On 15/12/2017 16:05, clipka wrote:
> Am 15.12.2017 um 16:40 schrieb Stephen:
>> On 15/12/2017 15:08, William F Pokorny wrote:
>>> I know of no built in way to strictly get a conical light source where
>>> all the rays are at 45 degrees relative to some light source axis.
>>
>> I thought you could but I can't get it to work.
> 
> It's not possible to limit the light source to rays at /exactly/ 45
> degrees, as that would be an infinitesimally thin cone, and the
> raytracing algorithm wouldn't catch any of the light (except by mere
> coincidence).
> 

Muddled thinking on my part.

> To limit the light to, say, between 40 to 50 degrees, you could create a
> spotlight with a 50 degree angle, and another spotlight with a 40 degree
> angle and /negative/ brightness.
> 
> However, using a point light and a torus as a `projected_through` object
> /should/ also work in principle.
> 

It does, it gives a disk like beam. The code I posted on the duplicate 
of this thread shows that.
But it did not until I rotated the the light source by 180°. Rotating it 
by less than that makes it behave as if you are rotating a torch. It 
gives an elliptical beam.

That puzzles me as it was a point source.

-- 

Regards
     Stephen

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