On 12/5/25 09:51, radmac wrote:
> How does one create perfect mirror to reflect beam of light in scattering media?
> In attached scene, the reflected beam is clearly different from the incident
> one.

In your posted scene, mostly, what is causing the difference in 
intensity is that the beam for the light source to the mirror path is 
being calculated by the scattering media mechanism, while the reflected 
beam is being calculated by the photon mechanism.

Attached a modified version of your posted scene and four images (No 
AA). The scene has been updated to calculate both paths light intensity 
with the photon mechanism. For all changes look for '***'.

In the attached image the left column is POV-Ray version 3.8 beta 2; The 
right column is my yuqk fork - which has a fix for the photon banding.

The top row has 'media_interaction on' for the beam light - with the 
photons now used for both paths, the difference in intensity between 
paths due the scattering component is even more apparent. The bottom row 
turns 'media_interaction off' for the beam light - both beam path 
segments are now calculated solely by the photon mechanism.

Bill P.

Aside: The general rule with light sources and media is that the light 
source should be outside any media container by some small value.

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Attachments:
Download 'radmacphotonbeam_story.png' (110 KB) Download 'radmacphotonbeam.pov.txt' (2 KB)

Preview of image 'radmacphotonbeam_story.png'