[Bf-cycles] Zero-Angled Spotlight?

[Sergey Sharybin]

I'm not sure what exactly spread angle means in this context, you already
have it for spot lights and adding spread angle to spot and sun lights is
somewhat malformed.

What we can do instead is either of:

- Modify energy function of area light, so it only contributes light inside
of a beam defined by it's area. Should be quite quick hack, but would
require some tweaks to PDF to make MIS working correct. Also circular
lasers can not be supported by this. This seems exactly what Lux does
(maybe internally they actually switching from rectangle to circle tho).
- Make spot light's source non-zero. Effectively making it to shoot
cylinder instead of a cone.

We can also go totally crazy ans support Laser option for any object, so
even meshes with emission shader can be acting as lasers, making it
possible to use laser beam of arbitrary shape.

On Wed, Sep 2, 2015 at 12:56 PM, Mohamed Sakr <3dsakr at gmail.com> wrote:

> Hey Sergey,
>
> I guess we can add a spread angle parameter to lights? "hemisphere cone"
>
> On Tue, Sep 1, 2015 at 5:03 PM, Constantin Rahn <conz at vrchannel.de> wrote:
>
>>
>> It's not possible with cycles, but it's available in Luxrender 1.4+ and
>> an area light with "laser on".
>> http://www.luxrender.net/forum/viewtopic.php?f=16&t=11572
>>
>> http://www.luxrender.net/forum/viewtopic.php?f=12&t=11533
>> "- add constantinfinite, laser lights"
>>
>> Sorry for pointing to other FOS software in the cycles ML. ;)
>>
>>
>> Am 01.09.2015 um 16:51 schrieb Zauber Paracelsus:
>> > The problem with that, however, is that the laser would be visible when
>> > it is not passing through the mist as well.
>> >
>> >
>> >
>> > On 09/01/2015 10:48 AM, Mohamed Sakr wrote:
>> >> actually this is not possible with lights, your only solution is a
>> >> cylinder object "acting as your laser light" , and put an emission
>> >> node in the volume output "leave surface empty"
>> >>
>> >> On Tue, Sep 1, 2015 at 4:42 PM, Zauber Paracelsus <zauber at gridmail.org
>> >> <mailto:zauber at gridmail.org>> wrote:
>> >>
>> >>     Would it be possible to change the minimum angle width of a
>> spotlight
>> >>     from one degree to zero?  I was tinkering with a scene filled with
>> >>     mist,
>> >>     and wanted to create the effect of laser lights transmitting
>> through
>> >>     mist, which would scatter their light and make the beam visible.
>> The
>> >>     closest light I could think of that would produce the effect was a
>> >>     spotlight, but due to its minimum angle width of 1 degree, I am
>> >>     not sure
>> >>     if I can accomplish the effect.
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>> >>
>> >>
>> >>
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-- 
With best regards, Sergey Sharybin
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