It looks like the rotation matrix math in dada.h is inconsistent; and the signs on the sins need to be flipped for the y-axis.
I'm gonna make the change locally. This is an interesting one, since people probably depend on the existing behavior - but I'm pretty sure that behavior is incorrect! On Thu, Mar 19, 2009 at 6:04 PM, Scott <[email protected]> wrote: > OK - here's another one that has me scratching my head - and this time > I looked in the bug tracker before posting. > > As far as I can tell - we're a right handed coordinate system, which means: > > y > | > | > z-------x > > Where the "z" above is coming out of the screen. > Positive rotations about an axis mean COUNTER-CLOCKWISE (or > anti-clockwise if you speak British) rotations. That is, 1) rotating > 45 degrees about x, should push the y-axis in to the +y,+z quadrant > and 2) rotating 45 degrees about z should push the x-axis into the the > +x,+y quadrant and 3) rotating 45 degrees about y should push the > z-axis in to the +z +x quadrant. > > Well, doing a little checking, this is what I see: > > 1) X - puts y-axis +y, +z quad and puts z-axis -y, +z (AS EXPECTED) > 2) Z - puts x-axis +x, +y quad puts y-axis -x, +y quad (AS EXPECTED) > 3) Y - puts x-axis +x, +z quad puts z-axis -x, +z quad (???????? - BACKWARDS) > > It has been something like 10 years since I've done any 3D graphics so > it's possible I'm missing something very basic! > > ?? >
