ActionScript for Flash MX: The Definitive Guide, Second Edition

MovieClip._droptarget Property

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

Alphabetical Language Reference

|

649

If any of curveTo()’s arguments are missing, the operation fails silently and the position of

the drawing pen remains unchanged. For a description of the drawing pen, see the Discus-

sion under MovieClip.moveTo().

For a primer on Bézier curve mathematics and programming, see:

http://www.ipm.sci-nnov.ru/~demidov/VRML/Splines/Intro/Bezier.htm

Example

Sometimes it is more convenient to specify three points on a curve rather than two anchor

points and a control point. The following code adds a custom curveThrough3Pts() method

to all movie clips; the method accepts three points as arguments and draws a quadratic

curve that passes through them. The second point is assumed to be halfway along the

curve, in time (t = .5):

// Adapted from Robert Penner's drawCurve3Pts() method

MovieClip.prototype.curveThrough3Pts =

function (startX, startY, throughX, throughY, endX, endY) {

var controlX = (2 * throughX) - .5 * (startX + endX);

var controlY = (2 * throughY) - .5 * (startY + endY);

this.moveTo(startX, startY);

this.curveTo(controlX, controlY, endX, endY);

};

// Usage

this.createEmptyMovieClip("drawing_mc", 1);

drawing_mc.lineStyle(1, 0xFF0000);

drawing_mc.curveThrough3Pts(100, 100, 150, 50, 200, 100);

See Also

MovieClip.beginFill()