quote:Original post by LockePick
He means he needs the calculations for figuring out the rotation values, no matter what the 2 points are. You can''t just glRotate(90,0,1,0) to get from u(372, 832.63, 93) to (0, 342, 20.04)

There''s some trig stuff involved with that. I lost the function I used to use for this sort of stuff. I think it was something like float yRot = atan( u(x1), v(x2) ); glRotatef(yRot, 0, 1, 0); and then you''d repeat it for the other axis. I''ll edit this if I can remember better or get around to trying it out.

Sorry I can''t offer anything else, perhaps someone older who actually knows this stuff properly can help you.

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  y            z  ^            ^  |   B        |  |  /         |  B  | /          | /  |A           |A  +---->x      +---->x

    float angleY;float angleZ;// calculate angleYif (By - Ay == 0)   angleY = PI / 2;else   angleY = atan((Bx - Ax) / (By - Ay));if (By - Ay < 0)   angleY += PI;// calculate angleZif (Bz - Az == 0)   angleZ = PI / 2;else   angleZ = atan((Bx - Ax) / (Bz - Az));if (Bz - Az < 0)   angleZ += PI;// apply rotations// this should rotate around Z-axisglRotatef(angleY, 0, 0, 1);// this should rotate around Y-axisglRotatef(angleZ, 0, 1, 0);    

quote:Original post by j p
1) Don''t use auxSolidCylinder or any aux functions from the glaux library. See "Don''t use the glaux" at http://www.mfcogl.com/

2) I put up a tutorial and demo with source code exactly about what you want to do, drawing cylinder between two points at

http://www.mfcogl.com/OpenGL%20-%20draw%20cylinder%20between%202%20pts.htm

It is in MFC but all the OpenGL code is valid. Just cut and paste in the framework of your choice, but please pass the word and get rid of the glaux header.

quote:Original post by Enigma
Well, I''ll have a go (can''t promise this''ll work)

We have points A and B and want a cylinder to connect the two points. Assumin CA and CB are the central points of the two ends of the cylinder then:

  y            z  ^            ^  |   B        |  |  /         |  B  | /          | /  |A           |A  +---->x      +---->x 

(diagrams to help me figure this out)
angle between AB and y-axis = atan((Bx - Ax) / (By - Ay)).
angle between AB and z-axis = atan((Bx - Ax) / (Bz - Az)).

You''ll also be affected by quadrants:

first quadrant ((Bx - Ax) >= 0, (By - Ay) >= 0):
angle between AB and y-axis = atan((Bx - Ax) / (By - Ay)).

second quadrant ((Bx - Ax) >= 0, (By - Ay) < 0):
angle between AB and y-axis = PI + atan((Bx - Ax) / (By - Ay)).

third quadrant ((Bx - Ax) < 0, (By - Ay) < 0):
angle between AB and y-axis = PI + atan((Bx - Ax) / (By - Ay)).

fourth quadrant ((Bx - Ax) < 0, (By - Ay) >= 0):
angle between AB and y-axis = (2 * PI) + atan((Bx - Ax) / (By - Ay)).

(also for z axis)

So, to rotate the cylinder correctly to join A(Ax, Ay, Az) and B(Bx, By, Bz):

      float angleY;float angleZ;// calculate angleYif (By - Ay == 0)   angleY = PI / 2;else   angleY = atan((Bx - Ax) / (By - Ay));if (By - Ay < 0)   angleY += PI;// calculate angleZif (Bz - Az == 0)   angleZ = PI / 2;else   angleZ = atan((Bx - Ax) / (Bz - Az));if (Bz - Az < 0)   angleZ += PI;// apply rotations// this should rotate around Z-axisglRotatef(angleY, 0, 0, 1);// this should rotate around Y-axisglRotatef(angleZ, 0, 1, 0);