//
// leskinen.petri@luukku.com
// - please send me a note if you use the code for anything cool !
//

kernel Crystallize
<   nameSpace : "by Petri Leskinen";
    vendor : "";
    version : 1;
    description : "Crystallize -filter";
>
{

//@ parameter(s)

    input image4 src;
    output pixel4 dst;

        parameter float size
    <
        minValue: float(1.0);
        maxValue: float(300.0);
        defaultValue: float(1.0);
        description: "size";
    >;

//@ matrices
    
    // rot1: rotation matrix, 18 degrees
    // rot1r: reverse rotation, -18 degrees
    // base1: rotation base point (somewhere far enough from origin)
    const float2x2 rot1 = float2x2(0.951,0.309,-0.309,0.951);
    const float2x2 rot1r = float2x2(0.951,-0.309,0.309,0.951);
    const float2 base1= float2(2400,-100);

    // rot2: rotation matrix, 30 degrees
    // rot2r: reverse rotation, -30 degrees
    // base2: base point 
    const float2x2 rot2 = float2x2(0.866,0.5,-0.5,0.866); // 30 degress
    const float2x2 rot2r = float2x2(0.866,-0.5,0.5,0.866);
    const float2 base2= float2(-100,2400);

//@ evaluate(s)
    
    void
    evaluatePixel()
    {
        // Crystallize, pseudo Voronoi-diagram using three nearby points,
        // calculated from 'randomly' placed and rotated rectangular grids 
        
        // 1st grid and point
        float div=size;
        float2 newP= base1 + rot1r*div*( floor( rot1*(outCoord()-base1)/div ) +0.5);
        
        // 2nd grid
        div= 21.0/20.0*size; // factor 21, I picked some number that has no common denominators with the default size 20
        float2 p= base2 + rot2r*div*( floor( rot2*(outCoord()-base2)/div  ) +0.5);
        // comparing distance to the 1st sample point
        newP =  length(p-outCoord()) < length(newP-outCoord()) ? p : newP;

        // 3rd grid
        div= 19.0/20.0*size;
        p= div*( floor( outCoord()/div  ) +0.5);
        // comparing distance
        newP =  length(p-outCoord()) < length(newP-outCoord()) ? p : newP;
        
        // the new color is picked from the nearist point
        dst = sampleNearest(src,newP);
    }
}