OpenJsCad demo: Parametric S hook

Source code

Below is the OpenJsCad script for this demo. To build your own models, create a .jscad script and use the OpenJsCad parser. For more information see the OpenJsCad documentation.

// Here we define the user editable parameters: 
function getParameterDefinitions() {
  return [
    { name: 'topdiameter', caption: 'Inner diameter of top hook:', type: 'float', default: 10 },
    { name: 'clampfactor', caption: 'Snugness of top hook (0 - 100):', type: 'float', default: 20 },
    { name: 'cliplength', caption: 'Top hook clip length:', type: 'float', default: 5 },
    { name: 'bottomdiameter', caption: 'Inner diameter of bottom hook:', type: 'float', default: 15 },
    { name: 'height', caption: 'Outer height of the hook:', type: 'float', default: 50 },
    { name: 'thickness', caption: 'Thickness:', type: 'float', default: 5 },
    { name: 'width', caption: 'Width:', type: 'float', default: 10 },
    {
      name: 'rounded', 
      type: 'choice',
      caption: 'Rounded edges',
      values: [0, 1],
      captions: ["No", "Yes (rendering will take a long time!)"], 
      default: 0,
    },    
    { name: 'roundness', caption: 'Diameter of rounded edges (if enabled):', type: 'float', default: 1 },
  ];
}

function main(params) {
  var pathresolution = 16;
  var expandresolution = 16;
  
  // construct the 2D path:
  var topradius = params.topdiameter/2;
  var bottomradius = params.bottomdiameter/2;
  var halfthickness = params.thickness/2;
  topradius += halfthickness;
  bottomradius += halfthickness;
  
  var roundness = params.roundness;
  if(params.rounded == 0)
  {
    roundness = 0;
  }
  roundness = Math.min(roundness, halfthickness-0.1, params.width/2-0.1);
  if(roundness < 0) roundness = 0;
  
  var clampfactor = params.clampfactor / 100;
  if(clampfactor < 0) clampfactor = 0;
  if(clampfactor >= 1) clampfactor = 1;
  clampfactor *= (topradius-halfthickness)/topradius;  
  
  var topstartangle = - 180 * Math.acos(1 - 2*clampfactor) / Math.PI;
  var tophookcenter = new CSG.Vector2D(topradius, 0);
  var tophookstart = tophookcenter.plus(CSG.Vector2D.fromAngleDegrees(topstartangle).times(topradius));
  var circledistance = params.height - topradius - bottomradius - 2 * params.thickness;
  if(circledistance < 0) circledistance = 0;
  var bottomhookcenter = new CSG.Vector2D(-bottomradius, -circledistance);
  var gravityangle = 90 - tophookcenter.minus(bottomhookcenter).angleDegrees();
  
  var path = new CSG.Path2D();

// top hook curve:
  if(params.cliplength > 0)
  {
    var clipstart = new CSG.Vector2D([0, -1]).times(params.cliplength).plus(tophookstart);
    path = path.appendPoint(clipstart);
  }
  var topcurvepath = CSG.Path2D.arc({
    center: tophookcenter,
    radius: topradius,
    startangle: topstartangle,
    endangle: 180,
    resolution: pathresolution,
    maketangent: true,
  });
  path = path.concat(topcurvepath);

// straight middle part:
  if(circledistance > 0)
  {
    path = path.appendPoint([0, -circledistance]);
  }
  
  // bottom hook curve:
  var bottomcurvepath = CSG.Path2D.arc({
    center: bottomhookcenter,
    radius: bottomradius,
    startangle: 0,
    endangle: -180-gravityangle,
    resolution: pathresolution,
    maketangent: true,
  });
  path = path.concat(bottomcurvepath);
  
  // center around origin, and rotate as it would hang under gravity:
  var centerpoint = tophookcenter.plus(bottomhookcenter).times(0.5);  
  var matrix = CSG.Matrix4x4.translation(centerpoint.negated().toVector3D(0));
  matrix = matrix.multiply(CSG.Matrix4x4.rotationZ(gravityangle));
  path = path.transform(matrix);

// extrude the path to create a 3D solid
  var result = path.rectangularExtrude(2*(halfthickness-roundness), params.width-2*roundness, pathresolution, true);
  result = result.translate([0, 0, -params.width/2+roundness]);
  
  // expand to create rounded corners:
  if(roundness > 0)
  {
    result = result.expand(roundness, expandresolution);
  }
   
  return result;
}