hexagon2.osl

#define A 0.86602540378443864676372317075294 // sqrt(3)/2
#define A2 (2*A)
#define A4 (4*A)
#define SY (1/A)

#define SWAP(t,a,b) t=a; a=b; b=t

shader hexagons(
    color  Diffuse_Color1 = color(0.2, 0.8, 0.2),
    color  Diffuse_Color2 = color(0.8, 0.2, 0.2),
    color  Diffuse_Color3 = color(0.2, 0.2, 0.8),
    float  Width          = 0.05,
    vector Coordinates    = 0,
    
    output color Color  = 0,
    output int   Index  = 1,
    output float Center = 0,
    output float Edge   = 0,
    output int   InEdge = 0
){
    // calculate the colors
    
    color colors[3] = {Diffuse_Color1,
                       Diffuse_Color2,
                       Diffuse_Color3};   
 
    // we warp the grid so that two adjacent equilateral triangles
    // are mapped to two triangles that fit in a square
    float syc = Coordinates[1] * SY;
    float sxc = Coordinates[0] + 0.5 * syc;
 
    int ind[18] = {1,1,3,3,3,1, 2,2,2,3,3,3, 1,2,2,2,1,1};
 
    int iy = int(mod(syc,3.0));
    int ix = int(mod(sxc,3.0));
    ix = iy * 6 + ix * 2 + ( mod(sxc,1.0) > mod(syc,1.0) );    
    Index = ind[ix];
    Color = colors[Index-1];    
 
    // calculate the distance to the center of the hexagon
       
    float sx = mod(Coordinates[0],3);
    float sy = mod(Coordinates[1]+0.75,A4); 

    // map everthing to a single quadrant
    if ( sx > 1.5 ) sx = 3 - sx;
    if ( sy > A2 ) sy = A4 - sy;
    
    // distance to nearest edge
    
    float x = mod(Coordinates[0]/3,1.0);
    float y = mod(Coordinates[1]/3,A2);
   
    #define N 18
    vector hc[N] = {
        vector(  0, -A2/3     ,0),
        vector(  0,     0     ,0),
        vector(  0,  A2/3     ,0),
        vector(  0,2*A2/3     ,0),
        vector(  0,  A2       ,0),
        vector(  0,4*A2/3     ,0),

        vector(0.5, -A2/3+A2/6,0),
        vector(0.5,     0+A2/6,0),
        vector(0.5,  A2/3+A2/6,0),
        vector(0.5,2*A2/3+A2/6,0),
        vector(0.5,  A2  +A2/6,0),
        vector(0.5,4*A2/3+A2/6,0),

        vector(1.0, -A2/3     ,0),
        vector(1.0,     0     ,0),
        vector(1.0,  A2/3     ,0),
        vector(1.0,2*A2/3     ,0),
        vector(1.0,  A2       ,0),
        vector(1.0,4*A2/3     ,0)
    };
    
    float d[N], t;
    
    for(int i=0; i < N; i++){
        float dx = x - hc[i][0];
        float dy = y - hc[i][1];
        d[i] = hypot(dx, dy); 
    }
    
    for(int j= N-1; j >= 0; j--){
        for(int i= 0; i < j; i++){
            if(d[i] > d[i+1]){ 
                SWAP(t, d[i], d[i+1]);
            }
        }
    }
    
    Center  = d[0];
    Edge    = d[1] - d[0];
    InEdge  = Edge < Width;
}