POV-Ray : Newsgroups : povray.general : How to get the light intenity that hits a surface? : Re: How to get the light intenity that hits a surface? Server Time
7 Dec 2021 17:33:17 EST (-0500)
  Re: How to get the light intenity that hits a surface?  
From: Alain Martel
Date: 16 Jul 2021 11:59:46
Message: <60f1acf2$1@news.povray.org>

> Hi,
> I would like to mis-use POVRAY (or any other tool) a bit to get to the light
> intensity that hits a surface of an object.
> The original problem comes from design questions of a photocatalyst, where the
> incident photons cause a chemical reaction.
> So my thinking goes like this: I can construct a scene with the geometry that
> holds my catalyst (usually some sort of 3D-grid, mostly cubic), edit the surface
> properties of the catalyst in terms of
> reflectivity, add a light source and let POVRAY calculate the scene.
> What I obviously get is an image of the scene as seen from the camera.
> Is there a way to get the intensity of light that hits surfaces that the camera
> does not see in such a scene? And then get it in such a way that it can be
> evaluated, lets say via ImageJ?
> Thanks for any hints!
Get the intensity of the illumination for part that are out of view ?
Unless you see something, directly or in reflection/refraction, the 
intensity of light reaching it is not computed as it don't need to be.
In a radiosity scene, those surfaces are often evaluated,

What you can do is to use an animation where the camera orbits your 
scene. That way, by combining the images, you may get what you want. 
Just not from a single image.

Add :

rotate y*clock*360

at the end of the definition of your camera.
You may want to rotate around another axis. In that case, just replace 

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