howdy, I have two questions for you guys.

1) What is the best way to light a scene containing a lot of glass. ie:
drinking glasses with liquid etc. I have tried multiple light sources
(point lights and area lights) but just cant seem to get it right. The
scene is either too light or two dark and the glasses all have very dark
regions in them. Should I encase the whole thing in a box or sphere to
increase the amount of ambient light?

2) This is a silly question of sorts, must you put a semi-colon at the
end of a declare statment? I always forget to, especially in multi-line
declares, and everything works fine for me.


-paul

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In article <38BFAAEE.4B962461@psu.edu>, Paul Daniel Jones 
<pdj### [at] psuedu> wrote:

> 1) What is the best way to light a scene containing a lot of glass. ie:
> drinking glasses with liquid etc. I have tried multiple light sources
> (point lights and area lights) but just cant seem to get it right. The
> scene is either too light or two dark and the glasses all have very dark
> regions in them. Should I encase the whole thing in a box or sphere to
> increase the amount of ambient light?

It sounds like you don't have max_trace_level high enough. Check out 
global settings and max_trace_level in the manual, it basically tells 
POV how many levels it can go into the scene, too few will cause 
disappearing reflections and dark areas. If this is the problem, it 
won't disappear no matter how many light sources you use.
Try adding this to the beginning of the scene:
global_settings {
    max_trace_level 24// 7 is the default, this often needs to be
                      // increased in scenes with reflection or
                      // transparent objects
}


> 2) This is a silly question of sorts, must you put a semi-colon at the
> end of a declare statment? I always forget to, especially in multi-line
> declares, and everything works fine for me.

It is not required in the current version, but might be in a future 
version. You had better get in the habit now, while the only problem it 
causes is a warning.(if it happens in a loop, all those warnings can 
also slow parsing down)

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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Paul Daniel Jones <pdj### [at] psuedu> wrote:
: the glasses all have very dark regions in them.

  Increase max_trace_level (and be prepared for a _long_ render).

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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Paul Daniel Jones wrote:
> 
> howdy, I have two questions for you guys.
> 
> 1) What is the best way to light a scene containing a lot of glass. ie:
> drinking glasses with liquid etc. I have tried multiple light sources
> (point lights and area lights) but just cant seem to get it right. The
> scene is either too light or two dark and the glasses all have very dark
> regions in them. Should I encase the whole thing in a box or sphere to
> increase the amount of ambient light?

As my learned colleagues have already mentioned the max trace level will
help here but what the glass object is refracting is also an important
element. The amount of ior specified will also contribute. Personally
I often add something outside the view of the camera to help give the
glass object(s) something else to refract besides the color black.

-- 
Ken Tyler -  1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Thank you very much for all the suggestions. You know, I love Pov-ing (my
girl friend does not though "you spend too much time doing that
stuff!".......), but there are a lot of things I still don't know.... :-)

Paul Daniel Jones wrote:

> howdy, I have two questions for you guys.
>
> 1) What is the best way to light a scene containing a lot of glass. ie:
> drinking glasses with liquid etc. I have tried multiple light sources
> (point lights and area lights) but just cant seem to get it right. The
> scene is either too light or two dark and the glasses all have very dark
> regions in them. Should I encase the whole thing in a box or sphere to
> increase the amount of ambient light?
>
> 2) This is a silly question of sorts, must you put a semi-colon at the
> end of a declare statment? I always forget to, especially in multi-line
> declares, and everything works fine for me.
>
> -paul

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On Fri, 03 Mar 2000 07:07:10 -0500, Paul Daniel Jones wrote:
>2) This is a silly question of sorts, must you put a semi-colon at the
>end of a declare statment? I always forget to, especially in multi-line
>declares, and everything works fine for me.

Only for numbers and vectors, if I remember correctly, and then you only
get a warning if you forget.  For now.

-- 
These are my opinions.  I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html

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Chris Huff wrote:
> 
> It is not required in the current version, but might be in a future
> version. You had better get in the habit now, while the only problem it
> causes is a warning.(if it happens in a loop, all those warnings can
> also slow parsing down)
> 

It _is_ required and can cause errors, although in most common cases it
doesn't. Macros can be picky about omitted semi-colons, and you can save
yourself a lot of headache by getting into the habit of using them.

Margus

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Paul Daniel Jones wrote:
> 
> 1) What is the best way to light a scene containing a lot of glass. ie:
> drinking glasses with liquid etc. I have tried multiple light sources
> (point lights and area lights) but just cant seem to get it right. The
> scene is either too light or two dark and the glasses all have very dark
> regions in them. Should I encase the whole thing in a box or sphere to
> increase the amount of ambient light?

Note that besides the possible max_trace_level problem, dark areas can
be caused by total internal reflection, i.e. the inside of the glass can
reflect a dark part of the scene (such as a black background)
Total internal reflection is a component of refraction calculations, it
is independent of the 'reflection' keyword and currently cannot be
turned off (anyway, the glass would usually look unrealistic without it)

Margus

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