Oseberg tablet jscad

oseberg_tablet.jscad

// title      : Oseberg Weaving Tablets
// author     : Alec Story
// license    : CC by 4.0
// revision   : 1

// Based on a blueprint published in _52 WOOD WEAVING TABLETS
// recovered from The Oseberg Ship Burial in Norway - 834 AD_
// by Terri A. Morrison, 1999.  Dimensions are ultimately from
// her private correspondance with Dr. Arne Emil Christensen,
// chief curator of the Vikingskipshuset in Oslo, Norway.

// All sizes in millimeters, and based on the middle of the
// range of sizes found on the cards, since they vary.

let face_length = 43;
let hole_diameter = 4;
let thickness = 1.5;
let hole_center_inset = 4.5;

// This number is not specified in the documentation.
let corner_radius = 1;
// Set to 8 for faster development renders
let resolution = 100;

function corner_circle(x_dir, y_dir) {
    let offset = face_length / 2 - corner_radius;
    return CAG.circle({center: [offset * x_dir, offset * y_dir],
                       radius: corner_radius,
                       resolution: resolution
    });
}

function hole_circle(x_dir, y_dir) {
    let offset = face_length / 2 - hole_center_inset;
    return CAG.circle({center: [offset * x_dir, offset * y_dir],
                       radius: hole_diameter / 2,
                       resolution: resolution
    });
}

function main() {
   
   let card_polygon = hull(corner_circle(1,   1),
                           corner_circle(1,  -1),
                           corner_circle(-1,  1),
                           corner_circle(-1, -1));
                           
   let polygon_with_holes = card_polygon.subtract([
       hole_circle(1,   1),
       hole_circle(1,  -1),
       hole_circle(-1,  1),
       hole_circle(-1, -1)]);
   
   return linear_extrude({height: thickness}, polygon_with_holes);
}