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I'm trying to create a proper physics based laser beam. Therefore I have chosen to have a look into geometry nodes, outline the laser path with a bezier curve (it is going to be reflected on mirrors by 90 degree angles) and profile the laser beam with a circle. I'm facing two problems (I'm new to geometry nodes, sorry for stupid questions)

  1. The diameter in front of the 90 degree angle changes, which is unphysical. (as of my understanding, this happens, to keep the cross section from the outer edge to the inner edge) How to tell blender, that the diameter on a straight line should be as stated? (The Bezier curve spline type is set to Bezier, the handle types of the 4 defining edges are set to vector. Including points made matters worse, resampling the curve aswell) enter image description here

(Later on, the diameter of the curve has to be a function of the curve parameter to follow the cross section of a physical based gaussian laser beam, but this should be easy)

This problem is additionally arising, when animating the laser propagation via the trim curve parameter: changing diameter when triming the curve

  1. As the laser is focused and the same amount of light is passing each crosssection the amount ambient illumination should be constant along the path as well as the apparent brightness of the beam should be increased. As the emitting volume decreases along the curve, the emission strength has to increased as a function of the curve parameter. Unfortunately I was not able to pass the curve parameter into the strength value of the emission shader. How is this achievable?

light falloff along the curve

Max Hacki
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  • https://blender.stackexchange.com/questions/56079/how-can-i-make-a-perfect-sweep-with-bevel-object-in-bezier-curve3d-pipe https://blender.stackexchange.com/questions/66353/how-to-make-beveled-90-degree-corners-on-a-curve-better – Duarte Farrajota Ramos Dec 12 '21 at 16:38
  • Thanks, but this does not the job, as I need sharp edges and not a curved version (as this represents a light beam and at the edges, it's actually reflected on a mirror, rather than "bent around") ... and sadly I was not able to use any information in these links to tackle the triming problem and the shading problem :/ – Max Hacki Dec 12 '21 at 16:54

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