Add Turtle Class (#17)

* Add Turtle Class

A 3-D turtle with yaw, pitch and roll

* Allow Real for steps then convert to Integer

* Added keywork constructor

* docs changes

src/PiCraft.jl

@@ -1,10 +1,12 @@
 module PiCraft
 
 include("blocks.jl")
+include("turtle.jl")
 
 export World, Block, connectToWorld, mc_send, getBlock, setBlock, setBlocks, getHeight, getPlayerIds
 export setting, saveWorld, restoreWorld, post, getTile, setTile, getPos, setPos, pollBlockHits
 export clearEvents, camera
+export turtle, move, yaw, pitch, roll
 
 type World
     s::TCPSocket

src/turtle.jl

@@ -0,0 +1,66 @@
+"""
+    turtle
+
+A graphics turtle meant to move in all 3-Dimensions. It contains the following fields:
+
+* `pos` : The coordinates of the turtle.
+* `direction` : The Roll Axis - direction in which the turtle is facing.
+* `normal` : The Yaw axis - direction normal to the turtle's body.
+* `penBlock` : The block which will be used to draw.
+* `stepSize` : The size of a turtle's step.
+* `penDown` : Activation state of `penBlock`.
+
+The default constructor initializes the `turtle` at the player's position,roll axis is the positive x-direction,
+with the yaw axis pointing downwards. `penBlock` is gold by default and is activated with the `stepSize` = 0.5
+"""
+mutable struct turtle
+    pos::Tuple{Float64, Float64, Float64}
+    direction::Array{Float64, 1} # Direction turtle is facing, Roll axis
+    normal::Array{Float64, 1} # Direction normal to the turtle's body, Yaw axis
+    penBlock::PiCraft.Block
+    stepSize::Float64
+    penDown::Bool
+
+    turtle(;pos = getPos(), direction = [1.0; 0.0; 0.0], normal = [0.0; -1.0; 0.0], penBlock = Block(41), stepSize = 0.5, penDown = true) = new(pos, direction, normal, penBlock, stepSize, penDown)
+end
+
+"""
+    move(t::turtle, s::Int)
+
+Move the turtle `t` forward `s` steps.
+"""
+function move(t::turtle, s::Real)
+    s = floor(Int, s)
+    for i in 1:s
+        t.penDown && setBlock(t.pos, t.penBlock)
+        t.pos = t.pos .+ Tuple(t.direction*t.stepSize)
+    end
+end
+
+"""
+    pitch(t::turtle, θ::Real)
+
+Pitch the turtle `t` by `θ` degrees.
+"""
+function pitch(t::turtle, θ::Real)
+    yawAxis = cross(t.normal, t.direction)
+    t.normal, t.direction = normalize(t.normal*cosd(θ) + cross(yawAxis, t.normal)*sind(θ)), normalize(t.direction*cosd(θ) + cross(yawAxis, t.direction)*sind(θ))
+end
+
+"""
+    yaw(t::turtle, θ::Real)
+
+Yaw the turtle `t` by `θ` degrees.
+"""
+function yaw(t::turtle, θ::Real)
+    t.direction = normalize(t.direction*cosd(θ) + cross(t.normal, t.direction)*sind(θ))
+end
+
+"""
+    roll(t::turtle, θ::Real)
+
+Roll the turtle `t` by `θ` degrees.
+"""
+function roll(t::turtle, θ::Real)
+    t.normal = normalize(t.normal*cosd(θ) + cross(t.direction, t.normal)*sind(θ))
+end