The CityGML objects generated can easily be transformed into the STL (Standard Triangle/Tesselation Language) format, which can be used for 3D printing. The 3D print is executed using a 3D printer called 'Form 2' owned by the Chair of Computational Modeling and Simulation (TUM).
Approach
The software used to create a 3D printed version of the 'Flatiron Building' together with short descriptions how they were used, is summarized in the following table.
| Software | Task | Description |
|---|---|---|
FME | Select CityGML objects and transform to STL | First the famous 'Flatiron Building', along with all CityGML street space objects directly connected to the building, are selected using the software FME. Additionally a base is created by downward extruding a bounding box of the model.These objects are then aggregated and output as '.stl' file. |
123Design | Create 3D text | The STL-Model is imported into the software '123Design'. This software is used to create 3D text such as the name of the building or adjacent street names. The '3D text objects' are then placed on the model. This new model is again exported as '.stl' file. |
3D Builder | Create a hollow model | In order to use as few material as possible, the model is hollowed out using the software 3D Builder. This is achieved by scaling down the model and then substracing it from the original. |
| PreForm | Prepare 3D print | Before the 3D print can be started the software PreForm is used to put the model into the right position and also to calculated supporting structures that can be removed after the printing process. |
Form 2 Desktop SLA 3D Printer
3D Printing Process
The 3D printer creates a model using the so called stereolithography technology by producting parts in a layer by layer fashion. A laser selectively illuminates the transparent bottom of a tank filled with a liquid photo-polymerizing resin. The solidified resin is progressively dragged up by a lifting platform. After the printing process the supporting structures can be removed. In this case the model was made of 2557 layers resulting in a printing time of 17 hours.
Result
The result of this 3D print is an approximately 9 cm high model of the Flatiron Building (1 Euro coin for comparison). In reality this building has a height of 91 meters, which means the model was generated at a scale of 1:1000.
