If you are currently using motion tweens to create circular motion for your movie clips I urge you to use actionscript instead.
Not only is it easier, it is also more adaptable.
For example if you want to change the rotational speed of the clip simply change the number that controls it.
Another advantage is file size, especially when the motion is slow. Added frames equals greater .swf file size.
As the examples below show there are also many variations you can use.
If you are new to actionscript you need to know that code can be attached to a frame or to a movie clip. They are distinctly different. The "onClipEvent" handler will only work when attached to a movie clip.
When code is attached to a frame you will see a lower case "a" in the frame.
Click the movie clip so that the code is attached to the clip and not to the frame. You should not see a lower case "a" in the frame when it is attached to the movie clip.
The animation to the right shows an important property of movie clip rotation in Flash. After 180 degrees, Flash interprets the rotation as a negative number.
The code attached to the outer (slowest) ring is:
onClipEvent (enterFrame)
{
this._rotation+=1;
}
The number "1" specifies how many degrees the clip will rotate each frame. This number varies for each ring which is why they rotate at different speeds.
At first glance it would seem that "_rotation" would increment endlessly and necessitate additional code to reset it back to zero after "_rotation" reaches 360 degrees.
You will need to keep this in mind when using the "_rotation" property of a movie clip to determine the angle of the movie clip.
If you need to know the degrees of rotation as a factor of 360, a simple conversion code like that shown below will do the trick.
onClipEvent (enterFrame)
{
//This version uses multiplication so
//rotateIncrement cannot equal zero
if(this._rotation==0) {rotateIncrement=.1;}
//This code resets the max speed flag
if(rotateIncrement<=1) {accelFlag=1;}
//This code sets the max rotational
//speed shown here as 30 degrees per frame
//If max acceleration has occured the
//code resets the speed flag
if(rotateIncrement>30) {accelFlag=0;}
//This code sets the acceleration speed
if(accelFlag==1) {rotateIncrement=rotateIncrement*1.1;}
//Use rotateIncrement=rotateIncrement to
//maintain max speed
if(accelFlag==0) {rotateIncrement=.1;}//rotateIncrement;}
//Increment the rotational speed
this._rotation+=rotateIncrement;
}
This version accelerates the rotation steadily.
onClipEvent (enterFrame)
{
//This code resets the max speed flag
if(rotateIncrement<=1) {accelFlag=1;}
//This code sets the max rotational speed
//shown here as 15 degrees
//If max acceleration has occured the
//code resets the speed flag
if(rotateIncrement>15) {accelFlag=0;}
//This code sets the acceleration speed
if(accelFlag==1) {rotateIncrement+=.1;}
//This code resets rotational speed back to zero
//Use rotateIncrement=rotateIncrement to
//maintain max speed
if(accelFlag==0) {rotateIncrement=0;}//rotateIncrement;}
//Increment the rotational speed
this._rotation+=rotateIncrement;
}
This version accelerates then decelerates the rotation.
onClipEvent (enterFrame)
{
//This version uses multiplication so
//rotateIncrement cannot equal zero
if(this._rotation==0) {rotateIncrement=.1;}
//This code resets the acceleration
//flag to accelerate
if(rotateIncrement<=.1) {accelFlag=1;}
//20 sets the maximum speed
//If rotateIncrement reaches 20 the flag
//is set for deceleration
if(rotateIncrement>20) {accelFlag=0;}
//Increase the speed of rotation
if(accelFlag==1) {rotateIncrement=rotateIncrement*1.1;}
//Decrease the speed of rotation
if(accelFlag==0) {rotateIncrement=rotateIncrement*.9;}
//Rotate the movie clip
this._rotation+=rotateIncrement;
}
This version gives a trip hammer effect.
onClipEvent (enterFrame)
{
// Check to see if the clip is at zero rotation
// If it is, change it to one so that it can
//be multiplied
if(this._rotation==0) {rotateIncrement=1;}
//Set the flag for the downstroke
if(rotateIncrement<=1) {accelFlag=1;}
//Set the flag to bring the hammer back
//90 indicates the total degrees of movement the
//hammer will make before returning
if(rotateIncrement>90) {accelFlag=0;}
//Add acceleration to the downstroke
if(accelFlag==1) {rotateIncrement=rotateIncrement*1.1;}
//Bring the hammer back up
if(accelFlag==0) {rotateIncrement=rotateIncrement*.9;}
this._rotation=rotateIncrement;
}
