Thanks. It is pretty close to what I want. Here is a beautiful image
demonstrating what I want to plot:
http://web.mit.edu/newsoffice/2003/smartsurface.html. Lots of chains were
grafted on a surface. They are rooted on the surface and grow upward
randomly. Any good suggestion?
Charles C <"nospam a nospam.com"> wrote:
> zj905 wrote:
> > I am doing some work on chemistry. The random coil looks like... It is
> > better to give a sample. Please see this picture:
> > http://www.psc.edu/science/Darden/bpti_spline_dense2.GIF. In this graph,
> > the white-yellow chains are random coils. How to draw that? Thanks.
>
>
> I typed something up but seeing this picture makes me think it might not
> be quite what you're looking for either.  (Looks like my lines are a
> little too long.) I'm posting it anyway in case it might still have some
> relevance:
>
> Charles
>
> //          /
> //****   o-/--   ************************
> //        o
>
> #include "colors.inc"
>
> global_settings {
>    assumed_gamma 1.0
> }
>
> camera {
>    location  <0.0, 0.5, -4.0>
>    direction 1.5*z
>    right     x*image_width/image_height
>    look_at   <0.0, 0.0,  0.0>
> }
>
> sky_sphere {
>    pigment {
>      gradient z
>      color_map {
>        [0.0 rgb <0.6,0.7,1.0>]
>        [0.7 rgb <0.0,0.1,0.8>]
>      }
>    }
> }
>
> light_source {
>    <0, 0, 0>            // light's position (translated below)
>    color rgb <1, 1, 1>  // light's color
>    translate <-30, 30, -30>
> }
>
> // ^^^^^ The above is modified from the POV-Ray for Windows insert menu
> ^^^^^
>
>
> #declare Wraps = 10;
> #declare BallRad = 1;
> #declare Increment_Val = 0.001;
> #declare Ctr = 0-Increment_Val;
> #declare MyRand = seed(0);
> #declare ThisRandVec = <rand(MyRand),rand(MyRand),rand(MyRand)>;
> //
> #declare MySpline =
> spline{cubic_spline
>    //Ctr,
> vrotate(<BallRad,0,0>,<rand(MyRand),rand(MyRand),rand(MyRand)>*360),
>    Ctr, vrotate(<BallRad,0,0>,ThisRandVec*360*Ctr*Wraps),
>    #declare Ctr = Ctr+Increment_Val; //now 0.... could'a just written 0.
>    #while(Ctr <= 1+Increment_Val)
>        //Ctr, vrotate(<1,0,0>,<rand(MyRand),rand(MyRand),rand(MyRand)>*360),
>          Ctr, vrotate(<BallRad,0,0>,ThisRandVec*360*Ctr*Wraps),
>        #declare Ctr = Ctr+Increment_Val;
>    #end //end while
> }//end spline
>
>
> #declare SphereRad = .01;
> #declare NumOfSpheres = 10000;
> #declare Ctr = 0;
> #declare A_Random_Coil =
> union{
>   #local Ctr = 0;
>   #while (Ctr <= 1)
>     sphere {
>       MySpline(Ctr),SphereRad
>       pigment { rgb <1-Ctr,Ctr,0> }
>       }
>     #local Ctr = Ctr + 1/NumOfSpheres;
>   #end
> } //end union
>
>
> #object{A_Random_Coil}
>
> //          /
> //****   o-/--   ************************
> //        o

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