SpectacularAI / HybVIO

What do these two following lines mean?

Lines 337 to 338 in e325353

    
           const Vector3d dX_Eerror = -X.solve(dETE.block<3, 3>(0, j * 3) * X.solve(Eerror)); 
        
           dpfi.col(j) += -X.solve(dEerror.col(j)) - dX_Eerror;

Thanks!

Hi @fushi219. We unfortuntately cannot spend more time explaining the code line by line (ref #23 , #24). The overall purpose of the method is explained in the PIVO paper and the there is a unit test to verify that the formulas for the derivatives are correct. Each step follows from, e.g., chain rule of differentation or other generic (linear-algebraic) differentiation formulas

	const Vector3d dX_Eerror = -X.solve(dETE.block<3, 3>(0, j * 3) * X.solve(Eerror));
	dpfi.col(j) += -X.solve(dEerror.col(j)) - dX_Eerror;

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