Module Mlpost.MetaPath

MetaPaths: gradually build a path with constraints, get a real path at thxe end.

MetaPaths are the objects used to describe lines, curves, and more generally almost everything that is drawn with Mlpost. A path (Path.t) is defined by points and control points. A metapath is defined by points (knots) and constraints on the links between the points. A metapath is an easy way to define a path gradually with only a few points, and apply heuristics afterwards to transform it into a real path (using of_metapath).

type direction = Path.direction

A direction is used to put constraints on metapaths:

  • vec p defines a direction by a point (interpreted as a vector)
  • curl f changes the curling factor of the extremity of a metapath; higher curling factor means flatter curves
  • noDir means no particular direction
val vec : Point.t -> direction
val curl : float -> direction
val noDir : direction
type knot = Path.knot

A knot is the basic element of a metapath, and is simply a point with an incoming and outgoing direction constraint

val knotp : ?l:direction -> ?r:direction -> Point.t -> knot

Build a knot from a point; the optional arguments are the incoming directions.Warning they are going in the same direction.

val knotlist : (direction * Point.t * direction) list -> knot list
type joint = Path.joint

A joint is the connection between two knots in a metapath. It is either

  • jLine for a straight line
  • jCurve for a spline curve
  • jCurveNoInflex to avoid inflexion points
  • jTension f1 f2 to specify "tension" on the joint; jCurve uses a default tension of 1. Higher tension means less "wild" curves
  • jControls p1 p2 to explicitely specify control points
val jLine : joint
val jCurve : joint
val jCurveNoInflex : joint
val jTension : float -> float -> joint
val jControls : Point.t -> Point.t -> joint
type t

The abstract type of metapaths

type path = Path.t

In all the functions below :

Labelled metapath constructors

val knot : ?l:direction -> ?r:direction -> ?scale:(float -> Num.t) -> (float * float) -> knot

Build a knot from a pair of floats

  • parameter l

    an incoming direction

  • parameter r

    an outgoing direction

  • parameter scale

    a scaling factor applied to the floats

val knotn : ?l:direction -> ?r:direction -> (Num.t * Num.t) -> knot

Build a knot from a Num.t pair; the optional arguments are as in knot

val path : ?style:joint -> ?scale:(float -> Num.t) -> (float * float) list -> t

Build a metapath from a list of pairs of floats

  • parameter style

    the joint style used for all joints in the metapath

  • parameter cycle

    if given, the metapath is closed using the given style

  • parameter scale

    permits to scale the whole metapath

val pathn : ?style:joint -> (Num.t * Num.t) list -> t

Same as metapath, but uses a Num.t list

val pathk : ?style:joint -> knot list -> t

Same as metapath, but uses a knot list

val pathp : ?style:joint -> Point.t list -> t

Same as metapath but uses a point list

val jointpathk : knot list -> joint list -> t

Build a metapath from n knots and n-1 joints

val jointpathp : Point.t list -> joint list -> t

Build a metapath from n points and n-1 joints, with default directions

val jointpathn : (Num.t * Num.t) list -> joint list -> t
val jointpath : ?scale:(float -> Num.t) -> (float * float) list -> joint list -> t

Build a metapath from n float_pairs and n-1 joints, with default directions

val cycle : ?dir:direction -> ?style:joint -> t -> path

Close a metapath using direction dir and style style

Primitive metapath constructors

val concat : ?style:joint -> t -> knot -> t

Add a knot at the end of a metapath

val start : knot -> t

Create a simple metapath with one knot

val append : ?style:joint -> t -> t -> t

Append a metapath to another using joint style

Predefined values

val defaultjoint : joint

The default joint style (JCurve)

Conversions

val to_path : t -> path

Compute the control point of the path for a good looking result according to the constraint on the direction, tension, curve

val of_path : path -> t

Obtain a metapath from a path with exactly the same control point. p = of_metapath (of_path p) is true but not the opposite.