"flashlight" example and docs

[rpavlik]

@jane-peters - I think this would be a good one for you.

[jane-peters]

As per Ryan's suggestion, here is an example of how I created the "flashlight effect".

https://gist.github.com/a91bc1880f2aa3c65adb

It is pretty easy to modify in terms of brightness, beam radius, ect.

[rpavlik]

Can you work with leif to trim this down to the minimum useful and add comments as to how you might want to change values (and which to not change)

[jane-peters]

I do believe it is more 'bare-bones' now.

[rpavlik]

Ah, very nice! Didn't realize you had updated it. A few little comments:

• May want to mention that the top "get or create state set" means that the light will be applied for all children of that node, unless overridden.
• Also, explain that where you attach the "lightsource" determines the position and orientation of the light only (not what nodes it affects).
• Also perhaps mention that it's convenient to add a single sphere as child of the lightsource to show the location the light comes from?
• make variables local, and perhaps name them more like myLight instead of light1 (since by default it's actually using OpenGL's light 0 slot)
• Maybe also load a model that shows lighting well - I know @lpberg used the basic factory.

Perhaps some of these actually suggest that there should be multiple examples - first one like this, then one with a sphere at the light source, or maybe a set of axes. Nice work! Please work with Leif to get this good to go and in - and poke him about the two pull requests he made that I touched up and re-submitted: one of them is for lighting which would give you a place to put this, and I want to make sure I'm representing what he did correctly before merging it.