have specific questions, feel free to email me. I can try to explain it in either German or French, if that helps.

Gammastrahler

150

Author

April 17, 2004 07:09 AM

quote:
Are you resetting the shot patch energy after each pass ?

Yes, after each pass, i set the shooted energy = 0, (defined as delta in my code)

quote:
Yeah, many are badly written and error prone on top of that. If you have specific questions, feel free to email me. I can try to explain it in either German or French, if that helps.

I would really appreciate that

German would be great, but i´ve never learned french

Could you give me your email address?

/EDIT
have overseen the "mail" link

i have sent you a mail...

[edited by - Gammastrahler on April 17, 2004 8:59:48 AM]

bakery2k1

712

April 17, 2004 08:03 AM

In ALX''s code, he has:

// Take differential area and shadow factor into account
ff *= Hij * S->area;

I know you have not computed any shadow factors, but in the code you posted, I can''t see where you are multiplying by the area of the sending patch. Are you in fact doing this?

Gammastrahler

150

Author

April 17, 2004 08:14 AM

Currently i don´t take area into account, since all my patches are the same size.

Gammastrahler

150

Author

April 17, 2004 08:58 AM

@ALX

I have encountered an error in my code: My form factors get greater than 1.0, some about 5.0 !!!!

Tessellator

1,402

April 19, 2004 07:56 AM

Hi,

Just thought I''d leave a note and say I''ve found this thread very useful; I wrote a radiosity preprocessor ages ago, but never got it quite right (too dark, too bright, too crap etc). Anyway, I think I might go back to it now to see if I can apply the stuff I''ve read here to it. I''d love to hear how Gammastrahler fixes it in the end!

cheers,
T

Gammastrahler

150

Author

April 19, 2004 11:23 AM

Hi,

here is a new image, i have fixed the problem with the images getting too bright, but now i have another problem: I get convergence after 10000+ passes...

I thought i could forget about area, but that was the error!!! Now, it works, although very slow and unflexible.

Here is an image rendered with 30000 passes, but still far from converged, since the effects of color bleeding are very small yet:

greets
Gammastrahler

Tessellator

1,402

April 20, 2004 04:19 AM

I see what you mean about the colour bleeding, but the results are still impressive all the same. How small are you patches? You seem to have a really nice and sharp edge to things such as the light in the image.

Thanks,
T

Gammastrahler

150

Author

April 21, 2004 07:13 AM

Each side consists of 128x128 patches... of course an performance overkill. But since i currently don´t compute vertex radiosities from my patches, as well as i don´t have support for lightmaps at the moment, the images look only good at a very high resolution (32x32 and above).

greets
Gammastrahler

Radiosity for Beginners: Concerning form factors

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Radiosity for Beginners: Concerning form factors

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