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  A few questions (Message 1 to 9 of 9)  
From: Andreas
Subject: A few questions
Date: 6 Jul 2008 08:50:00
Message: <web.4870bea283c1c1ea877851dc0@news.povray.org>
Hi!

I'm relatively new to POV-Ray, and I have some questions regarding a small
project I'm working on.

For one thing, I'd like to create a lava flow of sorts, which would illuminate
the surrounding area. I've tried to make the flow hollow and use it as a light
source, but that didn't seem to work. So I made a flow with high ambiance
levels, and used radiosity, which would light up the the canal in which the
lava flows. However, this does not light up any objects further away. Any
suggestions on this matter?

The second question is about texturing. I'd like to make a whip (bullwhip to be
exact..), but I can't seem to get the texture (braids) to follow the surface.
So far I've tried sphere_sweep and a 3D model which I've made, but nothing
seems to work correctly.
On the topic of texturing, I've thought about using two layered textures rotated
to be perpendicular to each other to simulate the braids, but does anyone have a
better approach?

Thank you for any tips and tricks you can share


Andreas


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From: Alain
Subject: Re: A few questions
Date: 6 Jul 2008 12:25:25
Message: <4870f1f5@news.povray.org>
Andreas nous illumina en ce 2008-07-06 08:46 -->
> Hi!
> 
> I'm relatively new to POV-Ray, and I have some questions regarding a small
> project I'm working on.
> 
> For one thing, I'd like to create a lava flow of sorts, which would illuminate
> the surrounding area. I've tried to make the flow hollow and use it as a light
> source, but that didn't seem to work. So I made a flow with high ambiance
> levels, and used radiosity, which would light up the the canal in which the
> lava flows. However, this does not light up any objects further away. Any
> suggestions on this matter?

"hollow" enable an object to contain some media, it don't have any other function.
You can make the lava transparent, or add "no_shadow", and put some light_source 
inside of it.
Your idea of using radiosity is the more realist way of doing it. If it don't 
light up farther objects, it can be because:
  - there is some obstacle between the "lava" ant that object. (very probable) 
If the lava is inside a trench, it will only light the trench and things that 
are over it.
  - the object is to far away for the "light" coming from the lava to have a 
significant offect. Give the lava a very high ambient value to thest that, like 
ambient 100000. ANYTHING that is still dark don't have a line of sight to the lava.
  - you may not have enough radiosity ray traced and you miss the lava. Try 
increasing the count value, it can go as high as 1600, to something like 200 to 500.
If the scene is inside something like a cave or tunel, you may need to increase 
recursion_limit to 4, 5, or maybe some more. Don't overdo that, there is a point 
of reduced return.

Do you have some fumes that you'd like to be lighted by the lava? In that case, 
you need to have actual lights as radiosity don't shine on media.

> 
> The second question is about texturing. I'd like to make a whip (bullwhip to be
> exact..), but I can't seem to get the texture (braids) to follow the surface.
> So far I've tried sphere_sweep and a 3D model which I've made, but nothing
> seems to work correctly.
> On the topic of texturing, I've thought about using two layered textures rotated
> to be perpendicular to each other to simulate the braids, but does anyone have a
> better approach?
> 
> Thank you for any tips and tricks you can share
> 
> 
> Andreas
> 
> 
You can go the hard way of using 3 sphere_sweep to actualy make your braid. You 
can then use a very plain texture as the aspect will be provided by the actual 
shape. In this case, I'd recomend using 3 slightly different textures, one for 
each strip.
If you use a modeler, you should turn on uv maping. Apply the texture to the 
straight whip, then make it bend and twist. That way, the texture should follow 
the shape.

-- 
Alain
-------------------------------------------------
Experience demands that man is the only animal which devours his own kind,
for I can apply no milder term to the general prey of the rich on the poor.
Thomas Jefferson


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From: Andreas
Subject: Re: A few questions
Date: 7 Jul 2008 16:45:00
Message: <web.48727f5dbb347ca52dfba1a30@news.povray.org>
Alain <ele### [at] netscapenet> wrote:
> Andreas nous illumina en ce 2008-07-06 08:46 -->
> > Hi!
> >
> > I'm relatively new to POV-Ray, and I have some questions regarding a small
> > project I'm working on.
> >
> > For one thing, I'd like to create a lava flow of sorts, which would illuminate
> > the surrounding area. I've tried to make the flow hollow and use it as a light
> > source, but that didn't seem to work. So I made a flow with high ambiance
> > levels, and used radiosity, which would light up the the canal in which the
> > lava flows. However, this does not light up any objects further away. Any
> > suggestions on this matter?
>
> "hollow" enable an object to contain some media, it don't have any other function.
> You can make the lava transparent, or add "no_shadow", and put some light_source
> inside of it.
> Your idea of using radiosity is the more realist way of doing it. If it don't
> light up farther objects, it can be because:
>   - there is some obstacle between the "lava" ant that object. (very probable)
> If the lava is inside a trench, it will only light the trench and things that
> are over it.
>   - the object is to far away for the "light" coming from the lava to have a
> significant offect. Give the lava a very high ambient value to thest that, like
> ambient 100000. ANYTHING that is still dark don't have a line of sight to the lava.
>   - you may not have enough radiosity ray traced and you miss the lava. Try
> increasing the count value, it can go as high as 1600, to something like 200 to 500.
> If the scene is inside something like a cave or tunel, you may need to increase
> recursion_limit to 4, 5, or maybe some more. Don't overdo that, there is a point
> of reduced return.
>
> Do you have some fumes that you'd like to be lighted by the lava? In that case,
> you need to have actual lights as radiosity don't shine on media.
>
> >
> > The second question is about texturing. I'd like to make a whip (bullwhip to be
> > exact..), but I can't seem to get the texture (braids) to follow the surface.
> > So far I've tried sphere_sweep and a 3D model which I've made, but nothing
> > seems to work correctly.
> > On the topic of texturing, I've thought about using two layered textures rotated
> > to be perpendicular to each other to simulate the braids, but does anyone have a
> > better approach?
> >
> > Thank you for any tips and tricks you can share
> >
> >
> > Andreas
> >
> >
> You can go the hard way of using 3 sphere_sweep to actualy make your braid. You
> can then use a very plain texture as the aspect will be provided by the actual
> shape. In this case, I'd recomend using 3 slightly different textures, one for
> each strip.
> If you use a modeler, you should turn on uv maping. Apply the texture to the
> straight whip, then make it bend and twist. That way, the texture should follow
> the shape.
>
> --
> Alain
> -------------------------------------------------
> Experience demands that man is the only animal which devours his own kind,
> for I can apply no milder term to the general prey of the rich on the poor.
> Thomas Jefferson

The lava problem is fixed now; it was the distance which caused the problem, so
I just scaled things down a bit.

As for the whip, it seems like the sphere_sweep method is quite complicated, and
I do not have enough math skills to actually implement something like that, at
least not for a coiled whip.
Am I correct in assuming that I can use POV-Ray textures for the 3D mesh, and
still get the UV mapping to work seamlessly?

Thanks


Andreas


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From: stevenvh
Subject: Re: A few questions
Date: 9 Jul 2008 11:35:00
Message: <web.4874d988bb347ca5c0721a1d0@news.povray.org>
Hi Andreas,
please ask only one question per thread, and name the subject line properly. "A
question" is no good, because that's what we all have. :-)
Thanks


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From: Mike the Elder
Subject: Re: A few questions
Date: 9 Jul 2008 14:35:00
Message: <web.487503e8bb347ca55a8888d90@news.povray.org>
"Andreas" <jak### [at] abofi> wrote:
....
> As for the whip, it seems like the sphere_sweep method is quite complicated, and
> I do not have enough math skills to actually implement something like that, at
> least not for a coiled whip.
> Am I correct in assuming that I can use POV-Ray textures for the 3D mesh, and
> still get the UV mapping to work seamlessly?
>
> Thanks
>
>
> Andreas

I've taken a shot at the whip and will shortly post the image and source files
in their respective binary topics. I hope it helps.

Best Regards,
Mike C.


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From: Andreas
Subject: Re: A few questions
Date: 10 Jul 2008 19:15:00
Message: <web.487696d4bb347ca5cff607c40@news.povray.org>
"Mike the Elder" <nomail@nomail> wrote:
> "Andreas" <jak### [at] abofi> wrote:
> ....
> > As for the whip, it seems like the sphere_sweep method is quite complicated, and
> > I do not have enough math skills to actually implement something like that, at
> > least not for a coiled whip.
> > Am I correct in assuming that I can use POV-Ray textures for the 3D mesh, and
> > still get the UV mapping to work seamlessly?
> >
> > Thanks
> >
> >
> > Andreas
>
> I've taken a shot at the whip and will shortly post the image and source files
> in their respective binary topics. I hope it helps.
>
> Best Regards,
> Mike C.

I've gotta say, that looks very good! To use icosahedrons to simulate the braids
is something I never would have thought possible. I'll experiment with the code
and see if I can get a more realistic texture and so on.
Thank you very much for your help! That goes for everyone of course :) Hopefully
I can now get a decent-looking scene together with everything I've learned here.


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From: Mike the Elder
Subject: Re: A few questions
Date: 11 Jul 2008 08:15:01
Message: <web.48774d9abb347ca55a8888d90@news.povray.org>
"Andreas" <jak### [at] abofi> wrote:
....
> I've gotta say, that looks very good! To use icosahedrons to simulate the braids
> is something I never would have thought possible. I'll experiment with the code
> and see if I can get a more realistic texture and so on.
> Thank you very much for your help! That goes for everyone of course :) Hopefully
> I can now get a decent-looking scene together with everything I've learned here.

Thanks for the feedback. One rather large flaw in my approach occurred to me
AFTER I posted everything. (Isn't that always the way?) I've applied the
texture to each individual icosahedron.  It would probably be MUCH better to
pull it out of there and apply it to the whole "union" and thus prevent the
loss of numerous subtleties inherent in any given texture.


Best Regards,
Mike C.


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From: Alain
Subject: Re: A few questions
Date: 11 Jul 2008 22:09:15
Message: <48781245.90605@netscape.net>
Mike the Elder nous illumina en ce 2008-07-11 08:10 -->
> "Andreas" <jak### [at] abofi> wrote:
> ....
>> I've gotta say, that looks very good! To use icosahedrons to simulate the braids
>> is something I never would have thought possible. I'll experiment with the code
>> and see if I can get a more realistic texture and so on.
>> Thank you very much for your help! That goes for everyone of course :) Hopefully
>> I can now get a decent-looking scene together with everything I've learned here.
> 
> Thanks for the feedback. One rather large flaw in my approach occurred to me
> AFTER I posted everything. (Isn't that always the way?) I've applied the
> texture to each individual icosahedron.  It would probably be MUCH better to
> pull it out of there and apply it to the whole "union" and thus prevent the
> loss of numerous subtleties inherent in any given texture.
> 
> 
> Best Regards,
> Mike C.
> 
> 
Applying the texture to each individual element have it's plus and minus.
The minus part is, mainly, that it takes more memory. It may also be somewhat 
slower, but only marginaly.
The plus is that the texture follows the shape, even if you change the curve used.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you know how to render a truly 
photorealistic compact disc, and you're not going to tell anyone
(least of all a POV user  ;)  ).
     -- Alex McLeod a.k.a. Giant Robot Messiah


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From: chang
Subject: Re: A few questions
Date: 24 May 2009 06:05:01
Message: <web.4a191ac3bb347ca5d2ccbc0a0@news.povray.org>
Hi!
  Now I am doing research about lava flow animation, I'm wondering whether I can
get your povray file. Look forward for your reply .
Thank You.

Best Regards
Chang


"Andreas" <jak### [at] abofi> wrote:
> Hi!
>
> I'm relatively new to POV-Ray, and I have some questions regarding a small
> project I'm working on.
>
> For one thing, I'd like to create a lava flow of sorts, which would illuminate
> the surrounding area. I've tried to make the flow hollow and use it as a light
> source, but that didn't seem to work. So I made a flow with high ambiance
> levels, and used radiosity, which would light up the the canal in which the
> lava flows. However, this does not light up any objects further away. Any
> suggestions on this matter?
>
> The second question is about texturing. I'd like to make a whip (bullwhip to be
> exact..), but I can't seem to get the texture (braids) to follow the surface.
> So far I've tried sphere_sweep and a 3D model which I've made, but nothing
> seems to work correctly.
> On the topic of texturing, I've thought about using two layered textures rotated
> to be perpendicular to each other to simulate the braids, but does anyone have a
> better approach?
>
> Thank you for any tips and tricks you can share
>
>
> Andreas


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