Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
1999-08-06
2001-12-04
Luu, Matthew (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
C345S581000, C345S584000, C345S587000, C345S585000, C345S588000
Reexamination Certificate
active
06326976
ABSTRACT:
TECHNICAL FIELD
The present invention concerns a method for determining the representation of a picture on a display and a method for determining the color of a pixel displayed on a display.
BACKGROUND OF THE INVENTION
It is well known to have pixel representations of pictures having a better resolution than the display they were displayed on. Further it is well known to compute a representation from a picture according to a given viewers position and a given viewers direction in order to display an image on a screen which corresponds to the picture seen under the given conditions by a viewer.
It is a popular and well known method of picture representation to decompose it in a polygonal model. The surface of each polygon is filled by a so-called texture. The details in representation of a picture were growing with an increased amount of pixels representing such a texture. On the other side the time needed to calculate the representation of the texture on the screen increases with the amount of the pixel size of the picture. Especially when a real time representation of the picture is required huge calculation capacity and great memory storage were required to deal with big pixel sizes of the map, which is too expensive for ordinary computer users.
Texture mapping is a popular way of enhancing realism of three-dimensional scenes without increasing the polygonal complexity. Usually, system memory or memory dedicated as texture memory is restricted by technical and/or economical constraints. On specialized computers with high graphic abilities, the size of a single texture is limited to a resolution in the order of 1,024×1,024 pixels. High resolution graphics are graphics representing pictures wherein a great amount of detail has to be represented. Textures were required having a resolution of 10,000×10,000 pixels or more. It is impossible to use directly known and usual graphic workstations to render such textures on the terrain in reasonable time.
In the area of texture mapping, filtering techniques have been developed to adapt the pixel size used in object space to the pixel resolution of the projected pixels in the display space. A hierarchy of images is generated from the original texture using so-called MIPmap pyramid. This well known and widely used filtering method is described in L. Williams, “Pyramidal Parametrics”, in Computer Graphics (SIGGRAPH 1983 proceedings), July 1983, pp. 1-11.
Further mapping textures under surfaces of computer generated objects with prefiltered MIPmap data leads by reducing the pixel size of the texture to an effect called aliasing, which aliasing gives to the viewer an impression of a blurred image on the display.
SUMMARY OF THE INVENTION
It is the object of the present inventions to enable computers disposing of a relatively low capacity for calculating the displayed image to fast and unalterated representations of images disposing of textures with a large size.
According to the present invention a picture is defined in an object space with a certain high resolution. The picture itself is described as a polygonal model of the structure of the picture and a number of textures filling the surface of the polygons. To each polygonal surface a texture is associated. The representation of a projection of the object space in the image space is calculated depending on a given viewers position and on a given viewers direction. The representation of the projection of the object space on the image space is displayed on a display. The display disposes of a defined resolution given by the amount of pixels in height and width of the display. The textures were represented by a multilevel parameter MIPmap. In order to determine the level of the MIPmap of a texture at which the texture has to be displayed on the screen a bounding box containing the considered polygon in object space is determined. Then a representation of the bounding box in the image space of the display is determined and the amount of pixels on the display covered in height and width by the bounding box in the image space of the display is determined. The maximum of the amount of pixel is determined and rounded up to a power of 2. The so determined power of 2 is the level at which MIPmaps of the texture of the considered polygon were useful representations of the picture on the display.
This allows to minimize the amount of data having to be stored in the memory used for the display without unduly limiting the resolution of the picture displayed. Further advantageous reduction of calculating time or storage memory required for displaying textures is described in the methods according to the claims
2
to
8
depending on claim
1
.
In the independent claim
9
a method is claimed for determining the color of a pixel displayed on a display. Such method reduces a blurred image effect due to aliasing during mapping a texture and thereby reduces the resolution of the texture to a lower resolution.
When it is spoken of the color of a pixel it is both possible to consider color and black and white or gray scale pictures. Black and white is a representation wherein only two color values exist. A pixel is either black or white. A gray scale representation is a representation wherein the color values are only mixed out of black and white. True color representations were representations according to the pixel color values of fixed or variable bit length of three base colors. Other methods to define the color of a pixel on a display may also associate a color value to a pixel.
As a language convention the pixels representing an image in an object space not displayed on a display but stored in a memory are often designated with the term “texels” in order to differentiate them from screen pixels effectively displayed. According to claim
9
of the present invention is a method which determines, depending on the maximum amount of texels which may be considered for calculating, the color value of a pixel. The maximum amount of texels which may be considered depends on the limitation in the calculation speed of the processor used and other hardware or software limitations of the system used. The maximum number of color information the system is able to deal with is used to determine the color of a displayed pixel. The color value of a pixel is determined by calculating a weighted average of color values of an amount of texels. The amount of texels which has to be considered is determined by determining the so-called footprint of a pixel in the object space of texels, the footprint of a pixel being the amount of texels projected on one and the same pixel displayed. Then the aspect ratio of the bounding box of the footprint is determined by the length and width of the bounding box. The maximum value of the MIPmap level associated to the width of the bounding box and the length of the bounding box is determined using the aspect ratio of the bounding box and the maximum value of texels which may be considered. The integer value of that maximum is defining a MIPmap level. That so defined MIPmap level is used to build the weighted average of the texture.
The claims
10
to
14
describe further advantages developments of the method according to claim
9
.
REFERENCES:
patent: 5097427 (1992-03-01), Lathrop et al.
patent: 5579456 (1996-11-01), Cosman
patent: 5760783 (1998-06-01), Migdal et al.
patent: 5872902 (1999-02-01), Kuchkuda et al.
patent: 5877771 (1999-03-01), Drebin et al.
patent: 5987567 (1999-11-01), Rivard et al.
patent: 6104415 (2000-08-01), Gossett
patent: 6130680 (2000-10-01), Cox et al.
Williams, L. “Pyramidal Parametrics”,Computer Graphics, vol. 17, No. 3, Jul. 1983; pp. 1-11.
Chung Daniel J
Luu Matthew
Quarles & Brady LLP
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