In this code I'm assuming you want to work with a flat-XZ rotation. You can also do this with a flat-YZ or a flat-XY rotation, but then you will need to use quaternion.getPitch() or quaternion.getRoll().

Also be careful because I think it will not return a value between 90 & -90 but 0 & 180, so then you will need the edit the part where I check for the camera direction.

// Get CamDirection and cancel out Y-Axis and Magnitude Vector3 vCamDirection = mCamera->getDerivedOrientation() * Vector3::NEGATIVE_UNIT_Z; vCamDirection.y = 0; vCamDirection.normalise(); // Get rotations to X-Axis & Z-Axis Quaternion qRotationToXAxis = vCamDirection.getRotationTo( Vector3::UNIT_X ); Quaternion qRotationToZAxis = vCamDirection.getRotationTo( Vector3::UNIT_Z ); // Get the degrees from both rotations Real rRotationToXAxis = qRotationToXAxis.getYaw().valueDegrees(); Real rRotationToZAxis = qRotationToZAxis.getYaw().valueDegrees(); Real rRotation = 0; // Check which direction the camera is looking // And adjust rRotation if needed if( rRotationToXAxis >= 0 ) { rRotation = rRotationToZAxis; } else { if( rRotationToZAxis >= 0 ) { rRotation = rRotationToZAxis - rRotationToXAxis * 2; } else { rRotation = rRotationToZAxis + rRotationToXAxis * 2; } } // Rotate Texture TextureUnitState *texture = eCamView->getMaterial()->getTechnique(0)->getPass(0)->getTextureUnitState(0); texture->setTextureRotate( Degree( -rRotation ) );

In this part:

... if( rRotationToXAxis >= 0 ) { rRotation = rRotationToZAxis; } else { if( rRotationToZAxis >= 0 ) { rRotation = rRotationToZAxis - rRotationToXAxis * 2; } else { rRotation = rRotationToZAxis + rRotationToXAxis * 2; } } ...

I'm figuring out if the camera is looking along the Z-Axis (in positive direction) and if so I just use the rotation to the Z-Axis, but when the camera is looking the other way you will have to add or subtract the rotation from the X-Axis to be able to rotate 180 degrees. Whether to add or to subtract depends if you are looking in a positive direction along side the X-Axis or not.

When the camera is pointing in the negative direction of the Z-Axis, rRotationFromZAxis will still give you a value between 90 & -90. Now to compensate for that, you just multiply rRotationsFromXAxis by 2.

Original Author: Joost Passon, Release Date: January 5th, 2006