3D GIS MODELING APPLICATION FOR DEVELOPING THE BUTUAN CITY 3D MODEL Alexander T. Demetillo, Michelle V. Japitana and Peter John A. Galamiton CLAIMS-GIS Project, College of Engineering and Information Technology, Caraga State University, Butuan City, Philippines Email: atdemetillo@gmail.com Email: pjagalamiton@gmail.com Email: michelle.japitana@gmail.com KEY WORDS: 3D Modeling, CityEngine, LiDar ABSTRACT: This paper deals with the methods employed for the development of the 3D models of the establishments of Butuan City to be used further for real property assessment and flood simulation. The development of the 3D models was done by first extracting building footprints from the orthorectified satellite image of the study area. While a LiDAR data was used to calculate and manage the height of each buildings. A Digital Terrain Model (DTM) was also generated to be used as terrain and as a base layer of the 3D buildings. The digitized building footprints and the DTM were both an input data for the development of the 3D models within the ESRI CityEngine environment. Field surveys were then conducted to collect actual photographs of the buildings in the study area, which are vital in adding texture to the building model and a good reference on building structures. The processes on extruding, re-shaping, subdividing, adding textures, and forming the structures of the buildings were done manually with the aid of the conventional tools of the CityEngine. Outputs of this study show that a better representation of the city by employing 3D GIS modeling can be achieved. Further, the developed 3D city models are expected to enhance future endeavors on real property assessment and monitoring and in mitigating flood events in the City of Butuan, Philippines. 1. INTRODUCTION Since geographic information system (GIS) technologies have been successfully applied in urban planning and management, there have been increasing demands for three-dimensional (3D) realistic representations of GIS about the urban environment in spatial planning, design, and decision-making applications (Ranzinger and Gleixner, 1997, Pullar and Tidey, 2001). A CyberCity is a virtual representation of a city that enables a person to explore and interact, in cyberspace, with the vast amount of environmental and cultural information gathered about the city. The effective integrated data organization strategy for dynamical loading and progressive rendering, which enables CCGIS to support the development, design, and presentation of a large CyberCity, is stressed (Zhu, Li, Zhang, Hong, 2002). CyberCity is mainly applied for the outdoor scenes including natural and cultural objects such as DEM, rivers, roads, vegetation and building surfaces. In these applications, users can walkthrough, visit city landscape, and implement some operations such as querying, editing and analyzing in the outdoor 3D scenes except the indoor ones. Nevertheless, it is well known that in the real world, buildings, where people study, work or entertainment, etc., are the most important part in a city (Li, Zhu, Liu, Xu, 2004). Butuan City is the commercial and entertainment center of the Caraga region. It is categorized as a highly urbanized city since 1985 and as the regional center of the Caraga region since 1998. Located at the Northeastern part of Agusan Valley sprawling across the Agusan River is Butuan City, known for its colorful history and culture. By 2020, it is visioned that Butuan City will be a model for a sustainable forest-based economy in the country with the highest per capita and growth rate in Mindanao. Butuan City is now aiming to be a Smart City and Forest-based Economic City in the country like other highly urbanized cities in Asia (www.butuan.gov.ph). 3D City modelling is just one of the component toward establishing a smart city. It is the process of taking a shape and molding it into a completed 3D mesh. The most typical means of creating a 3D model is to take a simple object, called a primitive, and extend or "grow" it into a shape that can be refined and detailed. Primitives can be anything from a single point (called a vertex), a two-dimensional line (an edge), a curve (a spline), to three dimensional objects (faces or polygons). Box modeling is possibly the most popular technique, and bears a lot of resemblance to traditional sculpting. In box modeling, one starts with a primitive (usually a cube) and begins adding detail by "slicing" the cube into pieces and
extending faces of the cube to gradually create the form desired. People use box modeling to create the basic shape of the model. The downside of this is that the technique requires a lot of tweaking of the model along the way. Also, it is difficult to create a model that has a surface topology that lends well to animation. In this paper, the researcher uses the box modeling method in developing the 3D model buildings with the help of the 3D GIS Application software called CityEngine2012, an application produced by the ESRI Software Company. However, the researcher does not utilize some of the applications procedures and workflows instead; the researcher uses the tracing, cutting and simple push and pulls techniques. 2. MATERIALS AND METHODS The development of the 3D modeling was realized to visualize the current structural image of the Butuan City establishments thru the CityEngine2012 Software as main tool for developing 3D models. This development also uses ArcGIS10.1 to make and view the foot printed shape files of all the buildings of the subject area and use as input to the main software tool; and the ArcScene10.1 to view the output 3D model files. All the software used is produced by the ESRI Software Company. 2.1 Datasets Used This study used building footprint shapefiles of Butuan City in the downtown area, LiDar dataset for the elevations of the buildings, captured images of the actual buildings for the texture of the 3D models, SRTM DEM v4.1 with 90-meter resolution to be used as the base layer for the 3D models and Adobe Photoshop image enhancer software. Footprints are digitized from the orthorectified Quickbird image acquired by the City Government of Butuan and from any free satellite imagery (web maps: Google Earth, Google map and etc.) that shows better resolution. LiDar datasets used in this study was provided by the DREAM Program of the University of the Philippines Diliman. The SRTM DEM v4.1 data was downloaded from an open GIS resource site (http://www.philgis.org/freegisdata.htm) and the captured images were gathered using any digital camera. 2.2 3D Model Development Procedures The first step is to create a project folder for the 3D model within the CityEngine2012 Software, avoid using space or special characters in making a project folder name (for example, SAMPLE ). The project folder created was composed of the following sub-folders: assets, data, images, maps, models, rules, scenes and script folder, each folder were segregated the data used for the 3D development. The next step is to import all the datasets in the project folder by manually copying each datasets in each folder significantly with the datasets. Next is to create scene for the 3D development, simply right-click on the scenes folder and select new and then select CityEngine scene. After the creation of the scene, the main 3D development procedure will follow. Locate the footprint dataset in the data folder with the extension *.gdb (geodatabase file) and drag to the created scene. Each footprint corresponds to each establishment of the subject area.
Figure 1. The CityEngine working space showing the Butuan City footprint shapefiles. Next step is to build the body of the 3d models using the box modeling technique. Using the data gathered from the Lidar datasets (height and dimensions) extrude each footprint shape of the structures according to their height and elevation with the help of Polygon Shape Creation tool of the CityEngine2012 software. Figure 2. The Box modeling technique showing the extruded building footprint with respect to the height of the structures gathered from the Lidar dataset. Next step is to explore the usage of the Polygonal Shape Creation tool, this tool will be the main tool used in developing the 3D models. Polygonal Shape Creation tool is used to create lines, curves and faces of the 3D models, Rectangular Shape Creation is a type of Polygonal Shape Creation that is directly creates rectangular shapes in an open area or in the faces of the models. Push and pull are the technique using the extrusion of the faces of the models
Figure 3. The Polygonal Shape Creation tool showing the techniques in creating the face of the models. Continue the push and pull techniques until the desired models looks the same as the original one, in shape and structural form of the building. Figure 4. The comparison between the actual image of Saint Joseph Cathedral, Butuan City and 3D model with null texture. The next step is the image cleaning for the texture of the 3D models. Using the image enhancer software (Photoshop) start edit the image to be used as texture for the 3D models, erase all the disturbance and unwanted figures in the images shown in figure 5. Making sure that the dimension of the texture is the same as the dimension of the faces of the model. Save the images after enhancing and cleaning with appropriate extensions (*.png or *.jpg) into the image sub-folder in the project folder.
Figure 5. Using the Adobe Photoshop image stamp tool to enhance and clean the image for the texture of the model. The final step is the model texturing and model exporting. Using the enhanced and cleaned images in the image folder, drag the images to their desired model faces. Model faces with the same texture were need to be combined as one face before dragging the images to minimized the model file size in exporting. Exporting the 3D model to different 3d model file extensions is possible to the CityEngine2012, this can export to this extensions: Wavefront(*.obj), Autodesk (*.3ds), e-on Vue(*.vob), Autodesk (*.fbx), Collada(*.dae), RenderMan (*.rib), mental ray (*.mi), Massive (*.mas), Alembic(*.abc), Python Scripting(*.py), ESRI Shapefile(*.shp), ESRI FileGDB (*.gdb), Autodesk (*.dxf), Keyhole KML/KMZ (*.kml) and Images(*.png, jpg, etc.). Figure 6. The 3D model texturing, dragging the images to the model faces to create a model textures. Figure 7. The 3D models exported with extension (*.gdb), shown in ArcScene10.1 with the SRTM DEM v4.1 as base layer with corresponding road networks.
3. RESULTS AND DISCUSSION Figure 8 shows the resulting 3D models for the city proper of Butuan using a simple technique called the box modeling accompanied with another simple techniques that cuts through the natural process in the development of 3D models in CityEngine2012. In this study, some of the 3D development processing tools of the CityEngine2012 was not employed and sought for a solution to make the output files same as the output files of the natural process and lesser the file size of each output models. Figure 8. The 3D models of Saint Joseph Cathedral and UCPB, Butuan City, Philippines viewed from CityEngine2012. All 3D models has undergone quality checking in the ArcScene10.1 viewer to check the texture of all the output 3D models of CityEngine2012 for errors and missing images as shown in figure 9. All checked 3D models have been saved into another folder for finalization and compilation of all output files. Figure 9. The 3D models of Saint Joseph Cathedral and UCPB, Butuan City, Philippines viewed from ArcScene10.1 for texture checking.
4. CONCLUSION In this paper, we have presented a simplified technique in approach of developing 3D models of Butuan City using the 3D GIS application software. The 3D development procedure consisted of simplified steps in making the 3D models to fasten and minimized the file sized of the output models compared with the natural process in CityEngine2012 software which consisted of some complicated tools like coding, ruling, and other tools that can be easily by pass using other simplest techniques. ACKNOWLEDGEMENTS This research is one of the outputs of the Comprehensive Land Information Management System using Geographic Information System project. We are grateful to the Local Government of Butuan City for the financial support and to the Caraga State University for its trust. REFERENCES Zhu Q, Li D R, Zhang Y T, Hong D, 2002, Cyber City GIS (CCGIS): Integration of DEMs, Images, and 3D Models, Photogrammetric Engineering & Remote Sensing, Volume 68, Number 4, pp. 361-367 Ranzinger, M., and G. Gleixner, 1997. GIs Datasets for 3D Urban Planning, Computers, Environment and Urban Systems, 21(2): 159-173. Pullar, D.V., and M.E. Tidey, 2001, Coupling 3D Visualisation to Qualitative Assessment of Built Environment Designs, Landscape and Urban Planning, 55:29-40. Deren Li Qing Zhu Qiang Liu Peng Xu, 2004 From 2D to 3D GIS for CYBERCITY, State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, No129 Luo Yu Road, Wuhan, China, 430079, pp.1-8 About Butuan, Butuan City Official Site, http://www.butuan.gov.ph/home/about-butuan/general-info.html