Demo: Interpolating Points on a Sine Curve
Source: interpolate_sine.zip

A recent post on the gotoAndPlay.net flashlist asked about charting the sine wave in flash using the drawing API. The problem with the drawing API is that the quadratic bezier curveTo functions don’t make for the smoothest curves without a little trickery.

Patrick Mineault has a great piece on his blog about piecewise cubic beziers. Using his code, we can interpolate between the points on a sine curve quite smoothly. I thought his demo was quite nice, so I download his source, hacked it a bit, and came up with this demo.

Yes, it makes a nice smooth curve, if that’s what you’re after, but the fun starts when you start playing with the controls. A good place to start is by setting the wavelength to 2 while increasing the overshoot. Once the wavelength gets below 4 pixels, the cubic bezier interpolation no longer has enough points to interpolate the high frequency wave accurately. Increasing the overshoot factor creates some unexpectedly fun curls. Altering the number of points plotted gives us even more variation.

FTween is a simple tweening utility designed to fill a need not met by the Penner family of time-based tweening solutions. The problem case is one where a target is constantly moving and/or changing at unexpected times. The Penner equations rely on the assumption that a tween will last for a known length of time, but it is often the case that I simply want a smooth transition from one state to another. Tweening content for smooth scrolling and animating a tree menu are two common examples where time-based tweening can have stuttering or less than desirable result. When animating a sprite in such as way that it follows a moving target, Penner tweens don’t work at all.

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MTASC, the open-source Actionscript compiler, has become an essential part of my daily routine. I used it for a long time with custom built BAT files that would inject compiled code into my library SWF’s, but now I can do all of this with FlashDevelop. There are other editors out there, but FlashDevelop is my current IDE of choice, and it just so happens that it has a cute little feature I’ve not seen elsewhere. That feature is called “Quick MTASC Build”, and I use it all the time to build quick test SWF’s without ever having to open up the Flash authoring environment. I refer to these FLA-less SWF’s as MTASC Applets.

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Much has been written about smoothing dynamically loaded bitmaps in Flash 8. But, just in case you missed it, here’s the short version: Flash 8 allows you to smooth dynamically loaded images such as JPG’s at runtime by taking a snapshot of the image using BitmapData and redrawing it on to a MovieClip with smoothing applied..

It’s one of those things you may never have realized you were missing until now.

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