A method for visualizing flow data from computation fluid dynamics (CFD) applications in 2-dimensions (2D) includes receiving a 3-dimensional (3D) image volume from a CFD simulation of fluids flowing through vessels in a patient that is a snapshot of a fluid flow in the vessels at a certain time, subdividing the 3D image volume into 3D data blocks, minimizing a sum over a matrix of energy interactions defined for each pair of data blocks in the 3D image volume, where the minimization preserves a local shape of the vessels, where minimizing the sum over the matrix of energy interactions is performed on a graphics processing unit (GPU), and using the minimized energy interaction matrix to display on a monitor a 2D sketch of the 3D image volume, where the 2D sketch is displayed in real-time with respect to the time scale of the CFD simulation.