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Re: 3D Ball

To: REALbasic Games <realbasic-games at lists dot realsoftware dot com>
Subject: Re: 3D Ball
From: "Joseph J. Strout" <joe at realsoftware dot com>
Date: Wed, 21 Sep 2005 11:09:06 -0600
Delivered-to: realbasic-games at lists dot realsoftware dot com
References: <BF57078A dot EF94%larsjensen at rcn dot com>
At 12:50 PM -0400 9/21/05, Lars Jensen wrote:

 > To recap: move the ball, not the camera, and set the camera position using
 mSphere.ObjectToWorldTransform.

But he wants the ball to appear to roll. If he uses Pitch to do that, won't
it screw up ObjectToWorldTransform, and any Yawing he does subsequently to
change heading?

Aha, good point.

I would think that the simplest way to get the effect he wants -- which I
interpret as a "follow me" view of a rolling ball -- is in each frame, to
reset the ball's orientation, Yaw it to agree with the ball's current
heading, set the camera position from the ball's resulting orientation, and
then Pitch the ball some amount. The heading and Pitch from the last frame
would be remembered and the new values would be deltas on that.

Another way would be to put the ball inside a Group3D. Move the ball forward by moving the group; turn it by yawing the group. Make it roll by pitching the ball, not the group; and get the camera position by calling ObjectToWorldTransform on the group, not the ball.

Best,
- Joe

--
Joe Strout                          REAL Software, Inc.

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