In: Wagner W., Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
674 
LUNAR GEOMORPHY 3D VISUALIZATION METHOD 
Z. Yang, X. Qing, Z. BaoMing, L. JianSheng, L. ChaoZhen 
Institute of Surveying and Mapping, ZhengZhou 450052, China - Zhouyang3d@163.com 
KEY WORDS: Lunar exploration, Moon Image, Moon DEM, Level of Detail, Visualization 
ABSTRACT: 
Based on research of large-scale terrain visualization methods, we improve the planar Geometry Clipmaps method 
by making use of GPU Vertex Processor to projection transform planar terrain into spherical terrain, spherical 
view culling and spherical viewpoint controlling . We collected and deal with the lunar image and DEM to render 
the lunar 3D map. The results show that the rendering algorithm’ efficiency is independent on datum but there is 
distort problem in Lunar Pole. 
1 INTRODUCTION 
Back to Moon, building Lunar base and exploration 
Lunar resources have been the trend and hot dot of 
international spaceflight. Lunar exploitation is the first 
step of Chinese deep space exploration missions. The 
successful launch of ChangE No.l satellite indicated 
that china have the ability to explore the deep space. 
Obtain lunar remote image and 3D physiognomy data 
in satellite remote and surveying technology and 
rendering the 3D map in 3D visualization technology 
is the one of main tasks of ChangE No.l satellite. In 
this paper, based on the research of large range terrain 
visualization algorithm, we improved the Geometry 
Clipmaps algorithm and the planar terrain be 
transformed to the spherical terrain with GPU shaders. 
We collect the lunar image and DEM and rendered the 
lunar 3D map by use of the spherical view culling 
technique and spherical viewpoint control technique 
to assist human to know well the moon. 
2 PREVIOUS WORK 
2.1 The terrain render algorithm 
A primary difficulty in terrain rendering is displaying 
realistic terrains to the user at real-time frame rates. 
Several terrain-rendering techniques have been 
proposed that use Level of Detail (LOD) to generate a 
simplified representation of a terrain. 
Previous publications and applications can be divided 
into two parts: Those with static level of detail 
(S-LOD) and continuous level of detail technique 
(C-LOD). 
(1) S-LOD technique 
Here the terrain is divided into tiles each of which is 
represented by a set of TINs with varying resolutions. 
Depending on the distance to the viewer for each tile a 
TIN with appropriate projective triangle size is chosen 
from the set. If regularly coarsened meshes are used 
instead of TINs the method is called geo-mipmapping 
m . 
(2) C-LOD Algorithms 
The most elaborate terrain rendering technique known 
today is the continuous level of detail technique 
(C-LOD). It improves the sub-optimal approximation 
quality of the S-LOD algorithms in a sense that the 
triangulation is altered on a per triangle and not on a 
per tile basis. This allows much better approximations 
which adapt optimally both to the viewing distance 
and to surface roughness. 
Several main C-LOD algorithms include Lindstrom [2] , 
Duchaineau [3] , Roettger [4] , and Losasso [51 . 
The geometry clipmap is a recently proposed 
approach that utilizing the potential of modem 
graphics hardware. The Algorithm caches the terrain 
in a set of nested regular grids centered about the 
viewer (fig 1). The grids are stored as vertex buffers 
in fast video memory, and are incrementally refilled 
as the viewpoint moves. This simple framework 
provides visual continuity, uniform frame rate, 
complexity throttling, and graceful degradation 161 . 
Those algorithms mentioned in previous section deal 
with planar terrain. Clasen describe a terrain rendering 
algorithm for spherical terrains based on clipmaps[7]. 
The algorithm replaces the underlying geometry with 
one that maps better to the sphere. No matter how far 
away the viewer is relative to the planet, he cannot see 
more of it than one hemisphere. So the algorithm uses 
concentric rings instead of rectangles. The resulting 
spherical Geometry Clipmap is displayed in fig. 2.