Danny nous apporta ses lumieres ainsi en ce 2004/05/21 16:22... :

> <snip>
>
>
>Is this cylinder light_source supposed to produce a visible light beam that
>can be seen outside where it's pointing at, or is it more like a laser pen
>that produces a dot on the surface it's aimed at? I tried it along with
>scattering and it did nothing to get rid of the images.
>Also, in order to round off the ends of my laser beam, I put some
>half-spheres on either end, both filled with the same media, except the
>density is spherical instead of cylindrical.  For some reason, this created
>tons more problems.  When you look at the half-spheres perpendicularly,
>there's no problem, but when you look at them obliquely, you get very odd
>results, such as grey rings, spots, etc.  Here's what I'm doing:
>
>  
>
Why do you use this default texture, it's the source of most of your 
problems

> #default {
>   texture {
>  pigment {Grey}
>    finish {
>     diffuse 0.6
>      ior 1.5
>      ambient 0.300000
>      phong 0.5
>      phong_size 50
>}
>}}
>
>
>camera {
>  location <0,0.5,2>
>  look_at <0,0.5,0>
>}
>
>background {color rgb <0,0,0>}
>
>light_source {
>  <-1000.000000,1000.000000,1000.000000>       //  x=-1000,y=1000,z=1000
>  color rgb <1.0000,1.0000,1.0000>
>           }
>
>#declare clock1=1;
>
>union{
>cylinder{<0,2*clock1,0>,<0,0,0>, 1                 //the laser, top right
>from front
>         texture {
>    pigment { color rgbt 1}}
>       interior{media{emission rgb 1
>       density{ cylindrical
>       color_map{[0 rgb 0][0.03 rgb <0.0004,0,0>][0.6 rgb<8,0,0>][0.98 rgb
>16][1 rgb 30]} //[0 rgb 0][0.02 rgb <0.004,0,0>][0.5 rgb<4,0,0>][0.96 rgb
>5][1 rgb 10]
>       }}}
>       hollow
>       scale<0.1, 1, 0.1>
>       }
>  
>
removing this don't change anything in your cene

>difference{
>sphere{<0,0,0>, 1
>         texture {
>    pigment { color rgbt 1}}
>       interior{media{emission rgb 1
>       scattering{3,1}
>       density{ spherical
>       color_map{[0 rgb 0][0.03 rgb <0.0004,0,0>][0.6 rgb<8,0,0>][0.98 rgb
>16][1 rgb 30]}
>       }}}
>       hollow
>       scale<0.1, 0.1, 0.1>
>       translate <0,2*clock1,0>
>       }
>cylinder{<0,2*clock1,0>,<0,0,0>,5}
>       }
>  
>
-----------------------------------------------------------------

>difference{
>sphere{<0,0,0>, 1
>         texture {
>    pigment { color rgbt 1}}
>       interior{media{emission rgb 1
>       density{ spherical
>       color_map{[0 rgb 0][0.03 rgb <0.0004,0,0>][0.6 rgb<8,0,0>][0.98 rgb
>16][1 rgb 30]}
>       }}}
>       hollow
>       scale<0.1, 0.1, 0.1>
>       }
>cylinder{<0,5,0>,<0,0,0>,5}
>        }
>light_source{0 rgb 10 cylinder point_at y*2}
>}
>
>sphere{<.2,.5,-.5>,0.1}
>
>
>Try running this and you'll see the image of the sphere on the laser.
>  
>
Default ior applied to the cylinder

>You'll also see the grey ring where the laser cylinder and the laser
>half-sphere meet(try looking at that location perpendicularly and the grey
>ring disappears).
>  
>
Default texture applied to the substracting cylinder

>You can also see a small white dot on the bottom half-sphere, which is also
>an image of the grey sphere. 
>
Default texture's ior again

> I have a background of stars, and so the ends
>of my laser end up looking speckled.  How can I make all those images and
>grey rings go away?
>
>  
>
1- Remove the ior statement in your default. Thin add an ior to your 
cylinder, this is what cause the sphere to apears in your beam.
2- Use merge instead on an union. This will remove the internal surfaces.
3- Use difference{sphere{...}cylinder{...}texture{...}interior{...}}. 
That is, apply the texture and interior to the whole 
union/difference/intersection/merge. The cylinder get the default 
texture and apply it to where it intercect the sphere, giving you that 
gray circle.

Alain

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