(Ok, this is for C++ 3D OpenGL programmers =) )

Rotating the Camera
-------------------

Well, I've decided to share some knowledge to anyone who know C++ and is having trouble with their 3D camera or anything, here's just my own techniques and theory.

There are a few things you need to know, I use OpenGL which has a 4x4 matrix it works on. So the Rotation Matrices are like this:

PITCH (x-axis)
-----
| 1 0 0 0|
| 0 cos(theta) -sin(theta) 0|
| 0 sin(theta) cos(theta) 0|
| 0 0 0 1|

YAW (y-axis)
---
| cos(theta) 0 sin(theta) 0|
| 0 1 0 0|
|-sin(theta) 0 cos(theta) 0|
| 0 0 0 1|

ROLL (z-axis)
----
| cos(theta) -sin(theta) 0 0|
| sin(theta) cos(theta) 0 0|
| 0 0 1 0|
| 0 0 0 1|
-----------------------------------

Well, those are the basic rotation methods for a 3D camera, hehe, some real Quake 3 knowledge right there. Now, to make things work you'll need some definitions.

----------------------------------------
#define PI (3.14159265359)
#define DEG2RAD(a) (PI/180*(a))
#define RAD2DEG(a) (180/PI*(a))

typedef float scalar_t // your scalar
----------------------------------------
________________________________________
Now, for the 3D camera movement code :-D|
-----------------------------------------
void CCameraCV::Animate(scalar_t deltaTime)
{
// You can do some calculations for the pitch,yaw, and roll
float cosYaw = (scalar_t)cos(DEG2RAD(yaw));
float sinYaw = (scalar_t)sin(DEG2RAD(yaw));
float sinPitch = (scalar_t)sin(DEG2RAD(pitch));

// speed on the z axis
float speed = velocity.z * deltaTime;

// friction
if (velocity.Length() > 0.0)
acceleration = -velocity * 1.5f;
velocity += acceleration*deltaTime;

// Calc the 3D Camera position
position.x += float(cos(DEG2RAD(yaw + 90.0)))*strafeSpeed;
position.z += float(sin(DEG2RAD(yaw + 90.0)))*strafeSpeed;
position.x += float(cosYaw)*speed;
position.z += float(sinYaw)*speed;

// Calc the 3D Camera rotation
lookAt.x = float(position.x + cosYaw);
lookAt.y = float(position.y + sinPitch);
lookAt.z = float(position.z + sinYaw);

gluLookAt(position.x, position.y, position.z,
lookAt.x, lookAt.y, lookAt.z,
0.0, 1.0, 0.0);
}

DONE! That's it! This code is good enough for Quake 4! Now that wasn't so hard huh. Hope this gives light to any C++ 3D programmer out there.