Many papers and software have different algorithm methods of reducing modelling size (either its vertices, faces, edges and triangle counts). A prominent figure who did a lot of work in this area is Michael Garland who explored many techniques to optimise and simplify 3D models. The interest of the architecture school is to find the best reduction / simplification software that best suits different CAD models from all the techniques created. Geoffrey Bawa’s Singapore Botanical Garden Cloud Forest Biosphere 3D terrain model is used for this exercise with the canal project, Mario Botta’s The Cymbalista Synagogue and Jewish Heritage Center and Mies Van der Rohe Farnsworth’s House. All the models used are in 3DS and DXF file format. The Cloud Forest Biosphere is an unbuilt project which was constructed as part of this research. The canal project and Farnsworth’s House are 3D models constructed by fellow students in their design and independent study module. The Cymbalista Synagogue and Jewish Heritage Centre 3D model was constructed for an independent study module.
Software chosen to perform the experiments are:
(i) Okino Polytrans / Nugraf (Michael Garland’s Quadric Error Metrics Algorithm) as shown in Figure 3.13.
This technique uses what Garland calls quadric error metrics (QEM) and vertex pair contraction, which has been restricted to edge contraction in this application (Garland and Heckbert 1997 & 1998). Edge contraction simply means that the two end vertices of a
model edge are replaced by a single new vertex as shown in Figure 3.12. This target vertex is usually somewhere in between the other two, in a place where it best
approximates the original model. This edge contraction step removes a vertex and one, two, or more faces from the model, depending on the mesh neighbourhood.
Figure 3.12. Garland’s Iterative Edge Contraction Source: http://graphics.cs.uiuc.edu~/garland/home.html
Figure 3.13. Okino Polytrans (90% Reduction) Cloud Forest Biosphere and Jewish Synagogue
(ii) Autodesk® 3ds Max® (Multiresolution Mesh Decimation Algorithm) as shown in Figure 3.13.
Figure 3.14. 3ds Max® Cloud Forest Biosphere (90% reduction) (only mesh models can be reduced so only this model can be tested)
(iii) Right Hemisphere Deep Exploration (EONTM CAD – triangles reduction algorithm) as shown in Figure 3.15.
Figure 3.15. Right Hemisphere Deep Exploration (90% & 80% Reduction) Cloud Forest Biosphere and Jewish Synagogue
(iv) Raindrop Geomagic (3D Scanner editing software –triangles reduction based upon the deviation of new vertices to the original polygonal model surface) as shown in Figure 3.16.
Figure 3.16. Raindrop Geomagic (90% reduction) and Cloud Forest Biosphere & Jewish Synagogue
All four software simplification and reduction from 100% to the range of 10% - 40% are shown in Figure 3.17.
Figure 3.17. All the CAD files Simplification / Reduction from 100% to 10% - 40%
(UpperLeft: Polytrans UpperRight: Geomagic LowerRight: 3ds Max®
LowerLeft:EONTM CAD)
There are many other algorithm methods in the market which are either developed individually by computer science students and lecturers or commercially released.
(i) Action3D Inc. Action3D (Only supports X and 3DS file formats) (ii) Trapezium Chisel
(iii) Antonio Cortés Carrillo Progressive Fans
(iv) Erik Pojar’s Progressive Meshes (Maya® plug-in) (v) Paralelo Computaỗóo’s ProgMesh
(vi) System In Motion Rational Reducer (3ds Max® plug-in) (vii) Realax RXpolyred
(viii) Sergei Zawelsky VIZup (only supports VRML WRL file format)
The next step is to export all the 3D models into EONTM CAD and EONTM StudioTM ProfessionalTM. The entire list of them are shown in Figure 3.18.
Figure 3.18. All the output EONTM StudioTM ProfessionalTM files from above.
(UpperLeft: UpperRight: LowerRight: LowerLeft)
From the comparisons done, a few conclusions are obvious:
(i) Parameters to control reduction are useful (boundary reduction, average vertices reduction, vertex clustering (average of two vertices), vertices stitching), and the more the better.
(ii) There is limited reduction as the percentage goes beyond 70% and above;
some algorithms will prevent further reductions.
(iii) Each software has its strength and weakness on reduction depending on
different modelling types (landscape, organic to linear models).
(iv) Smaller files may be too ugly to show at all, sometimes the reduction will make some surfaces totally disappear.
(v) 3ds Max®’s Multires modifier only works for mesh models, not spline / patch or NURBS.
(vi) EONTM CAD seems most efficient without tweaking any parameters for all four software probably because it is the best medium of preparation before going into EONTM StudioTM Professional
Therefore, this method is only for very complicated terrains / organic objects because the loss of vertices will not be very visible to the naked eye. If for any reason, there are many details to be drawn in linear modelling, polygon reductions / simplifications have to be done layer by layer to maintain its form so that it will not be too distorted or have the ‘after destruction/explosion’ feeling.