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(PDM & SDM)
 
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          SDM
(Squared Distance Minimization) was originally proposed by Pottmann et al [Pottmann et al. 2003]. It is an iterative optimization scheme for approximating a target shape with a piecewise smooth curve or surface, such as a B-spline curve or surface, or a subdivision surface. SDM has superior performance in both convergence and stability over PDM (Point Distance Minimization) and TDM (Tangent Distance Minimization).
 

   
 

PDM uses the PD error term, which measures the squared distance between the data point X k and a particular point P ( t k ) on the fitting curve, i.e.
 

TDM uses the TD error term, which measures the squared distance from X k to the tangent of the fitting curve at P ( t k ), i.e.
 

SDM uses the SD error term, which is the local quadratic approximant of the squared distance from the sample point P k to the target curve C , i.e.