SecondSkin is an interactive 3D sketched-based modeling system, that facilitates single-view sketching but also allows the user to manipulate the camera freely. The interface is designed to be used with a graphics tablet. We implemented our system on a PC with an i7 Intel CPU, 8 GB of RAM, and an ATI Radeon HD 5700. The system runs completely in real-time with a barely noticeable pause when interactively constructing mesh surfaces and volumes. The system uses a kd-tree for 3D distance calculations used to to determine height values between newly sketched strokes and the base layer. Distance offset surfaces are approximated on the GPU using a vertex shader to inflate the mesh. We find this method reasonable, since these surfaces are only used for stroke projection from the current view.