Issue with GLM Camera X,Y Rotation introducing Z R

So I've been having trouble with a camera I've implemented in OpenGL and C++ using the GLM library. The type of camera I'm aiming for is a fly around camera which will allow easy exploration of a 3D world. I have managed to get the camera pretty much working, it's nice and smooth, looks around and the movement seems to be nice and correct.

The only problem I seem to have is that the rotation along the camera's X and Y axis (looking up and down) introduces some rotation about it's Z axis. This has the result of causing the world to slightly roll whilst travelling about.

As an example... if I have a square quad in front of the camera and move the camera in a circular motion, so as if looking around in a circle with your head, once the motion is complete the quad will have rolled slightly as if you've tilted your head.

My camera is currently a component which I can attach to an object/entity in my scene. Each entity has a "Frame" which is basically the model matrix for that entity. The Frame contains the following attributes:

glm::mat4 m_Matrix;
glm::vec3 m_Position;
glm::vec3 m_Up;
glm::vec3 m_Forward;

These are then used by the camera to create the appropriate viewMatrix like this:

const glm::mat4& CameraComponent::GetViewMatrix()
{
    //Get the transform of the object
    const Frame& transform = GetOwnerGO()->GetTransform();

    //Update the viewMatrix
    m_ViewMatrix = glm::lookAt(transform.GetPosition(), //position of camera
                           transform.GetPosition() + transform.GetForward(), //position to look at
                           transform.GetUp()); //up vector

    //return reference to the view matrix
    return m_ViewMatrix; 
}

And now... here are my rotate X and Y methods within the Frame object, which I'm guessing is the place of the problem:

void Frame::RotateX( float delta )
{
    glm::vec3 cross = glm::normalize(glm::cross(m_Up, m_Forward)); //calculate x axis

    glm::mat4 Rotation = glm::rotate(glm::mat4(1.0f), delta, cross);

    m_Forward = glm::normalize(glm::vec3(Rotation * glm::vec4(m_Forward, 0.0f))); //Rotate forward vector by new rotation

    m_Up = glm::normalize(glm::vec3(Rotation * glm::vec4(m_Up, 0.0f))); //Rotate up vector by new rotation
}


void Frame::RotateY( float delta )
{
    glm::mat4 Rotation = glm::rotate(glm::mat4(1.0f), delta,  m_Up);    

    //Rotate forward vector by new rotation
    m_Forward = glm::normalize(glm::vec3(Rotation * glm::vec4(m_Forward, 0.0f))); 
}

So somewhere in there, there's a problem which I've been searching around trying to fix. I've been messing with it for a few days now, trying random things but I either get the same result, or the z axis rotation is fixed but other bugs appear such as incorrect X, Y rotation and camera movement.

I had a look at gimbal lock but from what I understood of it, this problem didn't seem quite like gimbal lock to me. But I may be wrong.

回答1:

Store the current pitch/yaw angles and generate the camera matrix on-the-fly instead of trying to accumulate small changes on the intermediate vectors.

回答2:

In your RotateY function, change it from this:

glm::mat4 Rotation = glm::rotate(glm::mat4(1.0f), delta,  m_Up);

to this:

glm::mat4 Rotation = glm::rotate(glm::mat4(1.0f), delta,  glm::vec3(0,1,0));