"Kenneth" <kdw### [at] earthlinknet> wrote:
> "s.day" <s.d### [at] uelacuk> wrote:
> > Wow! thanks for all the replies.
> >
> > No media in the scene to be causing any issues...
> >
>
> A beautiful scene, and very complex (which makes it difficult to nail down the
> problem, I'm sure.)
>
> In looking at your scene code, I see that there are lots of spotlights that
> actually DO make use of media in some way. In the current version of POV-Ray,
> there are *multiple* problems associated when using media, radiosity and
> spotlights, which can cause really strange visual aberrations to appear in
> places you wouldn't expect. So far, I've only posted info about one such
> problem (not using radiosity). But there are others.
>
> Here's the link...
>
http://news.povray.org/povray.general/thread/%3Cweb.45125ba9d84b4b77cc29cf380@news.povray.org%3E/
>
> and the link to the associated image...
>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.45125e6ed84b4b77cc29cf380%40news.povray.org%3E/?ttop=2674
26
> &toff=900
>
> Another problem is that radiosity illumination from media does not show up on
> any objects (or parts of objects) that are inside a media-filled spotlight
> cone. Said another way, the media IN the cone doesn't generate radiosity
> illumination on objects that are embedded in it. I think that's a problem with
> the spotlight itself.
>
> My suggestion would be to run your complete scene--radiosity and all-- with
> UseTestTex=1 rather than 0 (which will turn off your media) and see if the
> black spots still appear. A long and laborious testing process, to be sure!
>
> Ken W.


Hi Ken,

Thanks for taking the time to download/read the code, it must be almost as much
of a challenge as finding the cause of this problem with my lack of comments. I
had forgotten about the media used with the spotlights (that's the problem with
re-rendering 3 year old scenes). However, for the renders I have posted I was
using useTestTex=1 so media would not have been used/affected this.

I have done several more tests but so far have not found the cause. My first
tests were to revert to the default radiosity settings then go through and
adjust each item one at a time to the settings that caused the problem. All
these renders were OK (and much quicker).

I have also managed to complete a render with reasonably high quality settings:

    pretrace_start 0.08
    pretrace_end   0.01
    count 500
    nearest_count 10  // was 20
    error_bound 1     // was 0.08
    recursion_limit 4
    low_error_factor .5 // was 0.9
    gray_threshold 0.0
    minimum_reuse 0.015
    brightness 0.8
    adc_bailout 0.01/2

which rendered fine, I am using the saved data from this trace to render at
5250x3500 with focal blur/isosurfaces and spotlights with media etc.. So far
the estimate for this render is about 5 months so I hope I am happy with it at
the end!!

As the PC still has several cores sitting their idle I am trying a smaller
render with the settings that caused the problem to see if image size has an
effect. I am still hoping to track down the cause of this even if the current
render is OK (I can't stand a mystery) I just wonder if I will manage to find
the cause before the other render has finished..

Sean

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