Model a collimated light source

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Model a collimated light source

Postby nyorem » Wed Sep 27, 2017 1:12 am

Hello,

For my project, I need to model an ideal collimated light source meaning a light source that emits parallel rays (see: https://en.wikipedia.org/wiki/Collimated_light).
I already tried to use the following methods:
- use an area light (with a square mesh) with an IES profile of a laser (found here: viewtopic.php?f=36&t=6485#p66844),
- place a spotlight far away from my scene and put a cache inbetween to filter the incoming light rays.
But the results are not so good.

I saw that LuxCore supports laser like light sources but I would like to use the Classic API.
Does anyone know how to do that?

Thank you.
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Re: Model a collimated light source

Postby Piita » Wed Oct 04, 2017 8:53 am

You could try this one: http://jamiecardoso-mentalray.blogspot. ... s-for.html

I've used the same program but I cannot say if you can create ies profiles with parallel rays with it.
The laser profile you mentioned is very cool but I just noticed it does spread the beams a little bit.
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Re: Model a collimated light source

Postby nyorem » Thu Oct 05, 2017 10:08 am

Thanks for the answer.

Indeed, I already looked at that and I didn't manage to create perfect parallel rays with it, the beams seem to always spread.
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Re: Model a collimated light source

Postby jantschek » Fri Oct 06, 2017 5:53 am

Hi,

I'm afraid it's impossible to model perfect parallel beam with IES files. This IES type is made to describe the spread of a luminaire. At least a little spread will remain even while using tinyest angular resolution.

Have you thought about using a point light source and a collimating reflector or lens to create parallel beam.

If you like to tell me some details of your project I could try to model such geometry for you.

BR
Lux Render Version: 1.7 (in classic mode)
Exporter: Blender
Exporter Version: 2.79
Operating System: Windows 7 X64
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Re: Model a collimated light source

Postby Piita » Fri Oct 06, 2017 12:26 pm

The sun lamp can create quite parallel rays if you make the sun smaller but I'm not sure if this is accurate enough for your setup. This setup here uses a sun lamp size of 0.0001 and a room with a square hole + long pipe at the top, letting a limited amount of rays through. See blend file. The color and brightness of the sun is determined by its rotation so you probably need to keep it pointed straight down and flip the rest of the objects in your scene instead.
Path can't render this. But bidir can, because bidir is awesome :)

parallell rays test2.blend
(579.81 KiB) Downloaded 62 times


parallell_rays_test2.jpg
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Re: Model a collimated light source

Postby jantschek » Sat Oct 07, 2017 11:51 am

Hello,

this is my attempt on generating parallel beam:
As described it's a collimating lens (based on n=1.5 and focal length 20mm).
The image is generated while using to plain mirrors and a matte sphere in a slightly scattering volume to makt the beam visible.

Collimated_Light_Source.jpg
Sample rendering result


This is the used *.blend file.

Collimator.blend
Sample file
(1.66 MiB) Downloaded 96 times


BR
Lux Render Version: 1.7 (in classic mode)
Exporter: Blender
Exporter Version: 2.79
Operating System: Windows 7 X64
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Re: Model a collimated light source

Postby B.Y.O.B. » Sun Oct 08, 2017 5:54 am

Piita wrote:The sun lamp can create quite parallel rays if you make the sun smaller

The rays from the sun lamp are always parallel, the size does not matter (bigger size just makes shadows softer, rays remain parallel). Just a side note.
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Re: Model a collimated light source

Postby nyorem » Mon Oct 09, 2017 2:04 am

Thanks for the really interesting answers!

jantschek's setup seems to be exactly what I need.
Can I ask you which method you used to build such lens?
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Re: Model a collimated light source

Postby jantschek » Tue Oct 10, 2017 7:07 am

Hi...

The methode to define a collimating lens is simply the application of Snell's law for refraction. I did it in a CAD software and exported the result geometry as high resolution stl file.

Do you have the chance to do it on your own?
If you let me know the boundary conditions of project I could try to support you.

BR
Lux Render Version: 1.7 (in classic mode)
Exporter: Blender
Exporter Version: 2.79
Operating System: Windows 7 X64
jantschek
 
Posts: 194
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Re: Model a collimated light source

Postby nyorem » Wed Oct 11, 2017 7:11 am

Ok, it seems doable, I'll try to do it by myself.
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