Re: [JAVA3D] local rotation possible?

[Lewis Walker]

Title: Message

Excuse the sketchy details, but I can point you in the right direction (I think). Ultimately, the translation / rotation etc. is encapsulated in a single Transformation between Local and World Coordinate Systems. This single Transformation, however, is obtained by traversing the scene graph from the root, all the way to your ship, and multiplying together all the Transform3Ds found along the way.   This is just normal maths - you can combine transformations represented by matrices, by performing matrix multiplication. However - Matrix multiplication is not commutative, which means that A x B does not equal B x A in general. i.e. a rotation followed by a translation is not the same as a translation followed by a rotation.   Could it be that you are post-multiplying your transformations, when it should be a pre-multiplication, or vice versa? I don't know whether you are even explicitly separating out your translation and rotation in the scene graph. If not, I probably would change it so that you are. It makes it easier conceptually, and Java3D will probably optimise it at runtime anyway, so you don't have to worry about an overhead.   Try parenting your ship with a Transform3D which is a rotation, and parenting that with a Transform3D which is a translation. (I might have that the wrong way round. If so - swap the rotation and the translation!). Then, you can change your rotations and translations independantly by setting the corresponding Transform3D.   Hope this helps. Lewis. -----Original Message----- From: Discussion list for Java 3D API [mailto:[EMAIL PROTECTED] On Behalf Of Johannes Neubauer Sent: 06 September 2003 16:55 To: [EMAIL PROTECTED] Subject: [JAVA3D] local rotation possible? Hi,   Here's the link: http://www.kingsware.de/j3d/gamerot.zip   I have a new problem. I update only the x- and y-rotation of my ship every Frame. It sets the rotation by looking at the Mouse position. But my ship rotates over all axis x,y AND z, but not at the same time!!! It looks like Java3D decides, which are the x and y axis from the viewplatforms point of view!! Is that right?   How can I set a "local"-Rotation, which rotates the local axis not the "viewed" one   I had the same problem, only the other way around, with Translation. The ship moved on the global axis instead of flying, depending on the ships current rotation.     I fixed this problem like this(not exactly): Code:   //Position   Vector3f position = new Vector3f(x,y,z);   Transform3D posTrans = new Transform3D();     //Rotation   Transform3D rotX3d = new Transform3D();   Transform3D rotY3d = new Transform3D();   Transform3D rotXY3d = new Transform3D();     //change the XY-Rotation (with MouseAngle)   rotX3d.rotX(xAngle);   rotY3d.rotY(yAngle);      rotXY3d.mul(rotX3d, rotY3d);     //The solution! now the positiontranslation is local!   rotXY3d.transform(position);     posTrans.set(position);   Is there any possibility to do this with rotation. There must be the possibility to rotate over the local axis! I've read something about the following function:   Code: view.getLocalToVWorld(Transform3D trans)   Is this a possibility? Anyone fixed this problem, yet Greets and thanks, Juan =========================================================================== To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff JAVA3D-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help". =========================================================================== To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff JAVA3D-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".

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