Clamp rotatation angle of a rigid body

Question

I recently attached a rigid body to the camera in my 3d game, so that it can collide with the environment. By now mouse movement directly rotates the rigid body.

#include <BULLET/btBulletDynamicsCommon.h>

void Rotate(float Pitch, float Yaw, float Roll, float Speed)
{
    // get current rotation
    btTransform transform = body->getWorldTransform();
    btQuaternion rotation = transform.getRotation();

    // create orientation vectors
    btVector3 up(0, 1, 0);
    btVector3 lookat = quatRotate(rotation, btVector3(0, 0, 1));
    btVector3 forward = btVector3(lookat.getX(), 0, lookat.getZ()).normalize();
    btVector3 side = btCross(up, forward);

    // rotate camera with quaternions created from axis and angle
    rotation = btQuaternion(up,      Amount.getY()) * rotation;
    rotation = btQuaternion(side,    Amount.getX()) * rotation;
    rotation = btQuaternion(forward, Amount.getZ()) * rotation;

    // set new rotation
    transform.setRotation(rotation);
    body->setWorldTransform(transform);
}

I would like to clamp the pitch of the camera in the range of -80° to 80°. That helps the player to stay oriented. Otherwise he would be able to rotate the camera higher over his head and see the world behind himself upside down. In contrast a real person trying this would break his neck.

I let Bullet Physics store rotations for me in quaternions, thus pitch isn't stored directly. How can I clamp the pitch of a rigid body?

Answer 1

I came up with a solution. Instead of clamping the rotation of the camera's rigid body, I clamp how much rotation is applied before. Therefore, I keep track of the total vertical mouse movement. Actually, I store the overall mouse movement with applied sensitivity.

float Overallpitch = 0.0f;

If applying the passed yaw value would result in the overall pitch to exceed or deceed a given limit, I just apply as much of it as needed to touch the limit.

#include <BULLET/btBulletDynamicsCommon.h>

void Rotate(float Pitch, float Yaw, float Roll, float Sensitivity)
{
    // apply mouse sensitivity
    Yaw   *= Sensitivity;
    Pitch *= Sensitivity;
    Roll  *= Sensitivity;

    // clamp camera pitch
    const float clamp = 1.0f;
    if     (Overallpitch + Pitch >  clamp) Pitch =  clamp - Overallpitch;
    else if(Overallpitch + Pitch < -clamp) Pitch = -clamp - Overallpitch;
    Overallpitch += Pitch;

    // apply rotation to camera quaternion
    // ...
}

You can find the further camera code in another answer to my own question.