I will consider the sum of planar diagrams for open strings ending on D-branes. The result is that the sum of planar diagrams can be rewritten in terms of the propagation of a closed string in a modified background. For superstrings ending on D3-branes we obtain the full D3-brane supergravity background including the AdS5xS5 near horizon region. As side results we find a closed form for the scattering of arbitrary closed string states from a D3 brane and the (supersymmetric) Hamiltonian of a closed string in the D3-brane background, including all fermionic terms. Based on: arXiv:hep-th/0703218 and arXiv:hep-th/0603202