Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Reexamination Certificate
1998-07-13
2001-04-17
Luu, Matthew (Department: 2779)
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
C345S426000
Reexamination Certificate
active
06219064
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to features that improve the efficiency of rendering images of three-dimensional objects, and more particularly to a graphics mechanism and apparatus for mipmap level estimation for anisotropic texture mapping, wherein the mipmap estimation technique uses inverse homogenous coordinates only.
2. Description of the Related Art
Aliasing artifacts that arise due to texture mapping are well-known and have been studied by many researchers (see, e.g., [1] A. Watt, “3D Computer Graphics,” 2nd edition, Addison-Wesley, 1993 and [2] G. Wolberg, “Digital Image Warping,” IEEE Computer Society Press, Los Alamitos, Calif., 1990). Various filtering schemes can be used to deal with this problem (see, e.g., [3] F. Crow, “Summed Area Tables for Texture Mapping”, Computer Graphics, 18(3), pp. 207-212, 1984 and [4] N. Greene and P. Heckbert, “Creating Raster Omnimax Images Using the Elliptically Weighted Average Filter,” Computer Graphics and Applications, pp. 21-27, June 1986). However, by far the most popular filtering scheme is mipmapping ([5] L. Williams, “Pyramidal Parametrics,” Computer Graphics, 17(3), pp. 1-11, 1983). In this method, the original texture is averaged down to successively lower resolutions, each image in the mipmap sequence being one half of the resolution of the previous image. Then, instead of always using the original texture map, an appropriately scaled image is used.
Mipmapping as a technique has several disadvantages. The first inevitable disadvantage is an increase of memory requirements space by 33% [5]. Second, it is necessary to choose an appropriate level of pyramid each time texture mapping is applied ([6] P. Heckbert, “Texture Mapping Polygons in Perspective,” Tech. Memo No. 13, NYIT Computer Graphics Lab, April 1983 and [5]). Good selection of mipmap level is key to proper filtering and therefore is very important for image quality, as discussed in U.S. patent application Ser. No. 08/971,972, entitled “Texture Mapping With Improved Technique for Selecting an Appropriate Level in Filtered Representations of the Texture,” filed Nov. 17, 1997. Finally, the third disadvantage is due to the possible anisotropy artifact, because, by original construction, mipmapping cannot adequately handle situations where the ratio of either texture or screen dimensions of a surface is significantly different from one.
Various texture mapping techniques have been proposed. For the most part, these techniques do not compute mipmap levels and/or do not address the issue of anisotropy. One such technique is set forth in U.S. Pat. No. 5,224,208. This technique is embodied in a method and apparatus for calculating the gradients of texture map parameters in perspective space. The technique provides a way to calculate a texture gradient in the direction of viewing. This gradient is then used to calculate a pre-filtered textured value. This approach is dependent on viewpoint distance but has a relatively complicated implementation scheme and also does not address texture anisotropy.
OBJECTS OF THE INVENTION
Therefore, it is an object of this invention to overcome the aforementioned problems.
It is another object of this invention to provide a technique for computing mipmap levels based on inverse homogenous coordinates only.
It is a further object of this invention to provide a mipmap estimation technique using inverse homogenous coordinates which also takes into account texture anisotropy, thereby eliminating the need for complicated anisotropy processing.
SUMMARY OF THE INVENTION
In one aspect of the invention, a method is provided for selecting a mipmap level for each pixel in an object, in world and screen coordinate space, with compensation for an anisotropy effect. The method comprises the following steps: calculating, for the entire object, in world coordinate space, a binding anisotropy coefficient; calculating a first value as a minimum of a function that defines a mipmap level for the entire object as a function of a viewing transformation angle; assigning a value of the function as the first value, if the binding anisotropy coefficient is larger than a critical number such that the binding anisotropy is so high there is no practical solution to minimize; calculating an angle of viewing transformation, if the binding anisotropy coefficient is smaller than the critical number; calculating a second value indicative of the current mipmap level; calculating, for each scanline, an inverse of a first homogeneous coordinate of the corresponding scanline and an inverse of a last homogeneous coordinate of the corresponding scanline; calculating, for each pixel of each scanline, an inverse homogeneous coordinate by interpolating the inverse of the first homogeneous coordinate of the corresponding scanline and the inverse of the last homogeneous coordinate of the corresponding scanline; and calculating the level of the mipmap as a function of at least the calculated inverse homogeneous coordinates.
The method may be embodied in the form of software that may be stored on an appropriately configured computer system. Such software may also be stored on a computer usable medium such as a floppy disk or CD ROM and may transferred to a suitable computer system for execution. The method may also be embodied in the form of hardware that is incorporated into an appropriately configured computer system.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5220650 (1993-06-01), Barkans
patent: 5224208 (1993-06-01), Miller, Jr. et al.
patent: 5287442 (1994-02-01), Alcorn et al.
patent: 5307450 (1994-04-01), Grossman
patent: 5519823 (1996-05-01), Barkans
patent: 5566284 (1996-10-01), Wakayama
patent: 5594846 (1997-01-01), Donovan
patent: 5594854 (1997-01-01), Baldwin et al.
patent: 5606650 (1997-02-01), Kelley et al.
patent: 5706481 (1998-01-01), Hannah et al.
patent: 5710879 (1998-01-01), Ashburn
patent: 6005582 (1999-12-01), Gabriel et al.
patent: 6008820 (1999-12-01), Chauvin et al.
IEEE Computer Graphics & Applications, J. Blinn, “Hyperbolic Interpolation”, pp. 89-94, Jul. 1992.
Computer Graphics, F. Crow, “Summed-Area Tables For Texture Mapping”, vol. 18(3), pp. 207-211, Jul. 1984.
IEEE Computer Graphics & Applications, P. Heckbert, “Survey of Texture Mapping”, pp. 56-67, Nov. 1986.
IEEE Computer Graphics & Applications, N. Greene and P. Heckbert, “Creating Raster Omnimax Images From Mulitple Perspective Views Using the Elliptical Weighted Average Filter”, pp. 21-27, Jun. 1986.
Addison-Wesley Publishing Company, A. Watt and M. Watt,“Advanced Animation And Rendering Techniques”, pp. 140-148.
Computer Graphics, L. Williams, “Pyramidal Parametrics”, vol. 17(3), pp. 1-11, 1983.
IEEE Computer Society Press, Los Alamitos, California, G. Wolberg, “Digital Image Warping”, 1990.
Proc. 1997 Siggrraph/Eurographics Workshop on Graphics Hardware, A. Barkans, “High Quality Rendering Using the Talisman Architecture”, pp. 79-88, Los Angeles, 1997.
Kamen Yakov
Shirman Leon
Cunningham G. F.
Luu Matthew
Seiko Epson Corporation
LandOfFree
Graphics mechanism and apparatus for mipmap level estimation... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Graphics mechanism and apparatus for mipmap level estimation..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Graphics mechanism and apparatus for mipmap level estimation... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2543038