Le 2019-12-20 à 20:31, AndreyG a écrit :
> I image wood textured surface covered with glass.
> Camera positioned perpendicular to imaged surface
> Illumination done using Parallel light source.
> Light falls perpendicular to imaged surface.
> When there is no glass camera shows image with uniformal brightness across the
> field – what I would expect.
> When image overlaid with glass camera depicts bright spot right in the centre of
> the image.
> As it is shown here:
> https://imgur.com/a/xzflV2T
> 
> What causes bright spot? Is it reflection of light source? But there is no
> source, all light rays a parallel and fall perpendicularly to the surface. What
> causes bright spot?
> 
> 

The finish of your glass have specular of phong highlight enabled.
The light is still a point, it's just that the light it emit is assumed 
to always have the same direction.

You can shift the light so that the highlight is outside the visible 
area, or remove the phong or specular components from the finish.



Alain

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