3D Camera Rotation

[Lumooja]

I can't get the camera to rotate around itself.

The X-axis rotation works fine.
The Y-axis rotation does not rotate around the camera, but around the world's Y-axis?
Also, when I rotate around the Z-axis, it seems to rotate also around something else than the camera's Z-axis.

I added Z-axis rotation to simple1.cpp like this:

// We now assign a new rotation transformation to the camera.  You
  // can think of the rotation this way: starting from the zero
  // position, you first rotate "rotY" radians on your Y axis to get
  // the first rotation.  From there you rotate "rotX" radians on the
  // your X axis to get the final rotation.  We multiply the
  // individual rotations on each axis together to get a single
  // rotation matrix.  The rotations are applied in right to left
  // order .
  csMatrix3 rot = csXRotMatrix3 (rotX) * csYRotMatrix3 (rotY) * csZRotMatrix3 (rotZ);
  csOrthoTransform ot (rot, c->GetTransform().GetOrigin ());
  c->SetTransform (ot);

[jorrit]

Try inverting the rotation matrices.

Greetings,

[Lumooja]

Thanks, that was new to me.

I tried the following:

  csMatrix3 rot = csXRotMatrix3 (rotX).GetInverse() * csYRotMatrix3 (rotY).GetInverse() * csZRotMatrix3 (rotZ).GetInverse();
  csOrthoTransform ot (rot.GetInverse(), c->GetTransform().GetOrigin ());

It seems to fix the Y-axis rotation (cursor left/right) when X-axis is turned, however when I rotate around the Z-axis, the X and Y axis are now rotating around the world's X/Y-axises always.

Don't I need to set the UpVector each time the camera is turned (and how would I calculate this), or can this be done somehow with this inversing matrices trick?

Hmm, now the iCamera class doesn't seem to have .SetUp() and .SetLookAt() methods.

Ahh, iModelDataCamera has .SetUpVector() and .SetFrontVector() (sounds like this could be the same as .SetLookAt() in other engines) methods, but <mdldata.h> which has iModelCamera is missing now.

[Lumooja]

Yes! I found it!

No need for any matrix operations at all. I watched the Cassini Division movie and those guys had a web site at the end of the movie, there I found cassini.cpp and this simple code to rotate the camera in real 3D manner (I added Z-axis rotation though):

   // handle keyboard input... asynchronously, I guess
   if(kbd->GetKeyState(CSKEY_RIGHT))   c->GetTransform().RotateThis(CS_VEC_ROT_RIGHT, speed);
   if(kbd->GetKeyState(CSKEY_LEFT))   c->GetTransform().RotateThis(CS_VEC_ROT_LEFT, speed);
   if(kbd->GetKeyState(CSKEY_PGUP))   c->GetTransform().RotateThis(CS_VEC_TILT_UP, speed);
   if(kbd->GetKeyState(CSKEY_PGDN))   c->GetTransform().RotateThis(CS_VEC_TILT_DOWN, speed);
   if(kbd->GetKeyState(CSKEY_DEL))      c->GetTransform().RotateThis(CS_VEC_TILT_LEFT, speed);
   if(kbd->GetKeyState(CSKEY_END))      c->GetTransform().RotateThis(CS_VEC_TILT_RIGHT, speed);
   if(kbd->GetKeyState(CSKEY_UP))      c->Move(CS_VEC_FORWARD * 4 * speed);
   if(kbd->GetKeyState(CSKEY_DOWN))   c->Move(CS_VEC_BACKWARD * 4 * speed);

Now my modified appsimple1.cpp works perfectly, and I can focus on the next steps with Crystal Space.
These original lines were totally useless for my needs, and so I commented them out:

// csMatrix3 rot = csXRotMatrix3 (rotX) * csYRotMatrix3 (rotY) * csZRotMatrix3 (rotZ);
// csTransform ot (rot, c->GetTransform().GetOrigin());

Btw, The Cassini Division is an awesome game - I love the realistic thruster sounds! Beats any commercial space game