Study on the Key Technique of the Hill Shading Virtual Roaming System Based on XNA - Advances in Image and Graphics Technologies - page 230

Study on the Key Technique of the Hill Shading
Virtual Roaming System Based on XNA

Hesong Lu, Zaijiang Tang, Qiang Liang, and Wei Shao

Simulation Center, Academy of Armored Force Engineering, No. 21 Dujiakan,
Fengtai District, Beijing, China
[e-mail]

Abstract. It is helpful for people to understand the undulating topography with
hill shading map. In this essay, we focus on how to shade the terrain blocks
with XNA Game Studio3.1 by using the global DEM data from geographic
information public service platform set as the data source. Including LOD
structure, constructing a TriangleStrip terrain block model, applying HSV color
model to color vertices, using XNA default lighting model and adjust relevant
parameters to generate shading effect. Finally, a global height-color mapping
table designed was offered, the represented effects of prototype system were
also showed.

Keywords: XNA, DEM, hill shading, LOD, HSV color model and roaming
system.

1 Introduction

The event of Malaysia Airlines MH370 aircraft lost made us realize that we have
limited understanding of world geography. Digital Earth and other related public GIS
products such as Google Earth in virtual reality did very well, but the lack of hill
shading terrain roaming function still needs to be developed. The hill shading method
is crucial to produce the three-dimensional effect of topography on the map [1].
Making hill shading map is one of the basic functions in GIS, but they lack the large
terrain roaming capabilities or must be online to use. TIANDITU website v2.0
supports browse hill shading map, but does not support the use of 3-D hill shading
terrain roaming.
The 3D terrain visualization technology is widely used not only in GIS and virtual
environment simulation but also in 3D computer games. The XNA Game Studio is a
game development kit designed by Microsoft for independent game developers.
Compared to DirectX and OpenGL, XNA meets the functional requirements of the
system and is more efficient. The geographic coordinate system of the DEM data used
in system is WGS-84. It is a right-handed coordinate system, and the default
coordinate system in XNA is right-handed. The prototype system developed the XNA
Game Studio 3.1.
The rest of this essay is organized in the following ways: Section 2 introduces the
LOD structure in brief; Section 3 contains the description of the terrain block model;