Rotating 3D and keeping everything happy.

[Qube]

At the moment if you rotate a 3D object like so :

Code (glbasic) Select Expand


// EXAMPLE 1

x_movement x,y,z
x_rotation rotx, 1, 0, 0
x_rotation roty, 0, 1, 0
x_rotation rotz, 0, 0, 1
x_drawobj cube, 0


We suffer from gimbal lock (is that the correct term)? - For example you can't set the object to point upwards and rotate on the Y axis and keep rotating on the X axis perfectly while manipuating y or z rotations, BUT if we do something like :

Code (glbasic) Select Expand


// EXAMPLE 2

x_movement x, y, z
x_rotation rotx, 1, 0, 0
x_pushmatrix
   x_rotation roty, 0, 1, 0
   x_rotation rotz, 0, 0, 0
   x_drawobj cube, 0
x_pushmatrix


We can achieve the desired rotation of our object. We can then use x_getmatrix after the x_drawobj to get the coordinates of said object.

My question is this : How do I get the real angles rotx, roty, rotz from example 2 so I can draw other objects using the method in example 1?  I can't base the other objects inside the original push / pop matrix as they also get changed when the original object changes rotation, I need to be able to grab the x, y, z & the rotation angles for reuse.

I'm not sure if there are other bits from the output of x_getmatrix that I can use? I've looked but the don't seem to make much sense on how to use them apart from mat[12] / 13 & 14 which are the objects x,y,z.

Bit of a messy question but I think it makes sense?

[Qube]

um, ignore the above post, it's a load of messed up junk, lol

The only way to get rid of gimbal lock is to re-write all the rotation routines to use quaternions. I've no idea what they are and how they work (yet)  but they will solve the problem with GLBasics eular angles and good old gimbal lock.

Right, where did I leave my reading glasses, six pack of beer and thinking cap?

[Hatonastick]

Hmm that's odd.  I just did a search for "Quaternion" and got no results, and yet I'm positive someone (maybe Hemlos) was working on such a thing.

Edit:  Egads...  5 minutes reading Wikipedia entries on Gimbal Lock, Euler Angles and Quaternion's and my head is spinning from all this math-ey stuff!

[Hatonastick]

....  I just did a search for "Quaternion" and got no results, .....

Have you checked this board http://www.glbasic.com/forum/index.php?board=29.0  ?
It's even sticky!

Ocean

Gah!  Ok... As the females in my family put it: "I did a male look."