NDLI: A terrain and cloud computer image generation model

Content Provider	ACM Digital Library
Author	Dungan, William
Abstract	A method is presented that produces a realistic simulation of terrain using source data from the Defense Mapping Agency (DMA). Spatially compact objects are presently modeled with some success at realism. Because terrain is large in extent it exhibits special problems. These problems include: data base size and generation, masking priority, and shading. An array of height values can be created from the DMA terrain file. Height is a single valued function of the array coordinate pair. The pair has implicit positional information. A masking priority algorithm is used which has no restriction on observer geometry. The algorithm searches the height array along the line of sight for the first visible position in the array. This approach requires no clipping or depth sorting of surface representations. The height array indices are used to access the pixel shade from a registered, orthonormal texture array. The use of texture provides a simple way to add nonlinear shading for a realistic representation with flexible data base generation. Atmospheric attenuation is a method used to increase realism. Methods are in use which produce haze or fog with constant attenuation. The line-of-sight search is used to produce realistic clouds with spatially variable attenuation. Terrain and clouds are adequately simulated using this method of modeling. The data structures of height and texture arrays are simple, easily generated, and make good use of storage resources. Resolving masking priority along the line of sight is a visible surface algorithm which has advantages over hidden surface algorithms. Realistic representations such as texture and atmospheric attenuation are used with some success.
Starting Page	143
Ending Page	150
Page Count	8
File Format	PDF
ISSN	00978930
DOI	10.1145/965103.807436
Journal	ACM SIGGRAPH Computer Graphics (COMG)
Volume Number	13
Issue Number	2
Language	English
Publisher	Association for Computing Machinery (ACM)
Publisher Date	1988-08-01
Publisher Place	New York
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Shadows Masking priority Clouds Computer graphics Atmospheric attenuation Terrain model Texture Data base Fog
Content Type	Text
Resource Type	Article
Subject	Computer Science Computer Graphics and Computer-Aided Design

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
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3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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