study-randompoints.curv

// A study of rendering varyingly shaped points with randomized positions
// with a discrete gradient o density.
//
// Ref: https://www.tylerlhobbs.com/works/item/st-c
//
// It is an opportunity to study randomness (or pseudo-randomness) in curv,
// as well as how to define varying densities of points.

let 

black = [0.051,0.051,0.051];
white = [0.963,0.961,0942];
blue  = [181,235,235]/256;

// That's an infinite volume that we use to give a color to the paper sheet.
paper = make_shape {
    dist (x,y,z,t) = 0;
    is_2d = true;
    is_3d = true;
};

// The grid is useful for debugging
grid_x = make_shape { dist (x,y,z,t) = frac(x) ; is_2d = true ; is_3d = true } 
    >> offset 0.05;
grid_y = make_shape { dist (x,y,z,t) = frac(y) ; is_2d = true ; is_3d = true } 
    >> offset 0.05;


// We're going to introduce some level of variations for the dots:
// - some are going to be squarish, some are going to be roundish
// - some are going to be longer, some are going to be larger
dot (w,k) = make_shape {
    dist (x,y,z,t) =
        let x_ = x; y_ = y; in 
        // Min is union, max is intersection, lerp works to interpolate
        // the shapes.
        lerp(
            // This is the distance function for a square.
            max (abs(x_,y_) - w/2),
            // That's the distance function for a circle.
            (x_*x_ + y_*y_ + z*z - w/2),
            k
        )
    ;
    is_2d = true;
    is_3d = true;
};

// Here we're creating a grid, we know that the dots are 1 unit wide
// (by default). We apply the `mod` function to *repeat* the shape
// along the X and Y axes. The step of the `mod` must be at least the
// width and the shifting should be the width.
dots shape = make_shape {

    dist (x,y,z,t) = shape.dist(
        mod(x,2) - 1,
        mod(y,2) - 1,
        z,t
    );
    is_2d = true;
    is_3d = true;
};



// Now for every dot we'll need to hide some of them. As each dot fits within
// a 2 x 2 cells.

nsin x = (sin (x) + 1) / 2;

roundby (a,b) = round(a/b) * b;

// A random function from the Book of Shaders https://thebookofshaders.com/10/
rand x = frac(sin(x)*1000000.0);
mask shape = make_shape {
    dist (x,y,z,t) = 
        max(
            round(nsin (roundby(x,4)*10000)) * 1,//round(mod(x,4)/4) * round(mod(y,4)/4),
            shape.dist(x,y,z,t)
        );
    is_2d = true;
    is_3d = true;
}

in union [
    paper >> colour (white),
    grid_x  >> colour (blue),
    grid_y  >> colour (blue),
    dot (1,0.5) >> dots >> mask >> colour (black)
]

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