Reactor.RCamera.RotateFirstPerson C# (CSharp) Method

        public void RotateFirstPerson(float headingDegrees, float pitchDegrees)
        {
            accumPitchDegrees += pitchDegrees;

            if (accumPitchDegrees > 90.0f)
            {
                pitchDegrees = 90.0f - (accumPitchDegrees - pitchDegrees);
                accumPitchDegrees = 90.0f;
            }

            if (accumPitchDegrees < -90.0f)
            {
                pitchDegrees = -90.0f - (accumPitchDegrees - pitchDegrees);
                accumPitchDegrees = -90.0f;
            }

            float heading = MathHelper.ToRadians(headingDegrees);
            float pitch = MathHelper.ToRadians(pitchDegrees);
            Quaternion rotation = Quaternion.Identity;

            // Rotate the camera about the world Y axis.
            if (heading != 0.0f)
            {
                Quaternion.CreateFromAxisAngle(ref WORLD_Y_AXIS, heading, out rotation);
                Quaternion.Concatenate(ref rotation, ref orientation, out orientation);
            }

            // Rotate the camera about its local X axis.
            if (pitch != 0.0f)
            {
                Quaternion.CreateFromAxisAngle(ref WORLD_X_AXIS, pitch, out rotation);
                Quaternion.Concatenate(ref orientation, ref rotation, out orientation);
            }
        }