Attribute blending system for composing computer-graphic images from objects
First Claim
1. In a computer graphics display apparatus including a frame buffer to drive a pixel display, a system to provide picture element (pixel) signals to said frame buffer for an anti-aliased display of polygons that are defined as located at various depths along a depth dimension in a pyramid of vision (model space), the pyramid of vision being defined by a view point having at least one ray associated with a pixel of said contending display, said ray passing through certain of said contending polygons at various points of said polygons, said contending polygons having attributes contending for said pixel, said display being defined in two dimensional space within said pyramid of vision, and further having a determined coarseness parameter indicated in the depth dimension, said system comprising:
- means for providing representative signals for each of, a forward contending polygon and a rearward contending polygon, in the depth dimension of model space, said forward contending polygon having a forward point along said ray in said depth dimension, said rearward contending polygon having a rearward point along said ray in said depth dimension;
means for determining representative signals for the distance in said depth dimension between said forward point and said rearward point in model space;
means for providing representative signals for said coarseness parameter in model space;
means for computing blended attribute pixel data signals, said blended attribute pixel data signals being a blended attribute of said forward and rearward polygons, by correlating said representative signals for said distance in said depth dimension between said forward and said rearward points with signals representative of said coarseness parameter; and
means for storing said blended attribute pixel data signals in said frame buffer for driving a computer graphics pixel display.
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Abstract
Objects contending for representation in pixels of a graphics display selectively are awarded a fractional area within a pixel on the basis of: coarse calculations in the Z dimension, aggregate demands of the objects and blending techniques free of binary position resolutions. Specifically, the area occupied by a polygon within a pixel is represented using a single number α, which may variously be defined, for example, a value of "0" indicates no area occupied within the pixel, while a value of "255" indicates full pixel coverage. Fine calculations in the Z dimension for binary resolutions are avoided by the blending techniques with attendant antialiasing. A chain of mixer units for storage and blending in pipeline processing compensate the non-associative characteristic of repeated blending.
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Citations
19 Claims
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1. In a computer graphics display apparatus including a frame buffer to drive a pixel display, a system to provide picture element (pixel) signals to said frame buffer for an anti-aliased display of polygons that are defined as located at various depths along a depth dimension in a pyramid of vision (model space), the pyramid of vision being defined by a view point having at least one ray associated with a pixel of said contending display, said ray passing through certain of said contending polygons at various points of said polygons, said contending polygons having attributes contending for said pixel, said display being defined in two dimensional space within said pyramid of vision, and further having a determined coarseness parameter indicated in the depth dimension, said system comprising:
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means for providing representative signals for each of, a forward contending polygon and a rearward contending polygon, in the depth dimension of model space, said forward contending polygon having a forward point along said ray in said depth dimension, said rearward contending polygon having a rearward point along said ray in said depth dimension; means for determining representative signals for the distance in said depth dimension between said forward point and said rearward point in model space; means for providing representative signals for said coarseness parameter in model space; means for computing blended attribute pixel data signals, said blended attribute pixel data signals being a blended attribute of said forward and rearward polygons, by correlating said representative signals for said distance in said depth dimension between said forward and said rearward points with signals representative of said coarseness parameter; and means for storing said blended attribute pixel data signals in said frame buffer for driving a computer graphics pixel display. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. function centered on said pixel for computing said blended attribute. 11. For use in conjunction with a computer graphics display apparatus including a frame buffer, a process for providing picture element (pixel) signals to the frame buffer for an anti-aliased display of polygons that are defined as located at various depths along a depth dimension in a pyramid of vision (model space), the pyramid of vision being defined by a view point having at least one ray associated with a pixel of said display, said ray passing through certain of said contending polygons at various points of said polygons, said contending polygons having attributes contending for said pixel, said display being defined in two dimensional space within said pyramid of vision, and further having a determined coarseness parameter indicated in the depth dimension, said process including the steps of:
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providing representative signals for each of, a forward contending polygon and a rearward contending polygon, in the depth dimension of model space, said forward contending polygon having a forward point along said ray in said depth dimension, said rearward contending polygon having a rearward point along said ray in said depth dimension; determining representative signals for the distance in said depth dimension between said forward point and said rearward point in model space; providing representative signals for said coarseness parameter in model space; computing blended attribute pixel data signals, said blended attribute pixel data being a blended attribute between said forward and rearward polygons, by correlating said representative signals for the distance in said depth dimension between said forward and said rearward points with signals representative of said coarseness parameter; and storing said blended attribute pixel data signals in said frame buffer for
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- 11. driving a computer graphics display. 12. A computer graphics process according to claim 11 wherein said contending polygons have attributes to represent color and said computing step computes a blended attribute of
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16. distance. 17. A computer graphics process according to claim 16 wherein said correlated distance R is defined in accordance with the equation:
- ##EQU2## where ZB represents position of said rearward point along said ray in said depth dimension, ZA represents position of said forward point
- View Dependent Claims (17, 18)
Specification
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- Resources
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Current AssigneeEvans & Sutherland Computer Corp. (Elevate Entertainment, Inc.)
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Original AssigneeEvans & Sutherland Computer Corp. (Elevate Entertainment, Inc.)
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InventorsWatkins, Gary S.
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Primary Examiner(s)Zimmerman, Mark K.
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Application NumberUS08/310,583Time in Patent Office502 DaysField of Search395/121, 395/122, 395/126, 395/131, 395/132, 395/129, 345/150, 345/149US Class Current345/422CPC Class CodesG06T 15/503 Blending, e.g. for anti-ali...
