code: function getEyeMatrices( frameData ) {
  
  		// Compute the matrix for the position of the head based on the pose
  		if ( frameData.pose.orientation ) {
  
  			poseOrientation.fromArray( frameData.pose.orientation );
  			headMatrix.makeRotationFromQuaternion( poseOrientation );
  
  		}	else {
  
  			headMatrix.identity();
  
  		}
  
  		if ( frameData.pose.position ) {
  
  			posePosition.fromArray( frameData.pose.position );
  			headMatrix.setPosition( posePosition );
  
  		}
  
  		// The view matrix transforms vertices from sitting space to eye space. As such, the view matrix can be thought of as a product of two matrices:
  		// headToEyeMatrix * sittingToHeadMatrix
  
  		// The headMatrix that we've calculated above is the model matrix of the head in sitting space, which is the inverse of sittingToHeadMatrix.
  		// So when we multiply the view matrix with headMatrix, we're left with headToEyeMatrix:
  		// viewMatrix * headMatrix = headToEyeMatrix * sittingToHeadMatrix * headMatrix = headToEyeMatrix
  
  		eyeMatrixL.fromArray( frameData.leftViewMatrix );
  		eyeMatrixL.multiply( headMatrix );
  		eyeMatrixR.fromArray( frameData.rightViewMatrix );
  		eyeMatrixR.multiply( headMatrix );
  
  		// The eye's model matrix in head space is the inverse of headToEyeMatrix we calculated above.
  
  		eyeMatrixL.getInverse( eyeMatrixL );
  		eyeMatrixR.getInverse( eyeMatrixR );
  
  	}
docs: Compute model matrices of the eyes with respect to the head.