"Thomas de Groot" <t.d### [at] internlnet> schreef in bericht
news:43f9e7f5$1@news.povray.org...
>
> I shall test without this to see if there is a difference
>
....No. No difference   :-(

Thomas

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"Tek" <tek### [at] evilsuperbraincom> schreef in bericht
news:43fa041a$1@news.povray.org...
> Actually that's different to my problem, my media container is invisible
but
> the smoke media from my volcano gets more fogged than the top of the
volcano
> does at the same distance.
>
> I've managed to work round the problem by an extremely elaborate means:
>
> First, I tried using a global media instead of the fog, but that did
exactly
> the same thing. So then I replaced it with a huge box of media in front of
> the camera, differenced with the smoke-media's container. And I added a
copy
> of the air-media to the inside of the smoke media's container. All of this
> meant that pov finally got the message and gave me the result I was after,
> though it's a ludicrously elaborate work-round.
>
> --

Yes it's different, but somehow I cannot convince myself that there is not a
common problem here which concerns media and fog...

Thomas

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"Thomas de Groot" <t.d### [at] internlnet> schreef in bericht
news:43f970b9@news.povray.org...
>
> The container is, however, hardly or not visible when in front or
> intersecting a textured surface/object. In my Alien Cliff image, I cannot
> see it against the cliff.
>

This is not true unfortunately :-(
I looked acrefully at my image and saw strange patches that shouldn't be
there. So I made a new test with the fog, the media, and an isosurface
representing the cliff. This is the result. Note that the horizontal plane
does not show any artifact!!

Thomas

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Attachments:
Download 'Media_mist_test2.jpg' (17 KB)

Preview of image 'Media_mist_test2.jpg'

Thanks for giving the partial script earlier, Thomas. I just now got a look 
at a rendering of that here and saw the container bubble this time. I was 
going to ask if you had POV 3.6.1a or the 3.6.1b but I guess that's not the 
reason anyhow.

I didn't know you were using two fogs together before this point in time, 
thinking it was only media and one fog. I have no idea why the two fogs 
cause the media container to appear.

Bob H

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"Bob Hughes" <omniverse@charter%net> schreef in bericht
news:43fae38b$1@news.povray.org...
> Thanks for giving the partial script earlier, Thomas. I just now got a
look
> at a rendering of that here and saw the container bubble this time. I was
> going to ask if you had POV 3.6.1a or the 3.6.1b but I guess that's not
the
> reason anyhow.
>
> I didn't know you were using two fogs together before this point in time,
> thinking it was only media and one fog. I have no idea why the two fogs
> cause the media container to appear.
>

Thank you Bob, for taking time to look into this. Which shows again, by the
way, that it is always important to give complete information. Small details
(like one or two fogs) can easily be overlooked when just asking questions.

In fact, in the latter case, it is not the fog which causes the container to
appear! The container is carved out of the isosurface whether there is a fog
or not! I am puzzled because I cannot find any document treating this
matter. But I may be overlooking the obvious (I wouldn't be surprised).

So I end up with two problems.
1. interaction media and 2 fogs
2. interaction media and isosurface

Thomas

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"Thomas de Groot" <t.d### [at] internlnet> wrote:
> So I end up with two problems.

I've been having a play with this, and I have a couple of conclusions.

> 1. interaction media and 2 fogs
It's not the media. It appears to be a fog problem - if you take out the
interior block, the (now totally invisible) container object still shows up
if you use more than one fog. Unless someone knows a way around this, I
guess you'll have to fake one of the fogs with media (!).

> 2. interaction media and isosurface
Again, it's the container object intersecting the isosurface that seems to
cause the problem. Try raising the accuracy of the isosurface (i.e., use a
lower accuracy value). That worked with my tests.

Hope that's of some use

Bill

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>> 2. interaction media and isosurface
>Again, it's the container object intersecting the isosurface that seems to
> cause the problem. Try raising the accuracy of the isosurface (i.e., use a
> lower accuracy value). That worked with my tests.

Oh, isosurface has a keyword for that, it's all_intersections. Won't help 
the fog bubble any but should eliminate those empty places where another 
object is in contact with a isosurface. There's also a way to give it a 
certain number of possible "intersections", the Help tells something about 
it. I wasn't paying any attention to those arches in that last image and 
only looked for the media container bubble. ;)

Bob H

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"Bob Hughes" <omniverse@charter%net> schreef in bericht
news:43fb7e31$1@news.povray.org...
> >> 2. interaction media and isosurface
> >Again, it's the container object intersecting the isosurface that seems
to
> > cause the problem. Try raising the accuracy of the isosurface (i.e., use
a
> > lower accuracy value). That worked with my tests.
>
> Oh, isosurface has a keyword for that, it's all_intersections. Won't help
> the fog bubble any but should eliminate those empty places where another
> object is in contact with a isosurface. There's also a way to give it a
> certain number of possible "intersections", the Help tells something about
> it. I wasn't paying any attention to those arches in that last image and
> only looked for the media container bubble. ;)
>

Thanks a lot, Bill and Bob,  for these thought.

Accuracy it is! I had forgotten that I had changed the default value for
faster render. Did not realise that it would also influence other things.
Very stupid... I had tried already increasing max_trace (or
all_intersection) but to no avail, so I was on the wrong track.

Remains the transparant object/fogs problem. Replacing one of the fogs by a
media is tricky to say the least, and will bring down my already very slow
render speed even more. I shall first try to leave it out altogether and see
what the image is like.

Again, thanks both of you for your help!

Thomas

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"Thomas de Groot" <t.d### [at] internlnet> wrote in message 
news:43fc16ed@news.povray.org...
>
> Accuracy it is! I had forgotten that I had changed the default value for
> faster render. Did not realise that it would also influence other things.

Good to know there was an explanation. :)  Wish you much luck getting that 
cliff scene done.

I tend to change accuracy only for changing effect of how textures appear, 
something I noticed early on when isosurfaces were first being implemented 
in POV or to see how the it's surface differs at varying values of accuracy. 
I leave it alone most of the time now.

Bob H

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"Bob Hughes" <omniverse@charter%net> schreef in bericht
news:43fc1c2a@news.povray.org...
> "Thomas de Groot" <t.d### [at] internlnet> wrote in message
> news:43fc16ed@news.povray.org...
> >
> > Accuracy it is! I had forgotten that I had changed the default value for
> > faster render. Did not realise that it would also influence other
things.
>
> Good to know there was an explanation. :)  Wish you much luck getting that
> cliff scene done.
>
> I tend to change accuracy only for changing effect of how textures appear,
> something I noticed early on when isosurfaces were first being implemented
> in POV or to see how the it's surface differs at varying values of
accuracy.
> I leave it alone most of the time now.
>

Thanks Bob. The scene will be finished eventually. :-)   I have noted that,
against the cliff, the media container is invisible (the fog is probably too
thin thin) so I left my two fogs in place. Started rendering again....
I mainly change accuracy for render speed or to test how different
isosurface settings looks, although I admit it doesn't change speed that
much in general. To avoid forgetting to set things back to normal, I should
leave it alone...

Thomas

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