Hi,

I would like to draw laser rays. In my project, they are always in a given
plane, so I try to add a thin invisible object around this plane, with an
interior defining scattering. I can visualize the laser rays, and of course, as
expected, if an object comes in front of it, the ray is stopped by the object.
But my problem is that I don't find any way for thsi object to be invisible. A
small piece of code allowing to reproduce my problem is the following. Does
someone know how I could modify it to make the plane invisible while still
seeing the rays ?

#include "colors.inc"

global_settings {
    ambient_light rgb < 1 , 1 , 1 >
    max_trace_level 15
    photons {
        count 100000
        autostop 0
        jitter .4
        media 100
    }
}

camera {
    perspective
    up < 0 , 0 , 1 >
    right y * image_width / image_height
    location < 0 , -20 , 2.5 >
    look_at < 0 , 0 , 0.8 >
    angle 40 // horizontal FOV angle
}

background { Quartz }

// a laser ray

#declare ray_radius = 0.01 ;
light_source {
    < 0 , 0 , 0 >
    color rgb 100 * < 1 , 0 , 0 >
    cylinder
    point_at < 1 , 0 , 0 >
    radius ray_radius
    falloff ray_radius
    tightness 0
}

// virtual plane needed to observe the laser rays

#declare dx = 13 ;
#declare dy = 6 ;
box {
    < - dx / 2 , - dy / 2 , - ray_radius > < dx / 2 , dy / 2 , ray_radius >
    material {
        texture {
            pigment { Clear }
        }
        interior {
            media {
                scattering {
                    1 /* isotropic */ , rgb 5 * < 1 , 1 , 1 >
                }
            }
        }
    }
    photons { pass_through }
    hollow
}

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