[Plib-users] OpenGL primitives

[Stafford G. <su...@ma...>]

Hi,

Im trying to debug some physics code i have, and i would like to draw a 
'force vector' (GL_LINE) indicating where the force is applied. However, when 
i do, it does not show. (Yes i did it between glBegin/glEnd pairs) I think it 
is because im also using the ssg library to draw the main scene.

Is it possible to draw using both OpenGL and ssg scenes at the same time?

Also, the reason i need to debug this code so intensely is because it seems 
that the axes are different depending on if you are rotating or translating... 
for translating x appears to be -, y is |, and z is . (into the screen), but 
for rotations, x is around |, y is around -, and z is the same. 
For example:

an object at (0, 0, 0):  
                                         -.
an object at (0, -2, 5):
                                              -.
an object at (0, -4, 0), rotated by (180, 0, 0):
                                         .-
                         .
the last one should be '- ' if the coordinate systems were the same.

Is this a bug in plib, or some strange 'feature' of OpenGL? I have tried both 
plib 1.0.20, and 1.1.11, and they are the same in this respect. This anomaly 
is giving me much trouble in creating rotations relative to an object (as one 
needs in physics). For example i can only get a helicopter to rotate around the 
global y axis (|) not its own y axis, which may be totally different.
See http://marys.dyndns.org/~surge/geome/ for some pictures of this.

Thanks for any help.

--
Stafford Goodsell  <su...@po...>                                     _
                                                                       C")
  Programmer, administrator, avid gamer and all-round computer geek    (_)
                 http://www.marys.dyndns.org/                          -"-