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Different light behavior comparing Preview to Final Render

Posted: Fri Sep 25, 2020 9:58 pm
by Leandro Oliveira
Hi everybody.

Why this is happen? Lights in preview render are so different from final render.

Preview
Preview.JPG
Final
Render.JPG

Re: Different light behavior comparing Preview to Final Render

Posted: Fri Sep 25, 2020 11:37 pm
by Sharlybg
Maybe a light is off rendered for final. But can be solething else. We do need the actual scene ( simple version of the scene).

Re: Different light behavior comparing Preview to Final Render

Posted: Fri Sep 25, 2020 11:50 pm
by Leandro Oliveira
Sharly, are caches view dependent? Because I tried to generate caches from this view (original caches were computed from the living room) and it returned a different look.

I´ll send you the scene.

Add cache location
new cache.JPG

Re: Different light behavior comparing Preview to Final Render

Posted: Fri Sep 25, 2020 11:58 pm
by Leandro Oliveira
Shaly, I´ve sent you the scene. See your private messages.

Thanks.

Re: Different light behavior comparing Preview to Final Render

Posted: Sat Sep 26, 2020 10:41 am
by Dade
Leandro Oliveira wrote:
Fri Sep 25, 2020 9:58 pm
Why this is happen? Lights in preview render are so different from final render.
During viewport rendering, caches are disabled (in order to avoid pre-processing time) and the default number of light bounces is reduced (to increase rendering speed). This may produce a darker rendering if you have a lot of indirect light.

This may explain your problem.
Leandro Oliveira wrote:
Fri Sep 25, 2020 9:58 pm
are caches view dependent?
Cache entries are view independent but the number and the position of cache entries is based on the camera used to create the cache.

The very first step of cache creation is to fire "visibility particles" and mark places where they bounce (4 max. bounces is the default setting). The cache entries are create there and only there.

If you have a building with 100 rooms, the cache will be created for the room where the camera is and for near rooms reachable in 4 bounces. Far you are from the original room and less likely the surfaces have cache entries.

So if you are doing an animation inside the same room, you can reuse the cache, if you move across many rooms, you need to update the cache.

Re: Different light behavior comparing Preview to Final Render

Posted: Sat Sep 26, 2020 10:45 am
by B.Y.O.B.
Dade wrote:
Sat Sep 26, 2020 10:41 am
and the default number of light bounces is reduced (to increase rendering speed)
Not in the Blender addon, as far as I know.

Re: Different light behavior comparing Preview to Final Render

Posted: Sat Sep 26, 2020 1:24 pm
by Leandro Oliveira
Dade, that´s it! I have to update cache, because I have other rooms. Thanks a lot!

I forgot to mention that I´m using Blender 2.83.6 and Lux 2.4.

And about BYOB observation?

Re: Different light behavior comparing Preview to Final Render

Posted: Sun Sep 27, 2020 2:48 am
by Leandro Oliveira
Another question: light rays emitted from mesh lights are considered indirect light?

Re: Different light behavior comparing Preview to Final Render

Posted: Sun Sep 27, 2020 11:56 am
by Dade
Leandro Oliveira wrote:
Sun Sep 27, 2020 2:48 am
Another question: light rays emitted from mesh lights are considered indirect light?
Only after > 1 bounces.

Re: Different light behavior comparing Preview to Final Render

Posted: Sun Sep 27, 2020 12:50 pm
by Leandro Oliveira
Thank you, Dade!