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Keep your ear to a salt dome – 3D models visualization tools

XXI Międzynarodowe Sympozjum Solne „Quo Vadis Sal” –4-7 października 2017 r., Wieliczka

A major problem for project developers is an interactive visualization of 3D geological models that is no costly for end users. Therefore, it may be a priority to provide more solutions that allow quick access to information and look through the model of geological structures. The Polish Geological Institute - National Research Institute (PGI-NRI), as the other Geological Surveys preparing geological models, has developed its own tool on the basis of experience related to 3D geological technologies, including models of salt domes.

PGI-NRI has a 15-year experience in 3D modeling. Initially, it was used the VRML (Virtual Reality Modeling Language) standard, which allows to save three-dimensional geological structures in a compressed format that can be easily viewed in a web browser. The process of making models available through the browser is complex.

After the construction of the spatial model, topography of high resolution surfaces is generalized - upscaling is done by the applications used to develop the model, e.g. Paradigm GOCAD / SKUA, Petrel. Simplifying the model it is important to faithfully maintain the topographic features. This applies to all model elements, both stratigraphic and structural ones.

The next few years brought a new IT tools and programming languages based on the Open Source. Based on the VRML format has been created an x3D (eXtensible 3D) markup language which includes the 3D graphics.

Geometric operations in the x3D are carried out on polygons. There is also a hierarchical transformation of objects, lighting, mapping, multipass texturing, programmable pixel shading and vertices, and hardware acceleration. The x3D is designed as a versatile format for presenting scenes, in addition to graphics it allowed to support 2D vector images and a text. It is possible to define animations of objects and scenes, among others thanks to morphing. Interactivity is ensured by lifting and dragging with the mouse. There are navigations implemented in x3D – walking, flying, collision detection, objects zooming and visibility detection. Better perception of the virtual world is also possible thanks to the support of surround sound.

Technically, x3D allows scripting to dynamically change the generated environment. Scenes are or may be composed with objects that are accessible throughout the Internet, and users can move between them as on web pages, using hyperlinks. Users can create features that extend the capabilities of browsers that support the standard principles. That offers unlimited possibilities for a varied presentation of 3D models of geological structures. The management layer of the browser will be CMS (Concord Management System) - Drupal.

Based on the Geo3D browser, which is dedicated for visualization of deep geological structures developed at the University of Silesia, the PIG-PIB team decided to create a new one, being simpler with a more intuitive interface. The main purpose of the created application is to present models as a 3D block diagrams, cross sections, geological profiles and virtual drillings in the investigated deep structures area. In addition, the program allows to view other models by importing objects in VRML, .ts, and x3D formats (files generated by modeling programs such as GoCAD, Petrel and others). The program is designed to visualize 3D solids consisting of triangles, which are the basic elements of the object structure. The main window of the program contains only the elements needed to familiarize with the modeling results. Except the dialog window and the list of displayed objects there are also tools for changing the vertical scale, creating the xyz coordinate cutting maps, generating virtual boreholes and cross sections.

Building 3D browsers is a very complex multi-step process. Each model of 3D geological structure prepared by PIG-PIB provides new data that are the basis for further development of both browsers. Both described applications and the finished geological models are available on the PIG-PIB website. In 2018 will be also published the first 3D models of salt domes applied the new technology.