1. A method, comprising: generating a three-dimensional (3D) sketch comprising a plurality of three-dimensional (3D) curves according to two-dimensional (2D) input, wherein said generating comprises iteratively performing: obtaining input indicating a 2D stroke; analyzing the 2D stroke according to 3D curve information projected into 2D to determine if the 2D stroke input can be applied to one or more 3D curves; if the 2D stroke can be applied to one or more 3D curves, applying the 2D stroke to the one or more 3D curves; and if the 2D stroke cannot be applied to one or more 3D curves, generating a new 3D curve from the 2D stroke input.