Challenging Snell's Law: Light Deviation Anomaly in LuxCore Glass Rendering

[LensCraft]

I have created a scene based on the image below. A spotlight illuminates a glass slab with a refractive index of n and strikes a translucent screen. Below the screen, an orthographic camera is positioned to capture images for different values of the refractive index. One would expect the position of the beam to hit the translucent screen at different positions, according to Snell's law, when n is varied; however, this is not the case, as can be seen in the captured images.

Am I approaching this the wrong way? Can anyone shed some light on this anomaly?

I'm using Blender 3.6.5. LTS and LuxCoreRender 2.7

[kintuX]

With PT engine (uniDir) you should enable "Light Tracing" under Light Path otherwise, switch engine to BiDir.

e.g.

PS.
If you still find your scene non-functional, make it as IRL, physically correct;
I made new scene and used Area light and also Interior + Exterior volumes.

[LensCraft]

I followed the suggestion and turned on Light Tracing, and indeed, a spot appears on the screen that corresponds to a beam deviating according to Snell's law. But that is not all. Three more spots appear; one spot has its nature in a light beam that is unaffected by the glass slab. The other two spots are a bit more mysterious.

In an attempt to understand this better, I placed the experiment in a fog chamber. The result is somewhat unexpected: the beams interacting with the glass slab are not visible. I show this in the attached image, and I attach the blend file.

It would be super interesting to hear if anyone can explain why this happens, i.e., why are the beams interacting with the glass slide invisible? Is it possible to configure LuxCore to make the beams visible?

Illustration of problem

Viewport

The blend file is a bit over 2 MB, and I therefore share it through GoggleDrive

https://drive.google.com/file/d/1DdexXT ... sp=sharing