WorldWind Series 13: Terrain data (DEM) loading and applications (Getting started)

The loading and application of DEM in learning WW is very important for the development of three-dimensional GIS plug-in based on WW. I have always wanted to focus on and collect relevant learning materials, did not begin to study it before, mainly because I did not see the elevation of the application function in WW, feel unable to cut. I spent my time yesterday afternoon and this morning looking for research pointcuts! The essence is to find out how to view elevation in WW. (Think back now, feel a waste of time, or because I do not fully know the functions of WW)

Before I began to learn about DEM loading and application, I mainly consulted on CSDN's blog--"Celebrating, drawing out the Lod terrain grid of World Wind" (http://blog.csdn.net/paul_xj/archive/2007/08/29/ 1763585.aspx), believe that the people who study WW should have read this article and his three study summary. I have seen the study many times, combined with their own study, every time I read some harvest. His article is very concerned about the high, is definitely the WW beginners beacon. However, I will almost negate the above mentioned "the Lod terrain grid that draws world wind". I do not want users to use the text as a standard to learn WW's terrain grid (that is, the application of DEM loading), because I was also very believe that he said, according to what he said to do, the fact is not like that, I believe he is just beginning to write down, many of the things DirectX understanding is not very profound.

The so-called rendering of Lod terrain Grid has problems! How can I mix directx three-dimensional rendering with DEM in GIS? Topographic maps include topographical features and landforms. And landform is mainly embodied in contour line, in three-dimensional embodiment of DEM application (digital elevation model)! The above blog mentioned in the construction of terrain grid is only the surface rendering DirectX To line rendering, this is still flat level, there is no elevation, how is the terrain grid it?! From the perspective of DirectX three-dimensional technology, there is also a problem: DX-Side rendering and line rendering storage points are different ways, because the use of the LOD model in WW is a lot of surface rendering and adjacent, so the simple change rendering can not see the impact. But if you draw a single face and then change to a linear rendering, you'll see the problem! This is still a flat level above, surface rendering to line rendering will have problems, if it is three-dimensional objects (cubes) if the simple to line rendering, the problem is more obvious! (After you've studied DirectX, try it!) ）

As for the blog said: "Press the ' ctrl+w ' out of the grid, what is the air grid," but simply operation, magnified after seeing the "sky" behind, it is what the air grid, this is a typical metaphysical! People who have really studied three-dimensional development will know: in order to improve efficiency, three-dimensional rendering is only the front side of the rendering, not to be seen all hidden (do not render). We zoom in and see the "sky" instead of another layer of grid, because the grid behind can not be seen. ' Ctrl+w ' comes out of the grid, is a hollow sphere frame. It's just fillmode to change the DX three-dimensional sphere rendering.

Processing code in response to "Crl+w" in WorldWindow.cs:

1351 lines:

//　Control　key　down
　　　 else　if　(e.Control)
　　　 {
　　　　 switch　(e.KeyCode)
　　　　 {
　　　　　 case　Keys.D:
　　　　　　 this.showDiagnosticInfo　=　!this.showDiagnosticInfo;
　　　　　　 return　true;
　　　　　 case　Keys.W:
　　　　　　 renderWireFrame　=　!renderWireFrame;
　　　　　　 return　true;
　　　　 }
　　　 }