addAttribute Add an attribute to the object.
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  INPUT
  1 [attribute]
    Name of attribute which should be added. Actually, possible choices are:
      * 'slope'
         Slope (from 0 to 100 gradian) of each point based on its normal vector.
         This attribute requires the components of the normal vectors nx, ny,
         and nz for each point. They can be calculated with the method 'normals'
         (see 'help pointCloud.normals').
      * 'exposition'
         Exposition (from 0 to 400 gradian) of each point based on its normal
         vector. This attribute requires the components of the normal vectors
         nx, ny, and nz for each point. They can be calculated with the method
         'normals' (see 'help pointCloud.normals').
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  EXAMPLES
  1 Calculate and visualize the slope attribute of a point cloud.
    pc = pointCloud('Lion.xyz', 'Attributes', {'nx' 'ny' 'nz' 'roughness'});
    pc.addAttribute('slope');
    pc.plot('Color', 'A.slope', 'MarkerSize', 5);
 
  2 Calculate and visualize the exposition attribute of a point cloud.
    pc = pointCloud('Lion.xyz', 'Attributes', {'nx' 'ny' 'nz' 'roughness'});
    pc.addAttribute('exposition');
    pc.plot('Color', 'A.exposition', 'MarkerSize', 5);
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  philipp.glira@gmail.com
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