Mapping hdr file to area light

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stefdln
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Mapping hdr file to area light

Post by stefdln » Tue Oct 23, 2018 5:06 pm

Hey everyone
I'm a newcomer to LuxCore and I appear to have a question
Is there a way to add a hdr or exr texture file to an area light to get more interesting lighting/reflections from these ?
This could be used to mimick softboxes for instance
Thanks in advance for your answer
Cheers

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B.Y.O.B.
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Re: Mapping hdr file to area light

Post by B.Y.O.B. » Tue Oct 23, 2018 5:22 pm

Yes, but you will have to use a plane object with material nodes.
The Blender area light is just a shortcut for this, internally it works the same.
Any material can emit light.

Then just create a UV map for the plane and set up the material:
(remember to set gamma to 1 on the image node, most HDR images have gamma 1 instead of 2.2)
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stefdln
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Re: Mapping hdr file to area light

Post by stefdln » Tue Oct 23, 2018 6:00 pm

Thanks a lot for the answer
I guess Multiple Importance Sampling work with this type of setup too ?

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B.Y.O.B.
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Re: Mapping hdr file to area light

Post by B.Y.O.B. » Tue Oct 23, 2018 6:18 pm

To be honest, no idea.
You mean that brighter parts of the area light are sampled with higher probability than dark parts?
Dade, do triangle lights use MIS?
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stefdln
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Re: Mapping hdr file to area light

Post by stefdln » Tue Oct 23, 2018 6:22 pm

That's exactly what I mean yes

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Dade
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Re: Mapping hdr file to area light

Post by Dade » Tue Oct 23, 2018 6:27 pm

A projection light source may be also what you are looking for, it depends on what you are trying to achieve. It is like the light emitted by a TV screen Vs. the light emitted by a movie theater projector.
B.Y.O.B. wrote:
Tue Oct 23, 2018 6:18 pm
Dade, do triangle lights use MIS?
I think he is confusing MIS and (Multile Importance sampling) just IS (Importance sampling). LuxCore always uses MIS for any intersectable light source (because you have multiple way to receive light from the light source).

However it uses Importance sampling for infinite light sources (HDR light source) but not for a light source with a texture applied. IS means you sample more the brighter area of the image.
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stefdln
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Re: Mapping hdr file to area light

Post by stefdln » Tue Oct 23, 2018 6:30 pm

Thanks for clarifying that point

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