{"action":"created","issue":{"url":"https://api.github.com/repos/bempp/bempp/issues/287","repository_url":"https://api.github.com/repos/bempp/bempp","labels_url":"https://api.github.com/repos/bempp/bempp/issues/287/labels{/name}","comments_url":"https://api.github.com/repos/bempp/bempp/issues/287/comments","events_url":"https://api.github.com/repos/bempp/bempp/issues/287/events","html_url":"https://github.com/bempp/bempp/issues/287","id":186743904,"number":287,"title":"derivative of Laplace3dSingleLayerPotentialOperator","user":{"login":"SvenFanghaenel","id":3638980,"avatar_url":"https://avatars.githubusercontent.com/u/3638980?v=3","gravatar_id":"","url":"https://api.github.com/users/SvenFanghaenel","html_url":"https://github.com/SvenFanghaenel","followers_url":"https://api.github.com/users/SvenFanghaenel/followers","following_url":"https://api.github.com/users/SvenFanghaenel/following{/other_user}","gists_url":"https://api.github.com/users/SvenFanghaenel/gists{/gist_id}","starred_url":"https://api.github.com/users/SvenFanghaenel/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/SvenFanghaenel/subscriptions","organizations_url":"https://api.github.com/users/SvenFanghaenel/orgs","repos_url":"https://api.github.com/users/SvenFanghaenel/repos","events_url":"https://api.github.com/users/SvenFanghaenel/events{/privacy}","received_events_url":"https://api.github.com/users/SvenFanghaenel/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":3,"created_at":"2016-11-02T08:58:27Z","updated_at":"2016-11-04T00:05:14Z","closed_at":null,"body":"Hello, \r\ni want to calculate the electric field from a assembly of charged electrodes.\r\n If i have calculated the neumann trace at the boundary, is there an operator to calculate directly the electric field for the laplace problem with dirichlet boundaryconditions from this point. (I know it would be possible to calculate the electric potential and than to calculate numerically the derivative in each direction to get the electric field, but this is very awkward).\r\nOr is it possible to create  a own operator (just the derivative of the Laplace3dSingleLayerPotentialOperator at the evaluation point in x,y,z direction).\r\nI am using the BEMPP 2.0 Version.\r\nThanx Sven from Germany"},"comment":{"url":"https://api.github.com/repos/bempp/bempp/issues/comments/258310686","html_url":"https://github.com/bempp/bempp/issues/287#issuecomment-258310686","issue_url":"https://api.github.com/repos/bempp/bempp/issues/287","id":258310686,"user":{"login":"wsmigaj","id":1110609,"avatar_url":"https://avatars.githubusercontent.com/u/1110609?v=3","gravatar_id":"","url":"https://api.github.com/users/wsmigaj","html_url":"https://github.com/wsmigaj","followers_url":"https://api.github.com/users/wsmigaj/followers","following_url":"https://api.github.com/users/wsmigaj/following{/other_user}","gists_url":"https://api.github.com/users/wsmigaj/gists{/gist_id}","starred_url":"https://api.github.com/users/wsmigaj/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/wsmigaj/subscriptions","organizations_url":"https://api.github.com/users/wsmigaj/orgs","repos_url":"https://api.github.com/users/wsmigaj/repos","events_url":"https://api.github.com/users/wsmigaj/events{/privacy}","received_events_url":"https://api.github.com/users/wsmigaj/received_events","type":"User","site_admin":false},"created_at":"2016-11-04T00:05:13Z","updated_at":"2016-11-04T00:05:13Z","body":"Hi Sven,\r\n\r\nOK, if you were using the C++ interface, I would say this whole procedure is straightforward, but creation of the Python wrappers is a bit complicated. There used to be a tutorial on adding custom operators to BEM++ on the library's website, but I think it was removed after BEM++ 3.0 was released. So I wrote the code for you :-). You can download it from the https://github.com/wsmigaj/laplace-potential-gradient repository. After cloning the repository you'll need to create a ``build`` subdirectory, and then run ``cmake ..`` and ``make install`` in it. (The installation phase will copy some files to the BEM++ installation directory.) \r\n\r\nThe repository contains a small library that implements a custom potential operator defined as the gradient of the single-layer potential operator for the Laplace equation in 3D. The ``test_gradient.py`` script demonstrates how to use it (it prints the _y_ derivative of the potential calculated using the new operator at a series of points, juxtaposed with the same derivative calculated by finite differences).\r\n\r\nLet me know if it helps or if you have problems with building, installation or usage of this code. I hope after looking at it you'll be able to implement a similar custom operator calculating the gradient of the double-layer potential operator. \r\n\r\nBest regards,\r\nWojciech"}}
{"actor":{"display_login":"wsmigaj"}}