111 lines
3.2 KiB
C
111 lines
3.2 KiB
C
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/*
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Bullet Continuous Collision Detection and Physics Library
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Copyright (c) 2003-2013 Erwin Coumans http://bulletphysics.org
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This software is provided 'as-is', without any express or implied warranty.
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In no event will the authors be held liable for any damages arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it freely,
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subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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///original version written by Erwin Coumans, October 2013
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#ifndef BT_SOLVE_PROJECTED_GAUSS_SEIDEL_H
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#define BT_SOLVE_PROJECTED_GAUSS_SEIDEL_H
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#include "btMLCPSolverInterface.h"
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///This solver is mainly for debug/learning purposes: it is functionally equivalent to the btSequentialImpulseConstraintSolver solver, but much slower (it builds the full LCP matrix)
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class btSolveProjectedGaussSeidel : public btMLCPSolverInterface
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{
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public:
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btScalar m_leastSquaresResidualThreshold;
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btScalar m_leastSquaresResidual;
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btSolveProjectedGaussSeidel()
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:m_leastSquaresResidualThreshold(0),
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m_leastSquaresResidual(0)
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{
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}
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virtual bool solveMLCP(const btMatrixXu & A, const btVectorXu & b, btVectorXu& x, const btVectorXu & lo,const btVectorXu & hi,const btAlignedObjectArray<int>& limitDependency, int numIterations, bool useSparsity = true)
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{
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if (!A.rows())
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return true;
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//the A matrix is sparse, so compute the non-zero elements
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A.rowComputeNonZeroElements();
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//A is a m-n matrix, m rows, n columns
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btAssert(A.rows() == b.rows());
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int i, j, numRows = A.rows();
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btScalar delta;
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for (int k = 0; k <numIterations; k++)
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{
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m_leastSquaresResidual = 0.f;
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for (i = 0; i <numRows; i++)
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{
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delta = 0.0f;
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if (useSparsity)
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{
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for (int h=0;h<A.m_rowNonZeroElements1[i].size();h++)
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{
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int j = A.m_rowNonZeroElements1[i][h];
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if (j != i)//skip main diagonal
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{
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delta += A(i,j) * x[j];
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}
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}
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} else
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{
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for (j = 0; j <i; j++)
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delta += A(i,j) * x[j];
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for (j = i+1; j<numRows; j++)
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delta += A(i,j) * x[j];
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}
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btScalar aDiag = A(i,i);
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btScalar xOld = x[i];
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x [i] = (b [i] - delta) / aDiag;
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btScalar s = 1.f;
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if (limitDependency[i]>=0)
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{
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s = x[limitDependency[i]];
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if (s<0)
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s=1;
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}
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if (x[i]<lo[i]*s)
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x[i]=lo[i]*s;
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if (x[i]>hi[i]*s)
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x[i]=hi[i]*s;
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btScalar diff = x[i] - xOld;
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m_leastSquaresResidual += diff*diff;
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}
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btScalar eps = m_leastSquaresResidualThreshold;
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if ((m_leastSquaresResidual < eps) || (k >=(numIterations-1)))
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{
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#ifdef VERBOSE_PRINTF_RESIDUAL
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printf("totalLenSqr = %f at iteration #%d\n", m_leastSquaresResidual,k);
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#endif
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break;
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}
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}
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return true;
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}
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};
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#endif //BT_SOLVE_PROJECTED_GAUSS_SEIDEL_H
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