pentatonic pineapple draft

optic mold.stl

positive for printing.stl

// openjscad

const TWO_PI = 2.0 * 3.14159265;

function getParameterDefinitions () {
  return ([
    {name: 'height', type: 'float', initial: 50,caption: 'Height'},
    {name: 'topWidth', type: 'float', initial: 50, caption: 'Top width'},
    {name: 'bottomWidth', type: 'float', initial: 30,  caption: 'Bottom width'},
    {name: 'bumpSize', type: 'float', initial: 5, caption: 'bump size'}
  ]);
}

var tiltAngle, tiltLength;

function main(params) {
    tiltAngle = -90 + 360 / TWO_PI * Math.atan2(params.height, params.bottomWidth/2-params.topWidth/2);
    var diff = params.topWidth/2 - params.bottomWidth / 2;
    tiltLength = Math.sqrt(params.height*params.height + diff*diff);
    
    params.bumpSize = tiltLength / 6;
    
    /*
    return union(
        cone(),
        bumps()
    );
    */
    //return positive();
    return mold();
    //return thinPositive();
}   

function mold() {
    return difference(
        scale([1.1,1.1,1.0], cone()),
        positive()
    )
}

function thinPositive() {
    return difference(
        positive(),
        scale([0.82,0.82,1.0], cone())
    )
}

function positive() {
    return difference(
        cone(),
        bumps()
    );
}

function cone() {
    return cylinder({r1:params.bottomWidth/2, r2:params.topWidth/2, h:params.height});
}

function bumps() {
    var bs = [];
    for (var j=0; j<6; j++) {
        var n = [15,18,20,24,27,30][j]
        for (var i=0; i<n; i++) {
            bs.push(bump(8*j,360 * i / n));
        }
    }
    return union(
        bs
    );
}


function bump(h, a) {
    return translate([0,0,h], 
        rotate([0,0,a], 
            translate([extrapolatedRadius(h)+params.bumpSize/2,0,params.bumpSize/2.0], 
                rotate([0, tiltAngle, 0],
                    bevelBump()
                    //simpleBump()
                )
            )
        )
    );
}

// no good
function simpleBump() {
    return rotate([45,45,45], cube({size: params.bumpSize, center:true}))
}

function bevelBump() {
    return intersection(
      rotate([0,0,45], cube({size: params.bumpSize, center:true})),
      rotate([45,0,45], cube({size: params.bumpSize*1.1, center:true})),
      rotate([0,45,45], cube({size: params.bumpSize*1.1, center:true}))
    )
}

function extrapolatedRadius(h) {
    let t = h / params.height;
    return params.bottomWidth/2 + (params.topWidth/2 - params.bottomWidth/2) * t;
}

diatonic version: https://gist.github.com/moonmilk/d519ba822a1768fc56029e17e9a80d90