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RotatingATextureUsingGetYaw         Rotating a texture using the getYaw() function
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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.

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// 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:

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...
   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

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