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| Featured Articles |
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| SuperGIS Globe Image Processing Technology |
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The display of visual effect matching the rich interface of map information has always been the most attractive way to draw peoples attention. Particularly, in recent years, the launch of huge image platform webs and the applications of other 3D and Virtual Reality practices have grown more and more popular; therefore, the 3D GIS technology gradually becomes a hot field.
Since the GIS development began in 1970s, 2D display have been the mostly used manner in the display of transforming real world into an easier acceptable and expressive graphic model. However, due to the mature 3D computing capabilities and the greatly improved internet service transmission speed, the technologies of 3D GIS data display have become increasingly mature. Therefore, it would no longer be a tough task to display various forms of geographic information in 3D display or processing. |
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| SuperGIS Globe is the application interface to SuperGIS 3D analyst, which enables users to inspect or analyze GIS data in 3D manner. To the 3D image display technology, the biggest problem is how to present with smooth visual effect and keep the display performance, which is also the key technical problem faced by image data combined with 3D environment display. To solve this problem, SuperGIS Globe has adopted two sorts of image display technologies, Level of Detail (LOD) and Fade-in processing, for the improvement of 3D display performance on GIS image data and the visual present effect.
Level of Detail (LOD) and Fade-in processing are going to be introduced respectively in the following section. |
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| Level of Detail (LOD) |
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| As rendering real-time 3D view in a computer, if you want to smoothly alternate the views by observing at different angles, it takes dynamic transformative calculation to the overall data. However, the skeleton of 3D model and light source already take huge system capacity, not to mention the GIS part has even huger capacity in at least GB (Gigabytes) or even TB (Terabytes) scale. Therefore, if users want a speedy and simultaneous processing, the performance will work extremely poor. In such case, Level of Detail (LOD) is exactly the key technology to solve the performance problem on 3D computer rendering. Similar to 2D Image Pyramid technology, Level of Detail (LOD) classifies the 3D data into several levels of different details. To data of huge range and in long distances, only the small volume of the simplified data is processed to respond to the speedy alternative views during manipulation so that the delay caused by late calculation can be prevented. On the other hand, to data in short distances and under still manipulation, in order to display in better quality, the Multi-Threading will be used to gradually process the high-precious data with longer time so that the smooth dynamic manipulation and artistic still views could be both achieved. |
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| Fade-In Processing |
| The overlapped data of different LOD will cause apparent merging seams. Therefore, SuperGIS Globe decides to adopt the Fade-in technology to solve this problem. The core Direct3D renderer engine can dynamically modify the transparency by adjusting \ value of the image and produce the special visual effect for image display (NB: the content of \ value records the transparency of an element). As a result, when data of high LOD merge data of low LOD, the display will be presented in half-transparent effect from light to deep degree gradually. Thus, the overall display will look much smoother, and the merging seams will be eased effectively. |
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Fade-in processing allows that the display of LOD in different levels can be merged more smoothly without apparent seams. |
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