how to modify light "power and color" after rendering

Practical and theoretical implementation discussion.
MohamedSakr
Posts: 83
Joined: Thu Apr 24, 2014 2:27 am

Re: how to modify light "power and color" after rendering

Postby MohamedSakr » Sun Aug 10, 2014 9:48 pm

@yuriks I understand :D , and thanks for the example

but why it is wasteful? I think it is a just a single operation per lightGroup!!
so when you trace, you will just create multiple buffers and store each one alone, then sum them at the end of each iteration, I see it is kinda a few flops (just the addition flops for each light group) and the memory usage, I think there is no need to re-render

yuriks
Posts: 7
Joined: Fri Jul 25, 2014 1:22 am

Re: how to modify light "power and color" after rendering

Postby yuriks » Sun Aug 10, 2014 11:50 pm

If you re-render the whole image then you have the overhead of creating paths, tracing rays, sampling, calculating cosines, etc. which doesn't really vary by light but that's still being repeated anyway. If you use the light-vector approach then that's only computed once and you save on that computation. So what I mean is that yeah, it's faster using the light vector (which is equivalent to multiple buffers).

MohamedSakr
Posts: 83
Joined: Thu Apr 24, 2014 2:27 am

Re: how to modify light "power and color" after rendering

Postby MohamedSakr » Wed Aug 13, 2014 1:19 pm

what about camera parameters? like ISO

Dade
Posts: 206
Joined: Fri Dec 02, 2011 8:00 am

Re: how to modify light "power and color" after rendering

Postby Dade » Thu Aug 14, 2014 7:17 am

MohamedSakr wrote:what about camera parameters? like ISO


If you mean tone mapping (like film sensitive), it is done after the merging so it is not a problem. It is not even part of the rendering process (for instance, save in .exr and than apply to the file any kind of tone mapping you want).

MohamedSakr
Posts: 83
Joined: Thu Apr 24, 2014 2:27 am

Re: how to modify light "power and color" after rendering

Postby MohamedSakr » Thu Aug 14, 2014 8:12 am

I see, I will check more about cameras soon :)
thanks a lot Dade


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