Billboarded Cutaway Visualization for Subsurface Urban Sewer Networks

Visualizing the results of a flood simulation interactively in real-time has become very important due to the increasing number of flood hazards in the recent past. An important part of a flood simulation is the impact on the sewer system of the flooded city. For the simulation itself only a very primitive data structure of a sewer system is required. Therefore this thesis proposes an innovative and efficient technique to render sewage pipes and to visualize the water flow inside of them. With a simple underlying data structure of node positions, billboarded sewage pipes are constructed in the geometry shader. With a proxy geometry the stencil buffer is utilized to distinguish outside and inside of the pipe and the billboards are drawn accordingly. In addition another technique is introduced to cut-open the occluding terrain to expose the sewage pipes to the viewer. Therefore a two dimensional distance transform of the sewer network is generated. The created distance field is used to discard fragments of the terrain, which are relatively close to a pipe. Further an artificial thickness is added to the cut-open terrain analytically in image-space. The techniques are presented in detail and their implementation is demonstrated in Unity3D. It is evaluated by comparing the result to multiple conventions for computer generated cutaways. Additionally the feedback from visualization experts and the technical performance is presented. The results show that billboarded and cut-open tubular geometry can be rendered fast, efficient and with a low memory footprint. Furthermore the technique fulfills many of the design principles for cutaways and got positive feedback from visualization experts.