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Author: Tim Murray | Website: http://www.gmg.com.au

What is the mouse doing over the image?

Let's find out! Open up your qtvr Movie Clip and select the driver Movie Clip. We're going to find out what our driver Movie Clip can do with the mouse. Let's do some testing.

Enter this code on the driver Movie Clip:

onClipEvent (enterFrame) {
     trace(_xmouse);
}

The trace command will write out its arguments (the bits in the parenthesis) to the Output window when you preview Flash MX movies. So: preview that (Ctrl+Enter) now. Notice that the _xmouse variable returns the x position of the mouse (left-right value) in relation to the Movie Clip that the code sits on (in this case it's the driver clip).

The reason we're doing this is that we want to somehow convert the position of the mouse to one of our QTVR movie frames (1 through to 36 for us). Our approach was to scale the driver movie. No matter how wide or narrow you make the driver clip, _xmouse will always return 0 to 100 when you move the mouse across it (because we made it with a shape that had a width of 100). Try stretching the driver clip and previewing the movie.

If we think of _xmouse as a percentage of rotation that we want the QTVR movie to go through, then the area of screen that we stretch it over will give us a visual indication of how much mouse movement we are expecting users to make to get a full rotation of the object.

Now we need to convert the 0 to 100 percentage to a fraction by dividing _xmouse by 100. If we multiply this by 36 (the number of frames we have – yours will be different) we will have the frame that we want to show. Try this new code and preview it:

onClipEvent (enterFrame) {
     trace(_xmouse / 100 * 36);
}

The Output window will show the frame that we should be displaying according to where the mouse is. Unfortunately, we are not getting exact frame numbers, so let's convert the number to an integer. Here's the code:

onClipEvent (enterFrame) {
     trace(int(_xmouse / 100 * 36));
}

That's better, but there's still some weirdness. The 1 to 36 is good: we have those frames. Anything out of that range is no use to us at all.

Time to roll out the modulo operator (%). When you use modulo, you get a remainder as a result. 4 % 2 gives remainder 0. 3 % 2 gives remainder 1. If we take our _xmouse calculation and do a modulo 36 we should get a remainder between 0 and 35. Add 1 and we have a good range of 1 to 36. Try it:

onClipEvent (enterFrame) {
     trace(int(_xmouse / 100 * 36) % 36 + 1);
}

Here are the formulas that we have been playing with so far (the box header in the table indicates the "invisible box" shape we made, and the shaded areas show where our 36 frames are repeating):

You can try them out in a trace ActionScript statement to see how they perform as you move your mouse over the QTVR movie to the right.

If you're interested, you can read more about the modulo operator here "ActionScript Dictionary > Symbols > % (modulo)", and the int function here "ActionScript Dictionary > G-L > int" in the contents of your online help. (I know int has been deprecated since Flash 5 in favour of the Math.round method, but round doesn't do what int does so I'm going to use it anyway!)

If you want to see how this will spin the movie, try this code:

onClipEvent (enterFrame) {
     _parent.gotoAndStop(1 + (int(_xmouse / 100 * 36) % 36));
}

We make use of the _parent object to do this. It refers to the parent of the Movie Clip in which the code is running. In other words, the parent Movie Clip of our driver clip is our qtvr clip. Have a look in the Movie Explorer (Alt+F3) to see how things relate to each other.

We are using _parent with the gotoAndStop method because without it, gotoAndStop would try to move the playhead of the driver Movie Clip, and that would be pointless 'cos the QTVR movie is in the qtvr Movie Clip (and that's just where we want it).

The info for gotoAndStop is here "ActionScript Dictionary > M > MovieClip.gotoAndStop" in the contents of your online help.

» Level Advanced

Added: 2003-12-16
Rating: 8 Votes: 76
(10 being the highest)
» Author
Tim is a co-director of the Glasson Murray Group, providing quality graphic design, illustration, 3D visualisation, interactive environments, virtual reality, multimedia and website services.
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