Flash MX 2004 Games : Art to ActionScript

Flash MX 2004 Games
Figure B.5 A section of the cosine curve
var n, dt = time/duration;
n = Math.cos(Math.PI/2 * dt + Math.PI) + 1;
_x = offset.x * n + start.x;
_y = offset.y * n + start.y;
For an ease out we will use the curve between 3PI/2 and 2PI; this section of the curve already
gives values between 0 and 1 so we do not need to scale or shift the values.
var n, dt = time/duration;
n = Math.cos((Math.PI * (dt + 3))/2);
_x = offset.x * n + start.x;
_y = offset.y * n + start.y;
The final option is to use the full curve to give both an ease in and out. For this we must use the
full curve between PI and 2PI, the returned values will vary between plus and minus 1 so we must
add 1 then divide by 2 to give returned values between 0 and 1.
var n, dt = time/duration;
n = (Math.cos(Math.PI * dt + Math.PI) + 1)/2;
_x = offset.x * n + start.x;
_y = offset.y * n + start.y;
Exponential tweening
Another curve that can give a very fast ramp is the curve y = 2 x . Any number raised to the
power zero is equal to 1. As you know, the value of dt ranges between 0 and 1, but we
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