Hello,

These look the same radiosity artifacts I get with POV 3.7b. It's a bug 
with the current (beta quality) radiosity calculation.

To get rid of them I just lower the count until they disappear. Of 
course, this will reduce the overall quality, but you can compensate by 
introducing a slight normal to the surfaces and keeping a low 
error_bound. I hope this helps.

Sam

Post a reply to this message

> These look the same radiosity artifacts I get with POV 3.7b. It's a bug 
> with the current (beta quality) radiosity calculation.

Interesting; since the original poster didn't say what POV-Ray version 
he was using.

Post a reply to this message

stbenge <stb### [at] hotmailcom> wrote:
> Hello,
>
> These look the same radiosity artifacts I get with POV 3.7b. It's a bug
> with the current (beta quality) radiosity calculation.
>
> To get rid of them I just lower the count until they disappear. Of
> course, this will reduce the overall quality, but you can compensate by
> introducing a slight normal to the surfaces and keeping a low
> error_bound. I hope this helps.
>
> Sam

Hi Sam,

Thanks for the info but this is version 3.6. I avoided 3.7 as I know the
radiosity feature is not working correctly yet.

Sean

Post a reply to this message

"s.day" <s.d### [at] uelacuk> wrote in message 
news:web.47da42f3d387c8867eb3d110@news.povray.org...
> stbenge <stb### [at] hotmailcom> wrote:
>> Hello,
>>
>> These look the same radiosity artifacts I get with POV 3.7b. It's a bug
>> with the current (beta quality) radiosity calculation.
>>
>> To get rid of them I just lower the count until they disappear. Of
>> course, this will reduce the overall quality, but you can compensate by
>> introducing a slight normal to the surfaces and keeping a low
>> error_bound. I hope this helps.
>>
>> Sam
>
> Hi Sam,
>
> Thanks for the info but this is version 3.6. I avoided 3.7 as I know the
> radiosity feature is not working correctly yet.
>
> Sean
>

Hi Sean,

I only say this because I didn't see anyone else mention it, but I imagine 
you've checked that it's not just the old coincident surfaces chessnut 
(which catches me out with embarrassing regularity).

Regards,
Chris B.

Post a reply to this message

"Chris B" <nom### [at] nomailcom> wrote:

> Hi Sean,
>
> I only say this because I didn't see anyone else mention it, but I imagine
> you've checked that it's not just the old coincident surfaces chessnut
> (which catches me out with embarrassing regularity).
>
> Regards,
> Chris B.


Hi Chris,

No it is not coincident surfaces (although I too have suffered with these many
times).

I have rendered this scene before (for povcomp) and it rendered OK.
The only differences with this render are higher radiosity setting and higher
resolution. The render I submitted to povcomp was without isosurfaces turned on
but I have also rendered at 1600x1200 with isosurfaces. (this version can be
found here:
http://news.povray.org/povray.binaries.images/thread/%3Cweb.42885c9a31d5b4de79fdcb760%40news.povray.org%3E/?ttop=266991
&toff=2000
).

For the 1600x1200 render I gathered radiosity stats at 800x600.

I was planning to do the final render at 5250x3500 and gather radiosity stats at
2625x1750.

Sean

Post a reply to this message

s.day wrote:
> For the 1600x1200 render I gathered radiosity stats at 800x600.
> 
> I was planning to do the final render at 5250x3500 and gather radiosity stats at
> 2625x1750.

Care to post your radiosity step 2 (after gathering) setting?  I 
personally never get quite the results I want if I render both steps at 
different resolutions and my step 2 settings work best like these:

   load_file "tmp.rad"
   minimum_reuse 0
   count 1
   error_bound EB+.1
   low_error_factor 1
   recursion_limit 1
   pretrace_start 1
   pretrace_end 1
   nearest_count 1

EB is error_bound from step 1.  It goes slightly smoother like this.

Post a reply to this message

Hmmm.... All this guessing...

S. Day, my suggestion is, that you publish the entire scene code and related 
graphics and INI files. This would allow us, to have some persons working on 
your scene to find out where the problem is.

Once we can try and try again, you should get soon an exact answer. I hope, 
this suggestion is okay for you. Once the black holes are fixed, your scene 
will become a beautiful scene.

Post a reply to this message

nemesis <nam### [at] nospamgmailcom> wrote:
> Care to post your radiosity step 2 (after gathering) setting?  I
> personally never get quite the results I want if I render both steps at
> different resolutions and my step 2 settings work best like these:
>
>    load_file "tmp.rad"
>    minimum_reuse 0
>    count 1
>    error_bound EB+.1
>    low_error_factor 1
>    recursion_limit 1
>    pretrace_start 1
>    pretrace_end 1
>    nearest_count 1
>
> EB is error_bound from step 1.  It goes slightly smoother like this.

Hi,

I have had similar issues to you but find rendering at 50% of the final
width/height to usually be acceptable (although comparissons may show that
rendering with 50% the radiosity quality at the correct resolution will be just
as good..).

I do not normally specify much for the second pass just set:

pretrace_start 1
pretrace_end 1
error_bound = same as step 1 (although I might try your technique in future).
recursion_limit = same as step 1
always_sample off

I do not really understand the radiosity settings very well I have a rough idea
of how most of them work but tend to resort to trial and error more than
educated guessing..

Sean

Post a reply to this message

"Sven Littkowski" <sven [] jamaica-focus [] com> wrote:
> Hmmm.... All this guessing...
>
> S. Day, my suggestion is, that you publish the entire scene code and related
> graphics and INI files. This would allow us, to have some persons working on
> your scene to find out where the problem is.
>
> Once we can try and try again, you should get soon an exact answer. I hope,
> this suggestion is okay for you. Once the black holes are fixed, your scene
> will become a beautiful scene.


Hi,

The scene code is on the povcomp site for all to use:

http://www.povcomp.com/entries/199.php

Just paste the radiosity settings from the first post into the file. The strange
thing is the only settings I changed from the previous render (which worked fine
at lower resolutions) were

error_bound from 0.1 to 0.08
recursion_limit from 2 to 5
count from 200 to 500
brightness from 0.9 to 0.8

Of these I guess error_bound is the most likely to cause the problem but I am
still not sure if it coulde be related to the resolution.. I should have an
idea by Monday morning.

Anyway, anyone who wants to try rendering this is OK with me (I hope you have a
spare PC and plenty of time though... but then if you are used to POV patience
is something of a necessity ;-)

Sean

Post a reply to this message

> The scene code is on the povcomp site for all to use:

sky_sphere ...

The radiosity engine only uses rays that travel finite
distances, sky_sphere and background are both an
infinite distance.  When a radiosity ray "leaks" thru
a seam, and then goes infinite, that ray is considered
pure black, which affects previous bounces of the
ray, coloring them black as well. Higher quality
settings means there are more rays to leak thru.

You should use a large inverted sphere for sky
in radiosity scenes, that way there will be no infinite
rays at all. That should reduce the artifacts.

Post a reply to this message