Looking for Tutorial: Iray Photometric light geometry

Scavenger

I'm trying som iray conversions of old sets, and I think what i want to do will be helped with using photometric point lights, but I need to learn more about them, specifically the geometry control(s).  Can anyone point me to some tutorials/videos/exercises that might fill me in with what I'm looking for?

(I'm at the point where I can't even ask a specifc question other than "what's geometry", which is why this is so vague)

Szark

Light Geometry, as far as I can make out, is having the ability to change the shape and size of the light.  You can use Render Emitter to control if the shape is visible in the render but you will always get the shape in reflections no matter if Render Emitter is on or off.

 

The light will be the same whether the emitter is shown or not. Changing the shape does change how light is emitted.

 

I took a screencap so you can see the point light and the shape that I dialed in.

Scavenger

Shouldn't a bar shine a different light than a point?

Szark

yes and it does, ok it doesn't show it my example very well but from what I have done with adjusting shape size s in the past year has proven to me that it works the same as a mesh light

fastbike1

It works like a mesh light but it much faster calculate. The effects of geometry should be thought of in terms of a photographic softbox. Just bear in mind that the units are cm.

Scavenger

fastbike1 said:

It works like a mesh light but it much faster calculate. The effects of geometry should be thought of in terms of a photographic softbox. Just bear in mind that the units are cm.

I recognize that these are words, but I have no idea what any of this means in combination :)

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I've done some experiments, and what I've found is that for a given luminence setting, geometry controls how the ammount of light is distributed.

So, a column at lum: 500 looks "brighter" at  width 10 than at width 100.  The light is still putting out 500 lumens into the scene, but because they're spread out, they're not as "bright".

I assume there's some kind of formula that could be figured for size to lumen to brightness.

Szark

Scavenger said:

fastbike1 said:

I assume there's some kind of formula that could be figured for size to lumen to brightness.

I so wish there was as I haven't found one yet