Introduction to 3D Data

Introduction to 3D Data

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  Introduction to 3D Geovisualization John Reiser
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  History • Computer renderingof 3D images is a relatively recent development. • 3D rendering requires considerable processing to generate photorealistic images. • Until capabilities rose and costs dropped, 3D rendering was often a task left up to supercomputers. • One of the first 3D models: “Utah Teapot”
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  Utah Teapot • Designedand rendered by Martin Newell in 1975 at the University of Utah. • A standard white Melitta tea pot. • Originally didn’t have a bottom. • Reference data for testing new applications.
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  3D Rendering • Let’s cover some basics behind 3D rendering. • Several methods for drawing the 3D object. • Constructing a model out of triangles. • Rendering methods can be refined further with textures and lighting effects.
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  Wireframes • Most basicmethod of rendering a 3D object. • Vector representation of a 3D object from a specific vantage point. • Edges are shown with simplified faces.
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  Textures • Textures areapplied to the faces of a 3D model. • Textures can be a solid color, image or photograph. • Textures can include additional data, such as noise, reflectivity or bumps.
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  Raytracing • Rendering method employs algorithms to simulate individual rays of light and how they interact with the object and the environment. • Light, shadows, focus, etc can be modeled. • Highly photorealistic.
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  Polygon Rendering • Theedges and faces are • Stanford Bunny essentially 3D polygons. 69,451 polygons. • The more complex the polygon, the longer the rendering time. • The simplest polygon is the triangle. • Many renderers utilize triangles to construct a 3D model.
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  Triangles & TINs •Back to GIS, triangulated irregular networks are digital elevation models based on nodes & edges that form a mesh of triangular faces. • Rendering landscapes instead of objects requires georeferencing.
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  TINs versus RasterDEMs • TINs allow for greater variation in the terrain than raster. • Raster cell sizes must be small to capture minute variations, producing larger files. • Gentle changes need only a few triangles to be represented.
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  Building Models • Wireframemodels can be covered with an architectural rendering or a photograph to create a basic building model. • Details can be introduced by adding more textured faces to the volume.
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  Building Information Modeling •Highly detailed models of buildings, down to interior spaces. – HVAC, mechanicals, etc. • Used for facilities management. • Used to visualize maintenance, planning and construction efforts. • GIS for buildings.
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  Viewing 3D • Severalmethods of viewing 3D images on a 2D surface. – Shutters – Anaglyphs – Free (cross eyes) • Some 3D rendering software will create anaglyphs for you.