245 lines
8.9 KiB
C
245 lines
8.9 KiB
C
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// This file is part of libigl, a simple c++ geometry processing library.
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//
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// Copyright (C) 2013 Alec Jacobson <alecjacobson@gmail.com>
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//
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// This Source Code Form is subject to the terms of the Mozilla Public License
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// v. 2.0. If a copy of the MPL was not distributed with this file, You can
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// obtain one at http://mozilla.org/MPL/2.0/.
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#ifndef IGL_ARAP_ENERGY_TYPE_DOF_H
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#define IGL_ARAP_ENERGY_TYPE_DOF_H
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#include "igl_inline.h"
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#include <Eigen/Dense>
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#include <Eigen/Sparse>
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#include "ARAPEnergyType.h"
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#include <vector>
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namespace igl
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{
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// Caller example:
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//
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// Once:
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// arap_dof_precomputation(...)
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//
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// Each frame:
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// while(not satisfied)
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// arap_dof_update(...)
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// end
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template <typename LbsMatrixType, typename SSCALAR>
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struct ArapDOFData;
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///////////////////////////////////////////////////////////////////////////
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//
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// Arap DOF precomputation consists of two parts the computation. The first is
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// that which depends solely on the mesh (V,F), the linear blend skinning
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// weights (M) and the groups G. Then there's the part that depends on the
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// previous precomputation and the list of free and fixed vertices.
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//
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///////////////////////////////////////////////////////////////////////////
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// The code and variables differ from the description in Section 3 of "Fast
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// Automatic Skinning Transformations" by [Jacobson et al. 2012]
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//
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// Here is a useful conversion table:
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//
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// [article] [code]
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// S = \tilde{K} T S = CSM * Lsep
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// S --> R S --> R --shuffled--> Rxyz
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// Gamma_solve RT = Pi_1 \tilde{K} RT L_part1xyz = CSolveBlock1 * Rxyz
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// Pi_1 \tilde{K} CSolveBlock1
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// Peq = [T_full; P_pos]
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// T_full B_eq_fix <--- L0
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// P_pos B_eq
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// Pi_2 * P_eq = Lpart2and3 = Lpart2 + Lpart3
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// Pi_2_left T_full + Lpart3 = M_fullsolve(right) * B_eq_fix
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// Pi_2_right P_pos Lpart2 = M_fullsolve(left) * B_eq
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// T = [Pi_1 Pi_2] [\tilde{K}TRT P_eq] L = Lpart1 + Lpart2and3
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//
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// Precomputes the system we are going to optimize. This consists of building
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// constructor matrices (to compute covariance matrices from transformations
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// and to build the poisson solve right hand side from rotation matrix entries)
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// and also prefactoring the poisson system.
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//
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// Inputs:
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// V #V by dim list of vertex positions
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// F #F by {3|4} list of face indices
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// M #V * dim by #handles * dim * (dim+1) matrix such that
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// new_V(:) = LBS(V,W,A) = reshape(M * A,size(V)), where A is a column
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// vectors formed by the entries in each handle's dim by dim+1
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// transformation matrix. Specifcally, A =
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// reshape(permute(Astack,[3 1 2]),n*dim*(dim+1),1)
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// or A = [Lxx;Lyx;Lxy;Lyy;tx;ty], and likewise for other dim
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// if Astack(:,:,i) is the dim by (dim+1) transformation at handle i
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// handles are ordered according to P then BE (point handles before bone
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// handles)
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// G #V list of group indices (1 to k) for each vertex, such that vertex i
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// is assigned to group G(i)
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// Outputs:
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// data structure containing all necessary precomputation for calling
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// arap_dof_update
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// Returns true on success, false on error
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//
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// See also: lbs_matrix_column
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template <typename LbsMatrixType, typename SSCALAR>
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IGL_INLINE bool arap_dof_precomputation(
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const Eigen::MatrixXd & V,
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const Eigen::MatrixXi & F,
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const LbsMatrixType & M,
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const Eigen::Matrix<int,Eigen::Dynamic,1> & G,
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ArapDOFData<LbsMatrixType, SSCALAR> & data);
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// Should always be called after arap_dof_precomputation, but may be called in
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// between successive calls to arap_dof_update, recomputes precomputation
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// given that there are only changes in free and fixed
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//
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// Inputs:
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// fixed_dim list of transformation element indices for fixed (or partailly
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// fixed) handles: not necessarily the complement of 'free'
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// NOTE: the constraints for fixed transformations still need to be
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// present in A_eq
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// A_eq dim*#constraint_points by m*dim*(dim+1) matrix of linear equality
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// constraint coefficients. Each row corresponds to a linear constraint,
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// so that A_eq * L = Beq says that the linear transformation entries in
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// the column L should produce the user supplied positional constraints
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// for each handle in Beq. The row A_eq(i*dim+d) corresponds to the
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// constrain on coordinate d of position i
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// Outputs:
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// data structure containing all necessary precomputation for calling
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// arap_dof_update
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// Returns true on success, false on error
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//
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// See also: lbs_matrix_column
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template <typename LbsMatrixType, typename SSCALAR>
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IGL_INLINE bool arap_dof_recomputation(
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const Eigen::Matrix<int,Eigen::Dynamic,1> & fixed_dim,
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const Eigen::SparseMatrix<double> & A_eq,
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ArapDOFData<LbsMatrixType, SSCALAR> & data);
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// Optimizes the transformations attached to each weight function based on
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// precomputed system.
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//
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// Inputs:
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// data precomputation data struct output from arap_dof_precomputation
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// Beq dim*#constraint_points constraint values.
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// L0 #handles * dim * dim+1 list of initial guess transformation entries,
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// also holds fixed transformation entries for fixed handles
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// max_iters maximum number of iterations
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// tol stopping criteria parameter. If variables (linear transformation
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// matrix entries) change by less than 'tol' the optimization terminates,
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// 0.75 (weak tolerance)
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// 0.0 (extreme tolerance)
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// Outputs:
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// L #handles * dim * dim+1 list of final optimized transformation entries,
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// allowed to be the same as L
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template <typename LbsMatrixType, typename SSCALAR>
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IGL_INLINE bool arap_dof_update(
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const ArapDOFData<LbsMatrixType,SSCALAR> & data,
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const Eigen::Matrix<double,Eigen::Dynamic,1> & B_eq,
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const Eigen::MatrixXd & L0,
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const int max_iters,
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const double tol,
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Eigen::MatrixXd & L
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);
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// Structure that contains fields for all precomputed data or data that needs
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// to be remembered at update
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template <typename LbsMatrixType, typename SSCALAR>
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struct ArapDOFData
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{
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typedef Eigen::Matrix<SSCALAR, Eigen::Dynamic, Eigen::Dynamic> MatrixXS;
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// Type of arap energy we're solving
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igl::ARAPEnergyType energy;
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//// LU decomposition precomptation data; note: not used by araf_dop_update
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//// any more, replaced by M_FullSolve
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//igl::min_quad_with_fixed_data<double> lu_data;
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// List of indices of fixed transformation entries
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Eigen::Matrix<int,Eigen::Dynamic,1> fixed_dim;
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// List of precomputed covariance scatter matrices multiplied by lbs
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// matrices
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//std::vector<Eigen::SparseMatrix<double> > CSM_M;
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std::vector<Eigen::MatrixXd> CSM_M;
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LbsMatrixType M_KG;
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// Number of mesh vertices
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int n;
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// Number of weight functions
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int m;
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// Number of dimensions
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int dim;
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// Effective dimensions
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int effective_dim;
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// List of indices into C of positional constraints
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Eigen::Matrix<int,Eigen::Dynamic,1> interpolated;
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std::vector<bool> free_mask;
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// Full quadratic coefficients matrix before lagrangian (should be dense)
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LbsMatrixType Q;
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//// Solve matrix for the global step
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//Eigen::MatrixXd M_Solve; // TODO: remove from here
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// Full solve matrix that contains also conversion from rotations to the right hand side,
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// i.e., solves Poisson transformations just from rotations and positional constraints
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MatrixXS M_FullSolve;
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// Precomputed condensed matrices (3x3 commutators folded to 1x1):
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MatrixXS CSM;
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MatrixXS CSolveBlock1;
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// Print timings at each update
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bool print_timings;
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// Dynamics
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bool with_dynamics;
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// I'm hiding the extra dynamics stuff in this struct, which sort of defeats
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// the purpose of this function-based coding style...
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// Time step
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double h;
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// L0 #handles * dim * dim+1 list of transformation entries from
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// previous solve
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MatrixXS L0;
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//// Lm1 #handles * dim * dim+1 list of transformation entries from
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//// previous-previous solve
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//MatrixXS Lm1;
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// "Velocity"
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MatrixXS Lvel0;
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// #V by dim matrix of external forces
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// fext
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MatrixXS fext;
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// Mass_tilde: MT * Mass * M
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LbsMatrixType Mass_tilde;
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// Force due to gravity (premultiplier)
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Eigen::MatrixXd fgrav;
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// Direction of gravity
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Eigen::Vector3d grav_dir;
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// Magnitude of gravity
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double grav_mag;
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// Π1 from the paper
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MatrixXS Pi_1;
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// Default values
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ArapDOFData():
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energy(igl::ARAP_ENERGY_TYPE_SPOKES),
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with_dynamics(false),
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h(1),
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grav_dir(0,-1,0),
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grav_mag(0)
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{
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}
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};
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}
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#ifndef IGL_STATIC_LIBRARY
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# include "arap_dof.cpp"
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#endif
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#endif
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