I want to understand rotation parameters

Hi, I am guessing that the parameters represent an equivalent "roll about X-axis", "pitch about Y-axis" and "yaw about z-axis" that summarizes any number of individual elemental rotations about the axises; but, I can't figure it out exactly. For precision fitting I want to calculate the rotation parameters I need from the dihedral angles of various polyhedrons.

Can someone explain exactly what the parameters mean? If it is a pitch, roll & yaw coordinate system, what is the order of the operations?
Thanks, Craig Hilbert.

The three rotations you see in the rotation box normally represent rotation around the 3 axes of the world. If you use the pull-down box to change to the Local coordinate system then the rotations change to represent roll, pitch, and yaw.

The rotations are applied in the order you apply them; if you change the coordinates by typing directly into the dialog box, each rotation is changed at the time you move away from the field on the box. Within SL's internal database, the rotation of every object is stored as a single quaternion so rotation order is not relevant.

Hi Yumi, thanks for your reply. I guess I'm a real dunce, but I'm still confused. The rotations just don't seem to work as advertised! For instance, I experimented by rotating a half-cylinder. For ease of speaking, using the local coordinates I think of the red X-axis as yaw, the green Y-axis as pitch and the blue Z-axis as roll (the half-cylinder resembles a space vehicle pointing into the sky). Now, I first set the Y parameter to pitch 60 degrees to get the vehicle pointing more level; then I click on the ground and back to the prim to reset the axes to the vehicle's orientation. Now I try to yaw 30 degrees by setting the X axis; but, it seems to roll 30 degrees instead (as if I had set the Z-axis rather than the X-axis). Can you staighten me out? Thanks for your infinite patience.
Craig

From my experience, different prims seem to be created differently (X,Y,Z sometimes are different)

Can't you just hit the ctrl key to verify which axis you're looking to adjust? Then edit it accordingly in the edit box?

Craig -

The rotations in SL can be a bit weird, especially if you go over 90 degrees on more than 1 axis.

Now, it sounds like you are confusing the rotation reference. The numbers in the edit dialog are _always_ local. So, is you rotation the Y axis to 45 degrees, then rotate the Z axis 30 degrees, it is not going to rotate in relation to global coordinations (i.e, X and Y parellel to the ground) but to the current axis of the prim.

Um, I hope this helped.. If it didn't give me a shout in world, I'll see if I can help you.

I think I understand now, but I haven't had time to fully check it out. I think the rotation parameters represent the equivalent yaw-pitch-roll motion relative to the original coordinate system, with the Z-roll first, Y-pitch second and X-yaw third. Even if you rotate around different axes a dozen times, the parameters reflect just the equivalent three rotations about the original axes in the above order.

Does anyone know if that is correct?
Thanks!
Craig

it sounds like your using the world axis
try changing it to local axis
-LW

Hi Lightwave, I do have the coordinate system set to "local", so that does not seem to be my problem.

I am using a mathematics scratch pad (MathCAD) to multiply rotation matrices and to try to get the equivalent sl rotation parameters. My plan is to create polyhedrons, like an icosahedron, icosadodecahedran, etc.. Eventually, I think it would be neat to create alternative worlds, ala M. C. Escher. But I'm not to first base yet. Still, its great fun to dream!