Workflow for Interactive High-end 3D Visualization in Site Planning

Transcription

1 Workflow for Interactive High-end 3D Visualization in Site Planning Rüdiger MACH Introduction High-end visualization is fun, it looks good and is convincing. But more important for engineers, architects and planners is the fast, efficient, attractive and correct visualization of all kinds of design data during the planning process. Grand scale construction projects are very expensive. Insufficient coordination during the planning phase, planning mistakes and the human factor will produce additional costs, which are usually not taken into account beforehand. The early use of interactive 3D visualization can help to avoid some of these sources of errors. One needs tools which are able to combine all kinds of required data: landscape, terrain and design data have to be visualized quickly and efficiently globally and locally. Data import and navigation have to be as simple as possible. A very important detail is that specialists as well as non-specialists must be able to explore the data. This article shows the workflow of pre-visualization of planning data using the TerrainView Product Suite. 1 A Communication Platform? Conveying large planning schemes, which are geo-referenced, is the primary objective. Bringing together the plans in good time can help to support critical decisions and to communicate complex ideas quickly and efficiently. The mixture of data which is created in planning has to be preprocessed quickly and efficiently and has to serve as a basis for time-critical discussions. For this, one needs a communication platform, which enables the integration of diverse data without requiring specialist knowledge. Bringing design data together at an early planning stage may facilitate the decision-making process in complex projects. For big projects in the process of planning, the right communication platform can save expenses and trouble. 2 General Requirements There are considerable requirements, and the fields of implementation are very complex in as broad a subject as this. Diverse programs and methods at the start of a project or plan place extremely high demands on shared data interfaces and the possible integration of data.

2 338 R. Mach CAD programs, such as AutoCAD, Microstation, Allplan and Vectorworks are used, as well as diverse add-on products, such as Civil3D (AutoCAD) or Inrail (Microstation). Many a planner chooses GIS tools like Esri s ArcGIS or Manifold from the start. These programs produce data formats which can seldom be represented without problems in Real Time visualization environments. Such basic data usually consists of: 1. GIS data Imagery, Elevation, Vector and Annotations 2. Planning data to integrate 3d models like: Buildings, Technical detailed constructions and Local elevation models (reduced to a small area). The quality of visualization can vary considerably and it is hard to find the tool which meets one s needs precisely. It depends on the objectives of the project. Some general demands on Real Time visualization might be described as follows: 1. Representation of unchanged geometry There must be no polygon reduction; if this is unavoidable, it has to remain controllable. 2. Integration of large textures These are aerial pictures or other textures compressed without loss. 3. LOD - Level of Detail Elements beyond a defined distance from the camera are simplified. 4. Velocity Fast and easy navigation within the VE (Virtual Environment). 5. Actions/Behavior The option to include links and special behavior like collision or intersection detection. 6. Operation/Navigation Easy use of navigation elements. 7. Platform/Presentation Platform independence. 8. Data transfer Data interface for the most commonly used programs. These points refer to the requirements of viewing large-scale data, and to the interaction with this data in an IE (Interactive Environment). 3 Trends and Problems There is a trend towards using special interactive 3 dimensional applications (BUHMANN, PAAR, BISHOP & LANGE 2005). It makes sense for users to be able to navigate on their own, be it when using a communication platform for specialists or simply a medium for presentation. Interaction encourages learning, as the user is able to experience an environment at a speed and in a way that suits himself; it reduces the user s inhibitions to use certain software, and enables further discussions between colleagues (SHNEIDERMANN, MACKINLAY & CARD 1999).

3 Workflow for Interactive High-end 3D Visualization in Site Planning 339 In this context, special attention can be placed on so-called Virtual Globe applications. The complex and interesting fields of application of virtual globes are: Planning/engineering/architecture Cartography and navigation Research and development Petroleum, electricity and gas industries Tourism Insurance Television/broadcast Crisis and catastrophe management Three aspects hinder the quick and efficient use of visualization tools in the field of planning. Two of these aspects are when using geo-referenced data the right reference system, and the definition of the units used in planning. Here, still, it is necessary to communicate clearly which co-ordinate or projection system is to be used, and of course, which units are in use or whether one is working in meters, centimeters or millimeters. 4 Virtual Globe? While the idea was already presented in 1992 by Neal Stephenson 1 in his novel Snow Crash, the real concept of virtual globe is relatively new, and is only now starting to become established in the minds of users and specialists. Already in mid-2003, supplementary to its GIS application ArcGIS 2, ESRI brought out the application ArcGlobe. TerrainView-Globe 3 which is specialized for commercial professional solutions, was released in Leica 4 developed the Virtual Explorer, Microsoft is concentrating on MSN Virtual Earth 5, Skyline is selling Skyline Globe 6, NASA has made its product WorldWind 7 freely available, and probably the most well known version of a virtual earth is Google Earth 8. A virtual globe application is a program or system which is able to represent diverse forms of 3D, elevation, imagery and vector data interactively in a global context. Usually, a global co-ordinate or projection system is used, such as WGS84 9. If arbitrary planets are to be represented, one refers to them as virtual globes, whereas a representation of the earth is called a virtual earth. This spontaneously makes one think of the term GIS, or Geographic Information System. A GIS is certainly the right tool to use in order to utilize and analyze such large amounts of data. It is, however, not able to show 3 dimensional data in real time. Large data banks and

4 340 R. Mach virtual reality applications are not very compatible. However, a virtual globe application enables the user to move through the scene as if it were a scene from a computer game. A detailed description of virtual globes can be found on Virtual_globe. Compared to the requirements for pure real time environments, following points remain for the use of virtual globes: 3D Geo content the system must be able to process and represent well-established earth data and supplementary geo information such as elevation data, imagery, vector declinations / surfaces and annotations. 3D models supplementary 3D models are an important aspect when creating convincing visualizations. Examples of these are buildings, landmarks, city models, vegetation etc. Navigation the navigation should be simple and intuitive, and options such as walkthrough, flythrough or target search are desirable. Navigation additions creating POIs (Points Of Interest) and flight paths helps the user to find additional and describing information Streaming the Internet enables the quick and distributed access to large amounts of data. Therefore, the data should be able to be optimized for streaming. Integration the importing of arbitrary data streams (e.g. GPS data or movement data) which can be interfaced with a virtual globe with 3D models or arbitrary information. 5 TerrainView-GlobeTM TerrainView-Globe is a part of the TerrainView product suite of the Swiss company Viewtec AG, and it is the advanced version of the product TerrainView, which was originally developed as a VR viewer and editor. Detailed information can be found at 6 Constituent Parts and Practical Use TerrainView-Globe has a special mixture of dealing with the previously mentioned diverse kinds of 3D data from GIS and planning. GIS data can be used for global or very large sets of data, and arbitrary 3 dimensional planning data can be mixed into these environments as well (MACH 2007).The great advantage of this application is that diverse data can be brought together and can be visualized at the start of a project without too much effort. This provides a communication platform, which enables one to view complex plans quickly and easily, and to check for flaws or weak spots. 7 Workflow The workflow of TerrainView-Globe is simple and uncomplicated. A mixture of data, consisting of 3D data for models, geo content and descriptive information can be optimized and edited for the streaming rendition.

5 Workflow for Interactive High-end 3D Visualization in Site Planning 341 The program supports co-ordinate and projection systems, current height, image and vector formats, as well as the most commonly used 3D formats. This guarantees that just about any geo-referenced data set has a place on the global platform. If the data is not geo-referenced, data can also be freely positioned and shifted about. Additional 3D objects, height, image and vector data can be downloaded or imported. All data can be switched on or off in a special layer technique, or be blended into each other. 8 Geo Data The following Figure 1 shows the data set which serves as the basis for the earth, which is based on World SRTM 90 m 10 for the elevation data, as well as NASA Blue Marble Next Generation 11 with a resolution of 500m per pixel. Fig. 1: Screenshot TerrainView-Globe

6 342 R. Mach When geo-data is imported, it not only gets downloaded into a scene, it is also optimized for use in a virtual reality environment. This means that it is adapted and tiled with special LOD 12 -Algorithms in such a way that a web stream with a repeat rate of up to 60 fps 13 is possible. This kind of conversion is applied to elevation data, imagery, vector data and additional information. The processing of this data solely takes place in the integrated pre-processor. However, the importing of data does take a little longer, as the data has to be re-projected from the co-ordinate system at hand to WGS84. Ideally, the data is already in the appropriate system to start with. Figure 2 shows the geo data set which has been imported additionally to the earth data set. Fig. 2: Screen shot with an example of an imported geo data set consisting of an elevation model and the corresponding aerial photograph. The background shows Switzerland with an aerial photograph and a topographical map. ( Swisstopo 14, 25 m DEM) The two maps can be blended into one another like layers in Photoshop. 12 LOD Level of Detail. 13 fps Frames per Second. 14

7 Workflow for Interactive High-end 3D Visualization in Site Planning Terrain Model as an Object in 3D Any arbitrary digital terrain model which is available in one of the commonly used 3D formats is opened via the file menu. Formats which are supported are listed in the appendix. In this case, the terrain is treated like a 3 dimensional object (Fig. 3), and can be switched on or off as necessary. Fig. 3: Screen shot with an example of an imported geo data set. ( Swisstopo) Additionally, this data set was prepared in 3ds Max and downloaded as a 3D object via the ViewTec IVC plug-in. 10 3D Object In any 3D application (CAD, visualization) such as AutoCad, Civil 3D, Allplan, 3ds max, Cinema4D or Softimage, a 3 dimensional subject matter is created and edited. Depending on the effort required, this 3 dimensional subject matter can be optimized especially for the needs of 3D interactive applications. An appropriate optimization, for instance Texture Baking with light and shadow information, varies depending on the application, and the description of this will not be

8 344 R. Mach Fig. 4: The figure shows a pre-planning state of power lines. The digital elevation model is based on an ArcGIS ASCII grid, the power lines have been build in AutoCAD ( Swisstopo 15, 25 m DEM, Atel Schweiz 16 ). discussed in further detail here. Figure 4 shows a screenshot of a project, where the location of power lines had to be discussed. 11 Data Formats supported in TerrainView-Globe Digital Elevation Models Arc/Info ASCII Arc/Info Binary (.adf) USGS SDTS DEM (*CATD.DDF) TIFF/GeoTIFF (.tif) Military elevation data (.dt0,.dt1) USGS ASCII DEM (.dem) Atlantis MFF VTP Binary Terrain Format (.bt) Image Formats ERMapper Compressed Wavelets (.ecw) TIFF/GeoTIFF (.tif)

9 Workflow for Interactive High-end 3D Visualization in Site Planning 345 Erdas Imagine (.img) JPEG2000 (.jp2,.j2k) JPEG JFIF (.jpg) Multiresolution Seamless Image Database (MrSID) Vector Formats and Annotations Arc/Info Binary Coverage ESRI Shapefile Mapinfo File Microstation DGN U.S. Census TIGER/Line 3D Formats ViewTec IVC Multigen OpenFlight OpenScenegraph IVE, OSG Carbon Graphics GEO CyberCity FLT, IVC Autodesk 3DStudio 3DS Autodesk 3D Studio Max (for versions 6,7,8 ViewTec Plug-In which is free of charge is necessary) VRML 2 WRL Design Workshop DW Alias/Wavefront OBJ NewTek LightWave 3D LWO Controls and Navigation The surface is intuitive and easy to use. The view mode is active by default. This enables a free navigation through and over complex 3D environments. Further navigation modes such as Flight Mode, Explore Mode or Low-Level Mode make advanced maneuverability within the scenes possible. Extra Features Some extras, which are interesting for visualizers, are the creation of POIs (Points of Interest), flight paths, the possibility of crating an unlimited amount of screen shots, the output of HDTV film material, and a convincing weather engine, 3D objects can be switched on or off. Studies in variation are therefore simple to operate and execute. 12 Summary and Conclusion Data volumes are increasing, and in fields like catastrophe management, large construction projects and planning, new tools are necessary to be able to view and present this data at early planning stages. The classical 3D animation is too time consuming and the games industry and new media have increased the demands of viewers and changed their viewing habits.

10 346 R. Mach TerrainView-Globe fills a niche in the field of highly complex virtual reality applications for technically demanding issues. Security-sensitive and complex data can be processed and visualized using this platform exceedingly quickly. Simple to handle and quickly fed with the required data, this is a tool which more than fulfils the needs caused by today s data volumes. References Buhmann, E., Paar, P., Bishop, I. D. & Lange, E. (Eds.) (2005), Trends in Real-Time Visualization and Partizipation. Proceedings at Anhalt University of Applied Sciences Wichmann, Wichmann, Heidelberg. Mach, R. (2007), Virtual Globes. In: Digital Production, 1/2007 Shneidermann, B., Mackinlay, J. & Card, S. (1999), Readings in Information Visualization (1 st edition). Morgan Kaufmann Publishers. Software Homepage of TerrainView