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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 resolution
option which controls tesselation. If resolution
is set to 8, then 8 polygons are used to create 360 degrees of revolution.
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 resolution
for spheres.
EXAMPLE
If the resolution
option is omitted, the following resolution is used.
- CSG.defaultResolution3D = 12
OpenSCAD like functions support the fn
parameter, which is the same as resolution
.
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.
Learn about cylinders at MathIsFun.com
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:
- radius : 1
- 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
- startRadius : [1, 1]
- endRadius : [1, 1]
- center : [0, 0, 0]
- segments : 32
- startAngle : 0
- endAngle : PI * 2
const { cylinderElliptic } = require('@jscad/modeling').primitives const myshape = cylinderElliptic({height: 2, startRadius: [10, 5], endRadius: [8, 3]})
Rounded Cylinder
Cylinders can be created with rounded ends by specifying roundRadius
.
Defaults:
- radius : 1
- height : 2
- roundRadius: 0.5
- center : [0, 0, 0]
- segments : 32
const { roundedCylinder } = require('@jscad/modeling').primitives const myshape = roundedCylinder({radius: 5, height: 10, roundRadius: 0.5}) 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).
Learn about torus at MathIsFun.com
A torus is defined as such:
- Inner Circle
- inner radius
- inner rotation before rotating about the outer circle
- inner segments
- Outer Circle
- outer radius
- outer segments
- Rotation
- start angle of rotation
- outer rotation
Defaults:
- innerRadius : 1
- innerRotation : 0
- innerSegments : 32
- outerRadius : 4
- outerSegments : 32
- startAngle : 0
- outerRotation : PI * 2
const { torus } = require('@jscad/modeling').primitives const myshape = torus({innerRadius: 10, outerRadius: 100})
Polyhedron
A three dimensional shape where connecting faces create a solid. Each face is a three dimensional polygon (a flat shape with straight sides).
Learn about polyhedrons at MathIsFun.com
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'})