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I have tried to make a disco-ball, wich gives you those nice spots on
the walls. However, povray doesn't seem able to do this: the reflection
of a beam of light from a spotlight via a mirror onto the wall. Am I
doing something wrong? Is there anyone out there who tried this also?
I've been looking through the docs that came with povray, but couldn't
find anything...
Regards, Jarich
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Jarich Koning wrote in message
<3545E851.54ECE5B1@mail.student.utwente.nl>...
>I have tried to make a disco-ball, wich gives you those nice spots on
>the walls. However, povray doesn't seem able to do this: the reflection
>of a beam of light from a spotlight via a mirror onto the wall. Am I
>doing something wrong? Is there anyone out there who tried this also?
>I've been looking through the docs that came with povray, but couldn't
>find anything...
You are right. POV-Ray (as most raytracers) does no specular reflection.
That means, lightbeams that hit a reflecting surface will not be reflected
to light up something else.
This is due to how raytracing works: Not the lightbeams are traced as they
leave the lightsource, but instead rays from the eye of the user are traced
to see if they "hit" anything and can be traced (probably via
reflection/refraction) to some lightsource.
A workaround: Instead of little mirrors on the discoball, make little holes
and place a lightsource inside of the ball (or something similar...)
Johannes.
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Jarich Koning wrote:
> I have tried to make a disco-ball, wich gives you those nice spots on
> the walls. However, povray doesn't seem able to do this: the reflection
> of a beam of light from a spotlight via a mirror onto the wall. Am I
> doing something wrong? Is there anyone out there who tried this also?
> I've been looking through the docs that came with povray, but couldn't
> find anything...
>
> Regards, Jarich
Use Povray 3.x and render with radiosity then you schould see any
reflection on the Wall
ALIL
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No, you still won't be able to see specular reflection. Sorry... even with
radiosity.
--
Lance Birch
Remove the smiley to e-mail.
http://www1.tpgi.com.au/users/ambient/lance
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The problem with seeing spots on the wall is that you have to trace the ray
from the opposite direction, i.e. from the light source to the eye.
POV-Ray traces from the eye to the light source, and since the wall
scatters light, there's no way to know that the ray needs to be traced back
to a specific light source that is creating a spot. One way around it
might be to make your disco ball a hollow sphere with a light source
inside, and holes in it. That way the solid parts of the sphere might cast
shadows on the wall where the light isn't hitting, and leave bright spots
where the light leaks through.
Just an idea. I haven't tried it.
--Gary.
Alil <e9725415@stud3.tuwien.ac.at> wrote in article
<35517749.D4BFCAEA@stud3.tuwien.ac.at>...
> Jarich Koning wrote:
>
> > I have tried to make a disco-ball, wich gives you those nice spots on
> > the walls. However, povray doesn't seem able to do this: the reflection
> > of a beam of light from a spotlight via a mirror onto the wall. Am I
> > doing something wrong? Is there anyone out there who tried this also?
> > I've been looking through the docs that came with povray, but couldn't
> > find anything...
> >
> > Regards, Jarich
>
> Use Povray 3.x and render with radiosity then you schould see any
> reflection on the Wall
>
> ALIL
>
>
>
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"Lance Birch" <:-)Lan### [at] tpgi comau> wrote:
> No, you still won't be able to see specular reflection. Sorry... even with
> radiosity.
Hmm, I wonder. Isn't it possible to also take into account the
specular reflections when calculating radiosity... I haven't check
how povray does it, but according to one my comuter graphic books
is should be possible.
/ Mathias Broxvall
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Mathias Broxvall (mbr### [at] swipnetseNOSPAM) wrote:
: > No, you still won't be able to see specular reflection. Sorry... even with
: > radiosity.
: Hmm, I wonder. Isn't it possible to also take into account the
: specular reflections when calculating radiosity... I haven't check
: how povray does it, but according to one my comuter graphic books
: is should be possible.
Is it just me or...? I wonder why povray doesn't calculate radiosity in
a scene which is seen reflected on a mirror.
--
- Warp. -
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Some say that POV-Ray doesn't do true radiosity, which may just mean that the
method is a little old. I hear many people are doing reflective light, reflective
caustics, and true area lights with radiosity. There is one guy who posts to
c.g.r.r that has a method he calls photon mapping that looks like it would work. I
also tried a program called helios that some others may have run across on the
web. There is a book that goes along with it. I tried the program and it does
rendering entirely with radiosity, no raytracing. Only takes a minute or so to
render with it too, and the results are quite amazing. Makes smooth area lights
and simulates light bouncing all over the place. I'm thinking the POV-Ray team
with adress radiosity in version 4, since they don't seem to be working on it now
and it's still considered experimental.
-Mike
Nieminen Mika wrote:
> Mathias Broxvall (mbr### [at] swipnetseNOSPAM) wrote:
> : > No, you still won't be able to see specular reflection. Sorry... even with
> : > radiosity.
>
> : Hmm, I wonder. Isn't it possible to also take into account the
> : specular reflections when calculating radiosity... I haven't check
> : how povray does it, but according to one my comuter graphic books
> : is should be possible.
>
> Is it just me or...? I wonder why povray doesn't calculate radiosity in
> a scene which is seen reflected on a mirror.
>
> --
> - Warp. -
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Jarich Koning <s96### [at] mailstudentutwentenl> writes:
>
> I have tried to make a disco-ball, wich gives you those nice spots on
> the walls. However, povray doesn't seem able to do this: the reflection
> of a beam of light from a spotlight via a mirror onto the wall. Am I
> doing something wrong? Is there anyone out there who tried this also?
> I've been looking through the docs that came with povray, but couldn't
> find anything...
Inspired by your request I tried it myself. I faked the reflections
using cylindrical lights. The directions and positions were calculated
by povray. Since there aren't any other objects in the scene between
the light source(s) and the disco ball, it was easy to test whether or
not the disco ball blocks the light path.
I have posted the image in povray.binaries.pictures as well as the source
code. Be aware that the image needed 73.5 hours to finish on my Pentium 150.
Perhaps I will add some nice back scenary and animate it, if I have enough
time...
ThW
--
Tho### [at] uni-konstanzde
http://www.informatik.uni-konstanz.de/~willhalm/
Tschieses lavs ju
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