> If you add filter_all to the image, it makes it transparent.
> Alternatively, you can use a PNG with an alpha channel. You should
> experiment to fing the best alpha value for your case. Do your tests for
> a single "typical" frame.
> Then, you add a normal point_light, possibly as a spot_light, behind the
> "slide". Be sure to put a frame around your image to block any extra light.

Thanks - Sounds like exactly what I need. I'd prefer to avoid Alpha-PNG 
if possible - it would be better if I could do all the without 
pre-processing the frames I get (currently BMPs - Good job I recently 
got a new HDD)

>
> If there is anything between the slide and the screen, it's shadow will
> be visible, and that thing will get illuminated.
>
Excellent

> In that setup, there is no actual lense in your projector. Only an
> absolutely punctual light_source and a slide/film. The image will be in
> focus everywhere, not just on the screen.
> If the "room" contains a light scattering media, then, that media will
> show the projected beam.
Fade distance is a good point, as is a lens - Is there any reason why I 
can't scale the image down, then use a lens with the appropriate steup 
to "project" the light? Or am I now moving into the realm of photons?

> You may want to have the light's intensity change as a function of the
> distance from the projector. For that, you need to use fade_power 2 and
> fade_distance <something> for your light_source. The intensity of your
> light should be increased to compensate the fading. In some cases, a
> value of rgb 100 or even more can be required for the light_source.
>
> For the smoke, you should use some media. If the media itself is not
> visible, but only it's effect is, then you should use an absorbing media.
> If the "smoke" is to be visible, then you need to use scattering madia.
>
>
> Alain

Thanks :)

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