MrLoft nous apporta ses lumieres en ce 2007/11/08 07:19:
> Hi everyone,
> 
> I wish to make a plane with random drops of water.
> The random insue is about translating drops and scalind them.
> 
> I'm a 'rookie' and I've reached so far by reading documentation,
> but I can't go any further.
> 
> Random translating is ok, but I can't change the shape of the drops randomly.
> 
> Any help from the experts :-) whould be apreciated.
> 
> 
> Thanks in advence
> Mr Loft
> 
> 
> // --------------------
> // This is the code
> // --------------------
> 
> // ==== Standard POV-Ray Includes ====
> #include "colors.inc"  // Standard Color definitions
> #include "textures.inc"  // Standard Texture definitions
> #include "functions.inc"  // internal functions usable in user defined functions
> #include "rand.inc"   // random number generation macros
> 
> 
> // perspective (default) camera
> camera {
>   location  <0.0, 20, 0.0>
>   look_at   <0.0, 0.0,  -1.0>
>   right     x*image_width/image_height
> }
> 
> 
> // create a regular point light source
> light_source {
>   0*x                  // light's position (translated below)
>   color rgb <1,1,1>    // light's color
>   translate <-20, 40, -20>
> }
> 
> // An area light (creates soft shadows)
> // WARNING: This special light can significantly slow down rendering times!
> light_source {
>   0*x                 // light's position (translated below)
>   color rgb 1.0       // light's color
>   area_light
>   <8, 0, 0> <0, 0, 8> // lights spread out across this distance (x * z)
>   4, 4                // total number of lights in grid (4x*4z = 16 lights)
>   adaptive 0          // 0,1,2,3...
>   jitter              // adds random softening of light
>   circular            // make the shape of the light circular
>   orient              // orient light
>   translate <40, 80, -40>   // <x y z> position of light
> }
> 
> 
> // Create an infinite sphere around scene and allow any pigment on it
> sky_sphere {
>   pigment {
>     gradient y
>     color_map {
>      [0.0 color rgb <0.7,0.7,1.0>]
>      [1.0 color blue 0.5]
>     }
>   }
> }
> 
> // An infinite planar surface
> // plane {<A, B, C>, D } where: A*x + B*y + C*z = D
> plane {
>   y, // <X Y Z> unit surface normal, vector points "away from surface"
>   0 // distance from the origin in the direction of the surface normal
>   pigment {
>    color Red
>   }
>   hollow off // has an inside pigment?
> }
> 
> // ----------------------------------------
> // Scene objects
> // ----------------------------------------
> 
> #declare Blister =
> sphere {
>  <0, 0, 0>, 2
>  texture {
>     pigment{ rgbf <1.0, 1.0, 1.0, .9> }
>     normal {
>         ripples 1
>         frequency 10
>     }
>     finish {
>         reflection {0.3, 1 fresnel}
>         // conserve_energy
>     }
> }
> }
> 
> // ------------------------------------------
> // Copies
> 
> #declare NxRd = seed (23574);
> #declare NyRd = seed (22846);
> #declare NzRd = seed (24784);
> 
> union {
>  #declare FVPos = -100;
>  #declare LVPos = 100;
> 
>   #while ( FVPos < LVPos + 1)
> 
>    #declare FHPos = -100;
>    #declare LHPos = 100;
> 
>     #while ( FHPos < LHPos + 1)
> 
>      object {
>       Blister
>       normal {
>        spotted
>        turbulence 10*rand(RdmC)
> 
>       }
>       translate <5*FHPos+(4*rand(RdmA)), -1.75, 5*FVPos+(4*rand(RdmB))>
>       scale <0.2*NxRd, 0.2*NyRd, 0.2*NzRd>
>      }
> 
>     #declare FHPos = FHPos + 1;
>    #end
>   #declare FVPos = FVPos + 1;
>  #end
> }
> 
> 
It's always beter to translate after you scale, unless you want your scaling to 
also affect the translation.
I'd scale ass follow:
scale<rand(NxRd), rand(NyRd), rand(NzRd)>*0.2
OR
scale<rand(NxRd), rand(NxRd), rand(NxRd)>*0.2 // no need to use separate streams 
here.
Multiplying the translation vector is the same as multiplying each components 
separately.
I'd also use only one stream for the translate.

-- 
Alain
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