How to rotate (YAW) aircraft in XNA?

Question

I'm developing a flight simulator based on Riemer's Blog tutorial (XNA C#). To control the aircraft, I use the following code:

Quaternion additionalRotation = Quaternion.Identity;
additionalRotation *= Quaternion.CreateFromAxisAngle(Vector3.Forward, roll);
additionalRotation *= Quaternion.CreateFromAxisAngle(Vector3.Right, pitch);
model_ROTATION *= additionalRotation;

This only executes pitch and roll. I wanted to add code so that if the aircraft is rolling, then it should rotate to right or left (yaw) so I changed the code to the following:

Quaternion additionalRotation = Quaternion.Identity;
additionalRotation *= Quaternion.CreateFromAxisAngle(Vector3.Forward,roll);
additionalRotation *= Quaternion.CreateFromAxisAngle(Vector3.Up, yaw);
additionalRotation *= Quaternion.CreateFromAxisAngle(Vector3.Right, pitch);
model_ROTATION *= additionalRotation;

This behaviour is not so realistic; when I roll the aircraft rotates to right/left (yaws), but at the same time it loses altitude and I must pitch up (pull handle) to avoid crashing.

Is there any solution to make slew rotation (yaw) without losing altitude.

Answer 1

I avoid Euler angles in aircraft pitch, roll, yaw orientations because aircraft rotate about thier local axis and trying to resolve this to Euler angles about the world (or global) axis adds uneccesary complication to the code. Instead of 3 Euler angles, I store the current orientation as a matrix or quat and simply modify the matrix/quat depending on input since last frame. A matrix or a quat is equally sufficient but the matrix has the advantage of being in the same format that you need to send to the shader anyway and it has properties that are the exact axes you need to do the rotations about. A quat is useful if you want steady slerp rates. Gimbal lock is absolutly NOT an issue when working with matrices this way.

//class scope variables
Matrix aircraftOrientationMatrix = Matrix.Identity;
float pitchChangeThisFrame, yawChangeThisFrame, rollChangeThisFrame;

//in the Update method
pitchChangeThisFrame = ?.f;//actual value based on player input
yawChangeThisFrame = ?.f;
rollChangeThisFrame = ?.f;

Vector3 pitch = aircraftOrientationMatrix.Right * pitchChangeThisFrame;//local pitch axis * amount of pitch change to apply this frame
Vector3 yaw = aircraftOrientationMatrix.Up * yawChangeThisFrame;
Vector3 roll = aircraftOrientationMatrix.Forward * rollChangeThisFrame;

Vector3 overallOrientationChangeThisFrame = pitch + yaw + roll;//
float overallAngularChangeThisFrame = overallOrientationChangeThisFrame.Length();//magnitude of all changes added together
Vector3 overallRotationAxis = Vector3.Normalize(overallOrientationChangeThisFrame);

Matrix orientationChangeThisFrame = Matrix.CreateFromAxisAngle(overallRotationAxis, overallAngularChangeThisFrame);

aircraftOrientationMatrix *= orientationChangeThisFrame;

Answer 2

You're using vector3.up, vector3.forward and vector3.right to calculate the needed rotations. These axes don't move along with your plane. What you need to do is rotate the plane around its very own up, forward and right vectors. You could do that like this:

Matrix rotMat = Matrix.CreateFromQuaternion(model_ROTATION);
Quaternion additionalRotation = Quaternion.Identity;
additionalRotation *= Quaternion.CreateFromAxisAngle(rotMat.Forward,roll);
additionalRotation *= Quaternion.CreateFromAxisAngle(rotMat.Up, yaw);
additionalRotation *= Quaternion.CreateFromAxisAngle(rotMat.Right, pitch);
model_ROTATION *= additionalRotation;