[gameprogrammer] Rotation, Rotation, Rotation...

  • From: "richard sabbarton" <richard.sabbarton@xxxxxxxxx>
  • To: gameprogrammer@xxxxxxxxxxxxx
  • Date: Mon, 17 Mar 2008 09:32:08 +0000

Hi Guys,

I have a problem and I am absolutely sure that I have missed something
obscenely obvious.  This is C++ with OpenGL/SDL.

In a 3D environment my player struct has 3 values for rotation around
x,y and z.  I want the player to be able to freely rotate around all 3
axis and I always want the mouse/joystick/keypad to operate the x and
y axis rotation.  When I initially move the mouse the rotation is
correct.  Left/Right and my scene rotates left and right.

If I rotate around z and then move the mouse my scene moves up and
down instead of left and right.  Now, I thought that all I needed to
do was change the order in which I rotated around each axis.  I
thought that if I rotated around Z first and then x and y after then
the movement of the mouse would always appear correct onscreen.  This
is what I call:

glRotatef(Player.ZRot,0.0f,0.0f,1.0f);  // Rotation around Z axis
glRotatef(Player.YRot,1.0f,0.0f,0.0f); // YRot is up and down around X axis
glRotatef(Player.XRot,0.0f,1.0f,0.0f); // XRot is left and right around Y axis


I thought that after performing the rotation the subsequent rotations
would be relative to the previous one.  So, if I rotate 90deg around Z
I thought it would then rotate relative to that effectivly switching
the x and y axis.  But it doesn't does it...

So I guess that is my question...  How do I perform a rotation and
then make all subsequent rotations relative to that initial rotation?

Regards

Richard

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