Struct Turtle3d 

pub struct Turtle3d {
    pub pos: [f32; 3],
    pub heading: [f32; 3],
    pub left: [f32; 3],
    pub up: [f32; 3],
}

The space turtle’s state: a position and an orientation frame of three unit vectors, heading H, left L and up U, with U = H x L.

It starts at the origin heading world +y with left -x and up +z, so a grammar that only yaws draws in the xy plane facing a camera at yaw 0, and turns the same way round as the flat turtle does.

Fields

pos: [f32; 3]

Where the pen is.

heading: [f32; 3]

H: the direction a step moves.

left: [f32; 3]

L: the direction a + turns toward.

up: [f32; 3]

U: H x L.

Implementations

impl Turtle3d

pub fn turn(&mut self, ch: char, angle: f32) -> bool

Apply one turn symbol by angle radians, and say whether ch was one.

• + and - yaw about U, turning H toward and away from L;
• & and ^ pitch about L, turning H away from and toward U;
• \ and / roll about H, turning L toward and away from U;
• | yaws half a turn.

pub fn orthonormalize(&mut self)

Pull the frame back onto an orthonormal one, by Gram-Schmidt in the order H, L, then U = H x L.

Each turn is a rotation in exact arithmetic, but in f32 it leaves the three vectors a few ulps off unit length and off square, and the error compounds: an unbounded walk would shear and grow its steps. Restoring after every turn holds the error to one turn’s worth. H is kept as turned, so a step goes exactly where the turn pointed it.

pub fn step(&mut self)

One step along H.

Trait Implementations

impl Clone for Turtle3d

fn clone(&self) -> Turtle3d

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Turtle3d

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Turtle3d

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for Turtle3d

fn eq(&self, other: &Turtle3d) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Turtle3d

impl StructuralPartialEq for Turtle3d