Rendering objects over large distances is common for geospatial programs, and when done incorrectly, the objects may visually jitter. Here, an object is made up of any combination of triangles, lines, and points, like a 3D model. The problem becomes more noticeable as the viewer nears the object. The following video demonstrates this using STK. (Note that I had to modify STK as it does not ordinarily exhibit jitter.)
Rotating about the space shuttle from far away, there is no jitter. After zooming in, the jitter is readily apparent. In this blog entry, I'll discuss the cause of this problem and the solutions used in Point Break and STK.
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In Point Break, primitives form the building blocks of a 3D scene. Developers create primitives and initialize them with information, such as position and attitude. Primitives then take care of all the 3D rendering (drawing) and optimizations, allowing developers to focus on their application code.
An abridged set of primitives planned for Point Break include:
- Models – Support for the industry standard COLLADA format and AGI’s MDL format.
- Markers –2D images that always face the viewer and remain a constant pixel size. Markers are commonly used to visualize a large number of tracks moving in real-time.
- Polylines – Used for rendering lines on the ground or in space. Polylines are used to visualize many things including country borders, drop lines, range rings, and access lines. Polyline variants can conform to terrain when drawn on the ground.
- Triangle Meshes – The rendering workhorse for things such as area targets (e.g. states or countries), terrain and imagery extents, ground ellipses, and border walls. The surface mesh, a triangle mesh variant, can conform to terrain when drawn on the ground.
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