Primitives

Shape provides five solid primitives — box, cylinder, sphere, torus, and cone. All are centered at the origin with their axis along +Z; position them with transforms.

// Primitives are centered at the origin; the part transforms here sit each one
// on the ground plane and spread them out for the camera.
var scene = new Scene();
scene.Add(new Part("box", Shape.Box(24, 18, 12), Palette.Steel,
    Matrix4d.CreateTranslation((-40, 0, 6))));
scene.Add(new Part("cylinder", Shape.Cylinder(radius: 9, height: 20), Palette.Brass,
    Matrix4d.CreateTranslation((-13, 0, 10))));
scene.Add(new Part("sphere", Shape.Sphere(radius: 10.5), Palette.Coral,
    Matrix4d.CreateTranslation((13, 0, 10.5))));
scene.Add(new Part("torus", Shape.Torus(majorRadius: 10, minorRadius: 4), Palette.Teal,
    Matrix4d.CreateTranslation((40, 0, 4))));

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Every primitive is available in all three representations — ToBrep() produces exact analytic surfaces (planes, cylinders, spheres, tori), ToImplicit() produces exact signed distance fields, and ToMesh() tessellates. A Box(in Aabb) overload builds a box from explicit bounds instead of a centered size.

Cone

Shape.Cone(bottomRadius, topRadius, height) is the cone frustum (OpenSCAD’s cylinder(r1, r2)): the radius grows linearly from bottomRadius at z = −height/2 to topRadius at z = +height/2. Setting either radius to zero makes that end a pointed apex:

var scene = new Scene();
scene.Add(new Part("frustum", Shape.Cone(bottomRadius: 10, topRadius: 5, height: 14),
    Palette.Copper, Matrix4d.CreateTranslation((-16, 0, 7))));
scene.Add(new Part("apex cone", Shape.Cone(8, 0, 18), Palette.Sage,
    Matrix4d.CreateTranslation((16, 0, 9))));

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Cones are native in all three representations, like the other primitives.

Rigid transforms and uniform scaling keep every primitive exact; shearing a sphere, torus, or cone has no analytic B-Rep surface and is rejected there (Explain names the node) — see the support matrix.