Turtle Script

Turtle Script creates custom 2D shapes

  • Scripts are parsed within the Logic of 2D shape Geometry.
  • Use a new line for each turtle command.
  • Node parameters and math functions can replace script values
  • The turtle can only read/set parameters on its own node.

Turtle commands fall into a few general categories

  • explicit coordinates: mov, drw, dir, bezier…
  • relative coordinates: rmov, rdrw, arc…
  • self-steering: fwd, back, left, right, turn…
  • logic: let, set, loop, if…

EXPLICIT COORDINATES

the following commands use 2D coordinates and a universal direction,
regardless of the turtle’s current position and orientation

mov x y (a) move to x y (degrees)
teleport turtle to location (face direction)
drw x y draw to location x y
dir a direction angle in degrees
dir 0 is east, dir 90 is north
bezier ax ay ahx ahy bhx bhy bx by segments cubic bezier with 2 handles
startXY handle1 handle2 endXY segments
bezier 0 0 0 1 1 1 1 0 16
molding type ax ay bx by segments tension point-to-point tension curves
type* start end segments tension
tension is normalized 0-1
*types: cove, ovolo, cymarecta, cymareversa, dome
molding 0 1 1 0 16 .5
   

RELATIVE COORDINATES

the following commands use 2D coordinates relative to the turtle’s current position and orientation
newp new point
creates a vertex in-situ
restarts the UV map
rmov dx dy relative move offset-x offset-y
teleport to offset
restarts the UV map
*shape must be OPEN
rdrw dx dy relative draw offset-x offset-y
arcl angle radius segments draw an arc forward and to the left
angle of the full arc, in degrees
radius
of the arc, centered to the left
segments
(int)
arcl 90 1 8
arcr angle radius segments draw an arc forward and to the right
angle of the full arc, in degrees
radius of the arc, centered to the right
segments (int)
arcr 90 1 8
   

ROTATION AND STEERING

the following commands ‘steer’ the turtle according to it’s current rotation and position

movfwd c (d) move forward value (offset)
teleport in the facing direction
*shape must be OPEN
fwd c (d) forward value (offset)
back c (d) back value (offset)
right c (d) right value (offset)
left c (d) left value (offset)
turnl a rotate counter-clockwise degrees
turnr a rotate clockwise degrees
   

LOGIC

the following commands add mathf, temp variables, loops, and conditional logic
closed
closed true
closed false
adds a segment connecting the last point to the first
removes overlapped/enclosed vertices
*required for ‘manifold topology’
*changes options under Shape Output
*also a bool switch under Shape Output
let create a temporary variable (float)
let var value
let myTemp 80
set set value on a parameter or variable
set parameter value
set var value
set myParam 16
loop repeat (count) (step) open a loop and repeat (int) until done
(count) create temp var (int) = the loop value
(step) steps through the count by (int)
loop 360 rotate 90
dir rotate
// rotate = 0, 90, 180, 270

...
endloop
endloop terminate loop
if conditional open a conditional directive when true
if parameter GT value
...

endif
var GT value
var LT value
var GE value
var LE value
var EQ value
var NE value
greater than
less than
greater or equal
lesser or equal
equal
not equal
if bool run conditional when bool is true
if !bool run conditional when bool is false
endif terminate conditional
// comment line
+

*
/
(
)
add
subtract (negative)
multiply
divide
order of operations
mathf functions function returns a value
let hypotenuse sqrt(pow(width,2)+pow(height,2))
parameter the value of a parameter
mov width 0
set width value
DetailLevel read-only parameter from graph: 0-1
*reduces segments on all nodes: 0.5 is 50%
*generates LOD models by reducing vertices
if DetailLevel LT .67
...
endif
   
Values inside () are optional (do not use the brackets)

tips

Each line the turtle draws, creates a new edge and vertex.

When 2D shapes combine into a 3D mesh, the turtle defines how the texture will wrap the model. On the generated mesh U follows the Plan shape and direction, V follows the Section.

‘Steering’ the turtle (ie: fwd, turnl/r) creates clean UV wrapping – easiest method to follow details on a texture map, or create specific vertices on a mesh without stretching the texture.

Unity removes unnecessary vertices to optimize the mesh – which is bad if the mesh needs to deform around a plan. A row of tiny offset points can force vertices in an apparently straight line segment.

Example scripts

The best way to learn AX Turtle Script is to open the Logic panel on any 2D shape to see how it was made.

mov width/2 0 90
drw 0 height/2
drw –width/2 0
drw 0 –height/2

closed true
if shift_origin
molding cove –width height 0 0 segs tension
endif

if !shift_origin
molding cove 0 height width 0 segs tension
endif

closed false
if inputHypotenuse
if solveWidth
set width Sqrt(hypotenuse*hypotenuseheight*height)
endif
set height Sqrt(hypotenuse*hypotenusewidth*width)
endif

set hypotenuse Sqrt(width*width+height*height)
set theta Atan2(height,width)
mov 0 0 90
right width
fwd height

closed true
if bX GE aX
let mdX abs(bXaX)/(segs-1)
endif
if bX LT aX
let mdX -abs(bXaX)/(segs-1)
endif
if bY GE aY
let mdY abs(bYaY)/(segs-1)
endif
if bY LT aY
let mdY -abs(bYaY)/(segs-1)
endif
if cX GE bX
let ndX abs(cXbX)/(segs-1)
endif
if cX LT bX
let ndX -abs(cXbX)/(segs-1)
endif
if cY GE bY
let ndY abs(cYbY)/(segs-1)
endif
if cY LT bY
let ndY -abs(cYbY)/(segs-1)
endif

mov aX aY
loop segs i
mov aX+mdX*i aY+mdY*i
drw bX+ndX*i bY+ndY*i
endloop

Output Shape: open

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