﻿ disk3D – Algosim documentation
Algosim documentation: disk3D

# disk3D

Creates a new disk in ℝ³.

## Syntax

• `disk3D([a[, f[, d[, α]]]])`

• `a` is a three-dimensional real vector

• `f` is a three-dimensional real vector

• `d` is a three-dimensional real vector

• `α` is a real number

## Description

`disk3D()` creates a circular disk of radius 1 centred at the origin with normal direction `❨0, 0, 1❩`.

`disk3D(a, f, d, α)` translates the disk by `a`, scales it by `diag(f)`, aligns its normal with `d`, and rotates it an amount `α` about its (normal) axis.

Since a disk is flat, the third component of `f` should be unity. Unless the two first components of `f` coincide, the resulting object will be a non-circular elliptic disk.

Hence,

• `a` specifies the position of the disk’s centre.

• `f = (s, t, 1)` specifies the half-axis lengths `s` and `t` of the (elliptic) disk.

• `d` specifies the normal direction of the disk.

• `α` specifies the rotation of the disk about its (normal) axis.

If omitted, `a` defaults to `❨0, 0, 0❩`, `f` to `❨1, 1, 1❩`, `d` to `❨0, 0, 1❩`, and `α` to `0`.

The object is shown in the current scene and a reference to the object is returned.

The `AdjustVisual` function can be used to adjust the appearance of the disk. See Visual settings for a list of applicable settings.

## Examples

`disk3D()`