## 3D Primitives

‘3D’ stands for three (3) dimensional. A 3D primitive is any shape that has three dimensions, which are often called width, depth, and height (or X, Y, Z.) 3D shapes have a known volume if closed.

The mathematical study of 3D shapes and dimensions is called solid geometry.

### Resolution of Shapes

All rounded shapes have a `segments` option which controls tesselation. If `segments` is set to 8, then 8 polygons are used to create a full revolution. If the `segments` option is omitted, the default value is used.

This allows each design to control the amount of detail present, but beware that calculations and rendering time will also increase. For example, the number of polygons increases quadratically with each increase of the `segments` for spheres.

Sometimes, a design requires a certain degree of resolution which is expressed in the length between points, or the angle between points. If this is the case, then use the conversion function to calculate the required segments. See Conversions

### Cuboid

A three dimensional shape created from six retangular faces, each at right angles to another, and opposite faces are equal.

The `size` specifies the size of each face spanning X, Y and Z axis. Cuboids can be created at a requested `center`.

Defaults:

• size : [2, 2, 2]
• center : [0, 0, 0]
```const { cuboid } = require('@jscad/modeling').primitives

const myshape = cuboid({size: [1, 2, 3]})
const myshape = cuboid({size: [1, 2, 3], center: [4, 5, 6]})```

#### Cube The cube is a special case of the cuboid in which all six faces are squares.

Defaults:

• size : 2
• center : [0, 0, 0]
```const { cube } = require('@jscad/modeling').primitives

const myshape = cube({size: 3})
const myshape = cube({size: 3, center: [4, 5, 6]})```

#### Rounded Cuboid Rounded cuboids can be created by specifying a `roundRadius` for the corners.

Defaults:

• size : [2, 2, 2]
• center : [0, 0, 0]
• segments : 32
```const { roundedCuboid } = require('@jscad/modeling').primitives

const myshape = roundedCuboid({size: [1, 2, 3], roundRadius: 0.25})
const myshape = roundedCuboid({size: [1, 2, 3], roundRadius: 0.25, center: [4, 5, 6], segments: 32})```

### Ellipsoid

A three dimensional surface that has three pairwise perpendicular axes of symmetry which intersect at a center. The `radius` determines the size of the ellipsoid about the X, Y, and Z axis. Ellipsoids can be created at a requested `center`. The `segments` specify the number of segments to create per full rotation.

Defaults:

• radius : [1, 1, 1]
• center : [0, 0, 0]
• segments : 32
```const { ellipsoid } = require('@jscad/modeling').primitives

const myshape = ellipsoid({radius: [5, 10, 20]})
const myshape = ellipsoid({radius: [5, 10, 20], center: [5, 5, 5], segments: 64})```

#### Sphere

A three dimensional shape like a ball, where every point on the surface is the same distance from the center. The `radius` determines the size of the sphere. Spheres can be created at a requested `center`. The `segments` specify the number of segments to create per full rotation.

Defaults:

• center : [0, 0, 0]
• segments : 32
```const { sphere } = require('@jscad/modeling').primitives

const myshape = sphere({radius: 3.5, center: [5, 5, 5], segments: 64})```

#### Geodesic Sphere A three dimensional shape formed by a convex polyhedron consisting of triangles. The base form is the icosahedron polyhedron with 20 faces.

The `radius` determines the size of the sphere. The `frequency` specifies the division of each face. A frequency of one (1) reveals the base form, icosahedron.

Defaults:

• frequency : 6
```const { geodesicSphere } = require('@jscad/modeling').primitives

const myshape = geodesicSphere({radius: 15, frequency: 18}) // frequency should be a multiple of 6```

### Cylinder

A three dimensional shape with two flat ends that are circular. The cylinder has the same cross-section from one end to the other, extending about the Z axis.

The `radius` specifies the circular size about the Z axis, while the `height` specifies the size. Cylinders can be created at a requested `center`. The `segments` specify the number of segments to create per full rotation.

Defaults:

• height : 2
• center : [0, 0, 0]
• segments : 32
```const { cylinder } = require('@jscad/modeling').primitives

const myshape = cylinder({radius: 5, height: 10})
const myshape = cylinder({radius: 5, height: 10, center: [5, 5, 5], segments: 64})```

#### Elliptical Cylinder Various cylindrical shapes can be created using the elliptical cylinder, including cylinders with changing radius (cones).

Defaults:

• height : 2
• center : [0, 0, 0]
• segments : 32
• startAngle : 0
• endAngle : PI * 2
```const { cylinderElliptic } = require('@jscad/modeling').primitives

#### Rounded Cylinder Cylinders can be created with rounded ends by specifying `roundRadius`.

Defaults:

• height : 2
• center : [0, 0, 0]
• segments : 32
```const { roundedCylinder } = require('@jscad/modeling').primitives

const myshape = roundedCylinder({radius: 5, height: 10, roundRadius: 0.5, center: [5, 5, 5], segments: 64})```

### Torus

A three dimensional shape made by revolving a small circle (inner) along the circumference a bigger circle (outer).

A torus is defined as such:

• Inner Circle
• inner rotation before rotating about the outer circle
• inner segments
• Outer Circle
• outer segments
• Rotation
• start angle of rotation
• outer rotation

Defaults:

• innerRotation : 0
• innerSegments : 32
• outerSegments : 32
• startAngle : 0
• outerRotation : PI * 2
```const { torus } = require('@jscad/modeling').primitives

### Polyhedron

A three dimensional shape where connecting faces create a solid. Each face is a three dimensional polygon (a flat shape with straight sides). Create a polyhedron from a list of `points` and a list of `faces`. The `points` list all the vertexes of the shape, while the `faces` define the points used within each face.

Note: The order of the points must be consistent, defining 'inward' or 'outward' facing polygons.

```const { polyhedron } = require('@jscad/modeling').primitives

const points = [ [10, 10, 0], [10, -10, 0], [-10, -10, 0], [-10, 10, 0], [0, 0, 10] ]
const faces = [ [0, 1, 4], [1, 2, 4], [2, 3, 4], [3, 0, 4], [1, 0, 3], [2, 1, 3] ]
const myshape = polyhedron({points, faces, orientation: 'inward'})```