Second Life Forums Archive - Rotation around edge not axis

Haruki Watanabe

llSLCrash(void);

Join date: 28 Mar 2007

Posts: 434

05-29-2007 05:42

OK - I found TONS of scripts 'n hints about rotation - but every script I found always rotated the object around the center of the object.
But I need to rotate it around the edge. Say, I hava a box and now want to rotate that box around a corner of the box. AND - and this is the problem: without linking the box to another prim (which would be the easiest way, then I just rotate the small attached prim and thus the box would rotate with it...)...

Hope I wasn't to vague...

Thanks for every hint in advance!

White Hyacinth

Registered User

Join date: 15 Nov 2006

Posts: 353

05-29-2007 06:12

What you need to do is make your box smaller with the path cut settings in the edit box. This will make it look like it rotates on the edge.

Haruki Watanabe

llSLCrash(void);

Join date: 28 Mar 2007

Posts: 434

Cool!

05-29-2007 06:26

Thanks a lot - sounds like a good idea! I'll try that!

))

Lyn Mimistrobell

(waiting)

Join date: 11 Jan 2007

Posts: 179

05-29-2007 07:03

Sometimes you can't use a cut (depending on the shape of the object you want to rotate) in which case you can use a combination of llSetPos and llSetRot (or together in an llSetPrimitiveParams) to make it look like it rotated on a different virtual axis. It won't look as good as a normal rotation but the endresult will be ok.

Haruki Watanabe

llSLCrash(void);

Join date: 28 Mar 2007

Posts: 434

thanks again

05-29-2007 08:00

I thought of this as well, but actually feared the math I'd have to do to compute the new location depending on the rotation and the size of the prim... I'm sure there's a way though... and I hope I'll figure out...

Newgate Ludd

Out of Chesse Error

Join date: 8 Apr 2005

Posts: 2,103

05-29-2007 08:23

From the wikki

From: wikki

Combining Rotations
An object is rotated by multiplying its current orientation with the desired rotation. The order in which the operands are specified depends if a rotation is performed around the global axes or the local axes.

Example:
// a rotation of 45 degrees around the x-axis
rotation x_45 = llEuler2Rot( <45 * DEG_TO_RAD, 0, 0> );

rotation new_rot = llGetRot() * x_45; // compute global rotation
llSetRot(new_rot); // orient the object accordinglyThis rotates the object around the global x-axis (the axis which runs from west to east).

Now consider the following:
rotation new_rot = x_45 * llGetRot(); // compute local rotation
llSetRot(new_rot); // orient the object accordinglyThis rotates the object around its local x-axis, which depends on its current orientation. Think of this as specifying the rotation from the object's point of view, that is, relative to the direction it is currently facing.

This also works Inversely by Dividing two rotations:
rotation new_rot = x_45 / llGetRot(); // compute local rotation
llSetRot(new_rot); // orient the object accordinglyLike previously, this would rotate your object along the x-axis based on its current orientation, but in the opposite direction.

When rotating a vector, the rotation must appear to the right of the vector:
vector new_vec = old_vec * x_45; // compiles
vector new_v = x_45 * old_v; // doesn't compile
Note: An object can be rotated around an arbitrary point by multiplying a vector by a rotation in the manner described above. The vector should be the difference between the object's current position and the desired "center-point" of rotation. Take the result of the multiplication and add it to the point of rotation. This vector will be the "new location" the object should be moved to.

_____________________

I'm back......

Dnali Anabuki

Still Crazy

Join date: 17 Oct 2006

Posts: 1,633

05-29-2007 09:20

There is a way to change the axis to the edge of a rectangle.
Rez a sphere. Size 1, .120, 1. Dimple B. .500, E 1.00. Change sphere to box and axis should be to the edge now. Put in rotation script and it will turn on the edge with some script fiddling. Saves a prim anyway and great for doors.

Haruki Watanabe

llSLCrash(void);

Join date: 28 Mar 2007

Posts: 434

Helped!

05-30-2007 03:57

I well read this wikki-entry, but honestly... I didn't get it... (maybe I should go a little deeper into vectors 'n stuff...

The last entry with rezzing a sphere and fumbling around with dimple and then change it to a box helped and works perfectly...

Thanks a lot to all of you!

Bloodsong Termagant

Manic Artist

Join date: 22 Jan 2007

Posts: 615

05-30-2007 08:44

heyas;

there's my edge rotation function if you really, really, desperately, absolutely need to rotate around an edge.

/54/85/170765/1.html

_____________________

Why Johnny Can't Rotate:
http://forums.secondlife.com/showthread.php?t=94705

Rotation around edge not axis
Haruki Watanabe llSLCrash(void); Join date: 28 Mar 2007 Posts: 434	05-29-2007 05:42 OK - I found TONS of scripts 'n hints about rotation - but every script I found always rotated the object around the center of the object. But I need to rotate it around the edge. Say, I hava a box and now want to rotate that box around a corner of the box. AND - and this is the problem: without linking the box to another prim (which would be the easiest way, then I just rotate the small attached prim and thus the box would rotate with it...)... Hope I wasn't to vague... Thanks for every hint in advance!
White Hyacinth Registered User Join date: 15 Nov 2006 Posts: 353	05-29-2007 06:12 What you need to do is make your box smaller with the path cut settings in the edit box. This will make it look like it rotates on the edge.
Haruki Watanabe llSLCrash(void); Join date: 28 Mar 2007 Posts: 434	Cool! 05-29-2007 06:26 Thanks a lot - sounds like a good idea! I'll try that! ))
Lyn Mimistrobell (waiting) Join date: 11 Jan 2007 Posts: 179	05-29-2007 07:03 Sometimes you can't use a cut (depending on the shape of the object you want to rotate) in which case you can use a combination of llSetPos and llSetRot (or together in an llSetPrimitiveParams) to make it look like it rotated on a different virtual axis. It won't look as good as a normal rotation but the endresult will be ok.
Haruki Watanabe llSLCrash(void); Join date: 28 Mar 2007 Posts: 434	thanks again 05-29-2007 08:00 I thought of this as well, but actually feared the math I'd have to do to compute the new location depending on the rotation and the size of the prim... I'm sure there's a way though... and I hope I'll figure out...
Newgate Ludd Out of Chesse Error Join date: 8 Apr 2005 Posts: 2,103	05-29-2007 08:23 From the wikki From: wikki Combining Rotations An object is rotated by multiplying its current orientation with the desired rotation. The order in which the operands are specified depends if a rotation is performed around the global axes or the local axes. Example: // a rotation of 45 degrees around the x-axis rotation x_45 = llEuler2Rot( <45 * DEG_TO_RAD, 0, 0> ); rotation new_rot = llGetRot() * x_45; // compute global rotation llSetRot(new_rot); // orient the object accordinglyThis rotates the object around the global x-axis (the axis which runs from west to east). Now consider the following: rotation new_rot = x_45 * llGetRot(); // compute local rotation llSetRot(new_rot); // orient the object accordinglyThis rotates the object around its local x-axis, which depends on its current orientation. Think of this as specifying the rotation from the object's point of view, that is, relative to the direction it is currently facing. This also works Inversely by Dividing two rotations: rotation new_rot = x_45 / llGetRot(); // compute local rotation llSetRot(new_rot); // orient the object accordinglyLike previously, this would rotate your object along the x-axis based on its current orientation, but in the opposite direction. When rotating a vector, the rotation must appear to the right of the vector: vector new_vec = old_vec * x_45; // compiles vector new_v = x_45 * old_v; // doesn't compile Note: An object can be rotated around an arbitrary point by multiplying a vector by a rotation in the manner described above. The vector should be the difference between the object's current position and the desired "center-point" of rotation. Take the result of the multiplication and add it to the point of rotation. This vector will be the "new location" the object should be moved to. _____________________ I'm back......
Dnali Anabuki Still Crazy Join date: 17 Oct 2006 Posts: 1,633	05-29-2007 09:20 There is a way to change the axis to the edge of a rectangle. Rez a sphere. Size 1, .120, 1. Dimple B. .500, E 1.00. Change sphere to box and axis should be to the edge now. Put in rotation script and it will turn on the edge with some script fiddling. Saves a prim anyway and great for doors.
Haruki Watanabe llSLCrash(void); Join date: 28 Mar 2007 Posts: 434	Helped! 05-30-2007 03:57 I well read this wikki-entry, but honestly... I didn't get it... (maybe I should go a little deeper into vectors 'n stuff... The last entry with rezzing a sphere and fumbling around with dimple and then change it to a box helped and works perfectly... Thanks a lot to all of you!
Bloodsong Termagant Manic Artist Join date: 22 Jan 2007 Posts: 615	05-30-2007 08:44 heyas; there's my edge rotation function if you really, really, desperately, absolutely need to rotate around an edge. /54/85/170765/1.html _____________________ Why Johnny Can't Rotate: http://forums.secondlife.com/showthread.php?t=94705

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Rotation around edge not axis