Cameras - Game Programming Algorithms and Techniques - page 209

Vector3 target = eye + targetOffset
// For y-up world
Vector3 up = Vector3 (0, 1, 0)
cameraMatrix = CreateLookAt( eye , target , up )

end

// Updates based on the incremental yaw/pitch
angles for this frame
function Update( float yaw , float pitch )
totalYaw += yaw
totalPitch += pitch

// Clamp the total pitch based on restric-

tions

// In this case, 45 degrees (approx 0.78 rad)
totalPitch = Clamp( totalPitch , -0.78, 0.78)

// The target offset is before any rotations,
// actual is after rotations.
Vector3 actualOffset = targetOffset

// Rotate actual offset about y-up for yaw
Quaternion quatYaw = CreateFromAxisAngle(
Vector3 (0,1,0),

totalYaw )

actualOffset = Transform( actualOffset ,
quatYaw )

// Calculate left for pitch
// Forward after yaw just the actualOffset
(normalized)
Vector3 forward = actualOffset
forward .Normalize()
Vector3 left = CrossProduct( Vector3 (0, 1, 0),
forward )
left .Normalize()

// Rotate actual offset about left for pitch