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[ISSUES] Strange Area Lights

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[ISSUES] Strange Area Lights

Unread postby grabiller » Thu Aug 01, 2013 7:06 pm


I am a bit puzzled by my experimentations with area lights.

Here is a scene with 2 area-light, one on top (you can clearly see the white area) and one on the left (you can see its influence but the case material react as black).

There are several issues here:

1) We don't 'see' the area lights areas. Is there an option somewhere to actualy 'see' the area lights areas without ressorting to a luminous surface ?

2) This one may be not related to area lights but is definitely strange: The area lights 'supports' (rectangular geometry behind each area light) have both the exact same material (same instance), and the one at the top is properly illuminated by the top area light as we can see on the image, but the one on the left stays completely black. I did not used any light/object/surface link.

3) This is the one that worries me the most: As soon as I add a gi_monte_carlo into the context, I get lots of fireflies:

Sampling is 6 on the raytracer, 6 for both area lights and 6 for gi_monte_carlo.
Top area light intensity is 8, left is 2.

The room is a closed cube with no hole.

Am I doing something wrong here ? Are they any known issues about this kind of setup ?

guy rabiller | | radfac founder/ceo
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Re: [ISSUES] Strange Area Lights

Unread postby isoyann » Mon Aug 05, 2013 11:08 am

1) Currently, no... This is planned for future versions, but currently you must parent a polygrid to your light, set with "cast shadows", "receive shadows", and "is emmiter" to off, with a matte matterial set to the light color.

2) Maybe the light is just behind the object? Did you try to move it a little?

3)This is cause by extreme values on the surface just behind the light. The default physical light fallof use an inverse distance exponential, so objects very close to the light receive lots of light in a small area, causing this problem in indirect lighting (this is a very common issues in all raytracers.. ). Attaching grid to lights (like explianed in 1) ) , hiding the extreme values to the GI, solve the problem. Here is an example using your quality settings, with and without cards :

nocards par isoyann, sur Flickr

cards par isoyann, sur Flickr

We'll add in future an option to emit rays from area lights in only one direction.. it will solve this problem in a more simple way..
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