"AndreyG" <nomail@nomail> wrote:

> Thank you for your comments, this might be of interest only if I manage to model
> physically realistic optical scenes. According to laws on physics, geometrical
> optics in particular.

All I'm saying is that the documentation states certain things about the
behaviour of a spotlight.
Whenever I use a feature and it doesn't do what I expect it to do, I:

Re-read the docs
Model the thing on my own to compare my interpretation with the POV-Ray
implementation
and then try to describe in detail what the problem is

Sometimes, even now, things in the POV-Ray source code still aren't correct.
http://news.povray.org/povray.beta-test.binaries/thread/%3C5daec47c%241%40news.povray.org%3E/

I usually wind up answering my own questions 75% of the time when I start
writing a detailed request for help.


> So far it does not look like it maybe because I am not using it correctly?

I'm not sure - the other thing to do is run a search and see if there are any
other scenes with spotlights that might give a clue.  Sometimes "3rd party"
websites have interesting scenes / blogs / tutorials that are clearer or more
complete.

> If I specify beamwidth of certain angle it should result in spot of light of
> certain size at certain distance. If angle is changes size of the light spot
> should change.
>
> So far I do not see it in my models.

The other thing to do in order to visualize the light source is just add a
vertical "wall" very close to the plane of the spotlight for the cone of light
to shine down along.

As a last resort, sometimes I try to hunt down the section where the feature is
implemented in source code so I can see _exactly_ how it's implemented - I'd
probably look at 3.6 or earlier to start with, as 3.7/3.8 can be really hard to
follow.

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