## Group Yoshiyasu

Group Description |
Image editting and mesh deformation problem from Y. Yoshiyasu, Keio Univ., Japan I uploaded 5 matrices A1,b1,A2,b2 and D (for x=(A1'*A1)/(A1'*b1) and v=(A2'*D*A2)/(A2'*D*b2)). What I'm doing is template-mesh deformation to match with silhouettes. In this process, there are two kinds of linear systems that I have to solve. First one is smooth vector field construction from images, which is harmonic interpolation (minimizing laplacian: Lx=0) of intensity gradient field p. I'm solving this by normal equation and cholesky factorization. x=(A1'*A1)/(A1'*b1) where A1=[L;C] and b1=[zeros(size(length(L),1);1);C*p]. C is a square diagonal matrix containing weights. I'm doing this on a 400x300 image, so Ix=reshape(x,400,300) must be done to get the vector field. After solving y direction for Iy, the result is visualized with quiver(Ix,Iy). At each iteration the both C submatrix and the right-hand-side change but L remains unchanged. Second one is template deformation using above vector field. I'm solving this by: v=(A2'*D*A2)/(A2'*D*b2) where D is diagonal matrix containing weights. Structures of A2 and b2 are a little bit more complex than A1 and b1, but they are similar. Both systems are not quite time-consuming for themselves, but I iterate this process more than 10 times for 10 views. So I would like them to be faster and also I'd like to reuse and update the factored matrix (if it's possible). [Reply: if all of C changes at each step, this is a nearly n-rank change, so an update/downdate process would be much more expensive than refactorizing the matrix. Update/downdate is effective for low-rank changes. In the collection,] |
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**all 2**collection matricesId | Name | Group | Rows | Cols | Nonzeros | Kind | Date | Download File |
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2248 | image_interp | Yoshiyasu | 240,000 | 120,000 | 711,683 | Computer Graphics/Vision Problem | 2009 | MATLAB Rutherford Boeing Matrix Market |

2249 | mesh_deform | Yoshiyasu | 234,023 | 9,393 | 853,829 | Computer Graphics/Vision Problem | 2009 | MATLAB Rutherford Boeing Matrix Market |