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Bottle Example

OpenCascade's bottle example is one of the classic examples of that library. The code below is a translation of the original C++ code into JavaScript.

const { width, height, thickness } = params;

// Profile : Define Support Points
const aPnt1 = new oc.gp_Pnt_3(-width / 2., 0, 0);
const aPnt2 = new oc.gp_Pnt_3(-width / 2., -thickness / 4., 0);
const aPnt3 = new oc.gp_Pnt_3(0, -thickness / 2., 0);
const aPnt4 = new oc.gp_Pnt_3(width / 2., -thickness / 4., 0);
const aPnt5 = new oc.gp_Pnt_3(width / 2., 0, 0);

// Profile : Define the Geometry
const anArcOfCircle = new oc.GC_MakeArcOfCircle_4(aPnt2, aPnt3, aPnt4);
const aSegment1 = new oc.GC_MakeSegment_1(aPnt1, aPnt2);
const aSegment2 = new oc.GC_MakeSegment_1(aPnt4, aPnt5);

// Profile : Define the Topology
const anEdge1 = new oc.BRepBuilderAPI_MakeEdge_24(new oc.Handle_Geom_Curve_2(aSegment1.Value().get()));
const anEdge2 = new oc.BRepBuilderAPI_MakeEdge_24(new oc.Handle_Geom_Curve_2(anArcOfCircle.Value().get()));
const anEdge3 = new oc.BRepBuilderAPI_MakeEdge_24(new oc.Handle_Geom_Curve_2(aSegment2.Value().get()));
const aWire = new oc.BRepBuilderAPI_MakeWire_4(anEdge1.Edge(), anEdge2.Edge(), anEdge3.Edge());

// Complete Profile
const xAxis = oc.gp.OX();
const aTrsf = new oc.gp_Trsf_1();

aTrsf.SetMirror_2(xAxis);
const aBRepTrsf = new oc.BRepBuilderAPI_Transform_2(aWire.Wire(), aTrsf, false);
const aMirroredShape = aBRepTrsf.Shape();

const mkWire = new oc.BRepBuilderAPI_MakeWire_1();
mkWire.Add_2(aWire.Wire());
mkWire.Add_2(oc.TopoDS.Wire_1(aMirroredShape));
const myWireProfile = mkWire.Wire();

// Body : Prism the Profile
const myFaceProfile = new oc.BRepBuilderAPI_MakeFace_15(myWireProfile, false);
const aPrismVec = new oc.gp_Vec_4(0, 0, height);
let myBody = new oc.BRepPrimAPI_MakePrism_1(myFaceProfile.Face(), aPrismVec, false, true);

// Body : Apply Fillets
const mkFillet = new oc.BRepFilletAPI_MakeFillet(myBody.Shape(), oc.ChFi3d_FilletShape.ChFi3d_Rational);
const anEdgeExplorer = new oc.TopExp_Explorer_2(myBody.Shape(), oc.TopAbs_ShapeEnum.TopAbs_EDGE, oc.TopAbs_ShapeEnum.TopAbs_SHAPE);
while (anEdgeExplorer.More()) {
  const anEdge = oc.TopoDS.Edge_1(anEdgeExplorer.Current());
  // Add edge to fillet algorithm
  mkFillet.Add_2(thickness / 12., anEdge);
  anEdgeExplorer.Next();
}
myBody = mkFillet.Shape();

// Body : Add the Neck
const neckLocation = new oc.gp_Pnt_3(0, 0, height);
const neckAxis = oc.gp.DZ();
const neckAx2 = new oc.gp_Ax2_3(neckLocation, neckAxis);

const myNeckRadius = 5;
const myNeckHeight = 5;

const MKCylinder = new oc.BRepPrimAPI_MakeCylinder_3(neckAx2, myNeckRadius, myNeckHeight);
const myNeck = MKCylinder.Shape();

myBody = new oc.BRepAlgoAPI_Fuse_3(myBody, myNeck, new oc.Message_ProgressRange_1());

// Body : Create a Hollowed Solid
let faceToRemove;
let zMax = -1;
const aFaceExplorer = new oc.TopExp_Explorer_2(myBody.Shape(), oc.TopAbs_ShapeEnum.TopAbs_FACE, oc.TopAbs_ShapeEnum.TopAbs_SHAPE);
for (; aFaceExplorer.More(); aFaceExplorer.Next()) {
  const aFace = oc.TopoDS.Face_1(aFaceExplorer.Current());
  // Check if <aFace> is the top face of the bottle's neck 
  const aSurface = oc.BRep_Tool.Surface_2(aFace);
  if (aSurface.get().$$.ptrType.name === "Geom_Plane*") {
    const aPlane = new oc.Handle_Geom_Plane_2(aSurface.get()).get();
    const aPnt = aPlane.Location();
    const aZ = aPnt.Z();
    if (aZ > zMax) {
      zMax = aZ;
      faceToRemove = new oc.TopExp_Explorer_2(aFace, oc.TopAbs_ShapeEnum.TopAbs_FACE, oc.TopAbs_ShapeEnum.TopAbs_SHAPE).Current();
    }
  }
}

const facesToRemove = new oc.TopTools_ListOfShape_1();
facesToRemove.Append_1(faceToRemove);
const s = myBody.Shape();
myBody = new oc.BRepOffsetAPI_MakeThickSolid();
myBody.MakeThickSolidByJoin(s, facesToRemove, -thickness / 50, 1.e-3, oc.BRepOffset_Mode.BRepOffset_Skin, false, false, oc.GeomAbs_JoinType.GeomAbs_Arc, false, new oc.Message_ProgressRange_1());
// Threading : Create Surfaces
const aCyl1 = new oc.Geom_CylindricalSurface_1(new oc.gp_Ax3_2(neckAx2), myNeckRadius * 0.99);
const aCyl2 = new oc.Geom_CylindricalSurface_1(new oc.gp_Ax3_2(neckAx2), myNeckRadius * 1.05);

// Threading : Define 2D Curves
const aPnt = new oc.gp_Pnt2d_3(2. * Math.PI, myNeckHeight / 2.);
const aDir = new oc.gp_Dir2d_4(2. * Math.PI, myNeckHeight / 4.);
const anAx2d = new oc.gp_Ax2d_2(aPnt, aDir);

const aMajor = 2. * Math.PI;
const aMinor = myNeckHeight / 10;

const anEllipse1 = new oc.Geom2d_Ellipse_2(anAx2d, aMajor, aMinor, true);
const anEllipse2 = new oc.Geom2d_Ellipse_2(anAx2d, aMajor, aMinor / 4, true);
const anArc1 = new oc.Geom2d_TrimmedCurve(new oc.Handle_Geom2d_Curve_2(anEllipse1), 0, Math.PI, true, true);
const anArc2 = new oc.Geom2d_TrimmedCurve(new oc.Handle_Geom2d_Curve_2(anEllipse2), 0, Math.PI, true, true);
const tmp1 = anEllipse1.Value(0);
const anEllipsePnt1 = new oc.gp_Pnt2d_3(tmp1.X(), tmp1.Y());
const tmp2 = anEllipse1.Value(Math.PI);
const anEllipsePnt2 = new oc.gp_Pnt2d_3(tmp2.X(), tmp2.Y());

const aSegment = new oc.GCE2d_MakeSegment_1(anEllipsePnt1, anEllipsePnt2);
// Threading : Build Edges and Wires
const anEdge1OnSurf1 = new oc.BRepBuilderAPI_MakeEdge_30(new oc.Handle_Geom2d_Curve_2(anArc1), new oc.Handle_Geom_Surface_2(aCyl1));
const anEdge2OnSurf1 = new oc.BRepBuilderAPI_MakeEdge_30(new oc.Handle_Geom2d_Curve_2(aSegment.Value().get()), new oc.Handle_Geom_Surface_2(aCyl1));
const anEdge1OnSurf2 = new oc.BRepBuilderAPI_MakeEdge_30(new oc.Handle_Geom2d_Curve_2(anArc2), new oc.Handle_Geom_Surface_2(aCyl2));
const anEdge2OnSurf2 = new oc.BRepBuilderAPI_MakeEdge_30(new oc.Handle_Geom2d_Curve_2(aSegment.Value().get()), new oc.Handle_Geom_Surface_2(aCyl2));
const threadingWire1 = new oc.BRepBuilderAPI_MakeWire_3(anEdge1OnSurf1.Edge(), anEdge2OnSurf1.Edge());
const threadingWire2 = new oc.BRepBuilderAPI_MakeWire_3(anEdge1OnSurf2.Edge(), anEdge2OnSurf2.Edge());
oc.BRepLib.BuildCurves3d_2(threadingWire1.Wire());
oc.BRepLib.BuildCurves3d_2(threadingWire2.Wire());
oc.BRepLib.BuildCurves3d_2(threadingWire1.Wire());
oc.BRepLib.BuildCurves3d_2(threadingWire2.Wire());

// Create Threading 
const aTool = new oc.BRepOffsetAPI_ThruSections(true, false, 1.0e-06);
aTool.AddWire(threadingWire1.Wire());
aTool.AddWire(threadingWire2.Wire());
aTool.CheckCompatibility(false);

const myThreading = aTool.Shape();

// Building the Resulting Compound 
const aRes = new oc.TopoDS_Compound();
const aBuilder = new oc.BRep_Builder();
aBuilder.MakeCompound(aRes);
aBuilder.Add(aRes, myBody.Shape());
aBuilder.Add(aRes, myThreading);

// Rotate our finished bottle upright
const tf = new oc.gp_Trsf_1();
tf.SetRotation_1(new oc.gp_Ax1_2(new oc.gp_Pnt_1(), new oc.gp_Dir_4(1, 0, 0)), -Math.PI/2);
const loc = new oc.TopLoc_Location_2(tf);

visualizeShapes(aRes.Moved(loc, false));
width: 50
height: 70
thickness: 30
What exactly is happening here?

Head over to the OpenCascade tutorial for this example for a detailed explanation of all the steps involved.