com.jsevy.adxf

Class BSpline

java.lang.Object

com.jsevy.adxf.BSpline

public class BSpline
extends Object

Constructor Summary

Constructors

Constructor and Description
BSpline(int degree, float[] controlPoints, int[] multiplicities, boolean throughEndpoints) Create a spline of the specified degree using the supplied x,y coordinate pairs as the control points.
BSpline(int degree, Vector<SplineControlPoint> controlPoints) Create e new B-spline of the specified degree using the supplied control points

Method Summary

Modifier and Type	Method and Description
static void	drawSpline(Canvas canvas, int degree, float[] controlPoints, int[] multiplicities, boolean throughEndpoints, float tolerance, Paint paint) An extension method that supports the drawing of a B-spline.
Vector<RealPoint>	getCurvePoints(float tolerance) Get a set of points on the spline curve, where the maximum distance between two adjacent points is given by tolerance.
String	toString()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

BSpline

public BSpline(int degree,
               Vector<SplineControlPoint> controlPoints)

Create e new B-spline of the specified degree using the supplied control points

Parameters:

degree - Degree of the spline polynomial pieces

controlPoints - The set of control points used to define the spline

BSpline

public BSpline(int degree,
               float[] controlPoints,
               int[] multiplicities,
               boolean throughEndpoints)

Create a spline of the specified degree using the supplied x,y coordinate pairs as the control points.

Parameters:

degree - The degree of the underlying piecewise-polynomial segments

controlPoints - The control points used to define the shape of the spline, {x1, y1, x2, y2, ..., xn, yn}

multiplicities - Array giving the multiplicity of each of the control points. The size of the multiplicities must be half the size of the controlPoints array.

throughEndpoints - Set true to force the spline curve to pass through the end control points. This is accomplished by forcing the multiplicity of the first and last control points to degree + 1. Note that this will give a different spline curve than that typically referred to as a "clamped" spline, in which the spline knots are repeated at the beginning and end to force the spline to pass through these points. The repeated control-point approach has the advantage of having the "open" spline (where throughEndpoints is false) being a subset of the "closed" curve; this is not true for "unclamped" and "clamped" splines.

Method Detail

drawSpline

public static void drawSpline(Canvas canvas,
                              int degree,
                              float[] controlPoints,
                              int[] multiplicities,
                              boolean throughEndpoints,
                              float tolerance,
                              Paint paint)

An extension method that supports the drawing of a B-spline. If the supplied Canvas is an instance of DXFCanvas, this generates a native DXF spline type. For other Canvas types, this draws the spline as a set of line segments since there are no native spline-drawing routines in the standard Android. The tolerance parameter indicates the maximum length of each line segment to control the smoothness of the representation. For the common case of a spline that passes through the first and last control points, set the multiplicity of these equal to the spline degree plus 1, or set the throughEndpoints parameter to true, which does the same internally.

Parameters:

degree - The degree of the spline; must be > 0

controlPoints - The control points that define the shape of the spline, {x1, y1, x2, y2, ..., xn, yn}.

multiplicities - The multiplicities for the control points; the number of multiplicity values must equal the number of control points (i.e., the array size must be half that of the controlPoints array)

throughEndpoints - If true, the spline will be forced to pass through the endpoints by setting the end control point multiplicities to degree + 1

tolerance - For non-DXF canvas types, the spline is drawn as a set of connected line segments; the tolerance specifies that maximum lenth of each line segment to control the smoothness of the representation. Ignored for DXFCanvas, which has a true spline representation.

paint - The Paint object used to draw the spline

getCurvePoints

public Vector<RealPoint> getCurvePoints(float tolerance)

Get a set of points on the spline curve, where the maximum distance between two adjacent points is given by tolerance.

Parameters:

tolerance - The maximum distance between any two adjacent points in the return vector

Returns:

A vector containing a set of points which lie on the spline curve

toString

public String toString()

Overrides:

toString in class Object