[Plib-users] Bug in sgHPRfromVec3?

[Jon <jtw...@ih...>]

I'm currently tinkering with an app using the PLIB library which I have
found to be quite useful so far, however I have found on problem which I
think is a bug with the library.
I am using the sgHPRfromVec3 function to produce a camera orientation to
view my model.  It works well as long as my model and the camera are the
same height above the terrain but as soon as the relative height changes
the camera pitches off in the wrong direction.

here is the appropriate code snippet (scan is the current position of
the object, track is the camera position):

	sgSubVec3(temp, scan, track);	
	sgHPRfromVec3(scan,temp);
	sgSetCoord (&campos, track , scan);

if I add the following line between the second and third lines the
camera will track correctly.

	scan[1] = - scan[1];

I'm not sure if this is a problem with my code or a problem with the
Plib library, certainly changing the version didn't seem to affect the
behaviour.  I would be grateful for any light that could be shed on the
matter.


Jonathan Wheare.