Study On Paper-based 3D Printing Based On DEM Data

One of the important roles of digital elevation model(DEM) is to stereoscopic display the three-dimensional topographic map with computer technology. However, the simulated image in the practical application cannot convey exactly three-dimensional information to people, although the virtual reality technology has been developing quickly in recent years. But the mould manufacturing of three-dimensional terrain model faces bottleneck problem, i.e. high difficulty, high cost, and short service life. Three-dimensional printing technology provides a solution for three-dimensional topographic map manufacturing. Based on NSDTF-DEM data, modeling, texture mapping and paper-based three-dimensional printing were made in this thesis to explore the three-dimensional printing technology of three-dimensional topographic map.A tetrahedral mesh generation algorithm based on Crust algorithm was proposed, which introduced region division and Delaunay tetrahedral mesh generation into the Crust algorithm to achieve the surface reconstruction of DEM point cloud. With some improving in efficiency, the adhesion problem on the edge of nonclosed point cloud had been solved, and the deformed triangulated surfaces had been avoided as well with the new algorithm, which well realized the construction of three-dimensional topographic Map.A texture mapping method was proposed based on the “depth map” of three-dimensional model, the depth map could be obtained by vertical projection of three-dimensional model, and the texture image whose size was the same as the depth image was generated through color assignment according to the relationship between the gray value of the depth map and the number of column in the index image designed in Photoshop. Taking the sampling characteristics of DEM data into account, the new algorithm avoided the image scaling operation and assigned the color value directly to the vertices of the three-dimensional model, which not only got high color accuracy, but also achieve rich color level.Two experiments were taken aiming at the color and print time of paper-based three-dimensional printing. The results showed that, coating a layer of aqueous adhesives on the surface of three-dimensional model after three-dimensional printing could further promote the ink penetration and expansion, so that the paper-based three-dimensional model could get more consistent, real and natural color; the cutting-bonding frame proposed in this paper could be used to three-dimensional output the model whose size was beyond the maximum size of the printer. Finally the color three-dimensional topographic map of DEM was output by the paper-based three-dimensional printing technology.