> Rune wrote:
>> 
>> "Joshua English" wrote:
>> > After the are light keyword you can input two vectors,
>> > they don't have to be strictly along the x and z axis,
>> > so you can use <0,0,4> and <0,1,4> and it will create
>> > the two rows of lights oriented along those paths.
>> 
>> I know how a regular area_light works. What I'd like to know is how it is
>> oriented when the orient keyword in MegaPov is used. Especially if the
>> area_light is rectangular.
>> 

> Using the "orient" keyword, the area_light shape remains unmodified,
> but whenever a ray is computed to this light source, the area is 
> made orthogonal to this ray (rotation about the center of the area,
> you cannot specify the angles to use/fix).
> It's hack to have a kind of quick volumetric light

Right, but what's the axis of rotation?  if the area light is non uniform,
this makes a difference.  Ie, if we have an area light that's twice as wide
as tall, and a point that's perpendicular to its normal, do we get a small
square or a big square, or something in between?  When the area light is
uniform, it's obvious what it does, when the axes are of different lengths,
it isn't clear what the shape of the light appears to be when looked at from
a particular object.

The obvious axes of rotate are the axes of the area light itself, but again,
how much of each is used, and which is first (if, indeed, those are the axes
used, which is non-obvious)?  Because the shape of the light is affected
greatly by the order and magnitude of these rotations.

Geoff

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