Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Patent
1998-03-16
2000-05-16
Powell, Mark R.
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
345431, 345432, G06T 1560
Patent
active
060643927
ABSTRACT:
The present invention simulates the effect of non-homogenous fog in computer graphics images. The non-homogenous fog visibility equation includes four parameters. A distance scaling parameter K1. A variable fog parameter K2. A normalization constant K3, and a scaling constant K4. The visibility at a sample point can be determined using the visibility equation: ##EQU1## where Z.sub.ns is a normalized and scaled image distance which is equal to (K4*K1*Z)+(K4*K2). To improve computational efficiency the visibility function can be evaluated using a lookup table. The lookup table of the present invention has an efficient addressing scheme and a minimum number of output steps. The visibility function can be expressed as a function of a fog ratio and a fog distance. The fog distance is a distance from the viewpoint to the point where the visibility is reduced to 37% of full visibility. The fog ratio is the square root of the ratio of "near fog" density to "far fog" density. The visibility function expressed as a function of fog ratio and fog distance is ##EQU2##
REFERENCES:
patent: 5363475 (1994-11-01), Baker et al.
patent: 5412796 (1995-05-01), Olive
patent: 5535374 (1996-07-01), Olive
Open GL 1.1 Webpage reference, Jan. 28, 1998.
Schumacker et al., "Low Visibility Effects for Computer-Generated Image Systems", SID Symposium, pp. 70-71, May 1971.
Neider et al., "OpenGL Programming Guide, The Official Guide to Learning OpenGL, Release 1", Open GL Architecture Review Board, pp. 216-223, Aug. 1994.
Caserza Steven F.
Good-Johnson Motilewa
Oak Technology, Inc.
Powell Mark R.
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