x-y-z angles...

Does anybody know how to derive the x y and z angles between two points?

Thanks,

Devin

 

You'll have to be a bit more explicit. How would you define, for example,
the "x angle" between two points?
___

 

Exactly. I was wondering if anybody had any formulas for geting the x angle
between two points and, seperately, the y angle between two points and also
the z angle between two points. I'm trying to define a rotation matrix. I
could use trig, ie...

for angle of point in the xy plane

(defun xy_ang ( pt )
(atan (/ (cadr pt) (car pt)))
)

But I could see divide by zero errors and such and what about the sign? How
do you acout for divide by zero errors?

Devin

 

Devin,
xy angle is a lot different than the angle from the x axis.

To determine the angle of a point from a single axis, you
need to think in the plane that contains the point, the
origin, and a point on the axis. Transforming the
point to the ucs that contains those three points would
give you an x,y pair that could be used with the
angle function. You can do UCS transformations
without having autocad actually make the UCS active
by using ActiveX to add the ucs and getucsmatrix and
transformby to get the points.

Mathematically you could do the same things. If I were
looking for that solution, I'd be searching on google or
in math areas.

What on earth do you use all this stuff for?

Regards,
Doug

 

Like I said: what do you mean by the "x angle"???
___

 

I've created, with help, transformation routines to deal with transformation
matrices. Rotational transformation matrices to be more precise. The exact
same ones returned by active-x. Everything works great, and I'm learning
alot about transformations. But I would like to create my own
transformation matrix, bypassing autocad's active-x server altogether.
given a plane, I need to determine the x y and z angles of that plane to
create the transformation matrix.

I was hoping that someone had some code I could look at to try to understand
how to get the angles. I've got three points, an origin, xvector and
yvector.

Thanks,

Devin

 

Hi Paul,

What I mean by x angle is the rotation of a point about the x axis. For the
y and z axis as well.

Thanks,

Devin

 

Thanks Bill.



 



Devin