EP0718797A2
Expired / Lapsed
EP
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Perspective correction of texture in graphics by adaptive approximation
Assignee: Sun Microsystems Inc
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Filing: 1995-12-19
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Granted: —
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Expires: 2015-12-19
Abstract
Abstract The present invention provides a computer graphics system with a texel value generator capably of generating texel values using a minimal amount of computationally intensive divisions while maintaining a selectable texel accuracy criteria along a scan line. This is accomplished by adaptively selecting divisional points which delineate the scan line segments along each scan line such that the divisional points are as widely spaced as possible without exceeding the selected texel accuracy criteria. Having selected the texel accuracy criteria, such as a texel error bound optimally spaced, divisional points along the scan lines are selected as a function of the selected accuracy criteria. In general, since texture gradients are not evenly distributed over the surface of a given object and texture variations are present between different objects of the image, it is advantageous to adaptively select division points one at a time, skipping as many pixels in between divisional points as the local texture gradient will allow. Accurate texel values are computed at these divisional points and also at the end points of the scan line. Approximate texel values are then computed for the pixels located between adjacent pair of divisional points along the scan line using a suitable scheme such as linear interpolation.
Inventors
- 👤 Walter E. Donovan
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 04:37
CPC Classifications
G; G06; G06T; G06T15/00; G06T15/04
Claims Analysis
Total Claims: 38
Claim 1
Independent Claim
103 words
In a computer graphics system for generating and displaying images of objects on a display device, the images including pixels having pixel values, the graphics system including elements for modifying the images displayed on the display device, a method for efficiently computing texel values so as to display texture on a given object from a given perspective, said method comprising the steps of: adaptively selecting a plurality of divisional points between a pair of end points along a scan line; and approximating a plurality of intermediate texel values for a corresponding plurality of pixels located between adjacent divisional points of said scan line.
Claim 2
Dependent Claim
13 words
The method of claim 1 wherein said approximating step includes an interpolating step.
Claim 3
Dependent Claim
14 words
The method of claim 2 wherein said interpolating step is a linear interpolating step.
Claim 4
Dependent Claim
41 words
The method of claim 1 wherein said adaptive selection step comprises the steps of: selecting a texel accuracy criteria; and computing the locations of said divisional points located along said scan line as a function of said selected texel accuracy criteria.
Claim 5
Dependent Claim
15 words
The method of claim 4 wherein said texel accuracy criteria is a texel error bound.
Claim 6
Dependent Claim
38 words
The method of claim 5 wherein said texel error bound is a constant e , and a step t between adjacent divisional points is computed using an equation: t = e + 2 e wl | dw |
Claim 7
Dependent Claim
41 words
The method of claim 1 further comprising the steps of: approximating a second plurality of intermediate texel values for a second corresponding plurality of pixels located between one of said end points and an adjacent divisional point of said scan line.
Claim 8
Dependent Claim
13 words
The method of claim 7 wherein said approximating step includes an interpolating step.
Claim 9
Dependent Claim
14 words
The method of claim 8 wherein said interpolating step is a linear interpolating step.
Claim 10
Dependent Claim
30 words
The method of claim 1 further comprising the step of: accurately computing a corresponding plurality of texel values at said divisional points and said end points of said scan line.
Claim 11
Dependent Claim
23 words
The method of claim 1 further comprising the step of using said intermediate texel values to modify said pixel values of said pixels.
Claim 12
Dependent Claim
42 words
The method of claim 11 wherein said modifications of said pixel values includes a step of computing MIP map level values for said intermediate texel values using an equation: level = 1 2 log 2 du dx 2 + dv dx 2
Claim 13
Independent Claim
73 words
A method of providing a texel generator for efficiently computing texel values so as to display texture on a given object from a given perspective, said method comprising the steps of: providing a calculator for adaptively selecting a plurality of divisional points along a scan line; and providing an approximator for approximating a plurality of intermediate texel values for a corresponding plurality of pixels located between adjacent divisional points of said scan line.
Claim 14
Dependent Claim
11 words
The method of claim 13 wherein said approximator includes an interpolator.
Claim 15
Dependent Claim
12 words
The method of claim 14 wherein said interpolator is a linear interpolator.
Claim 16
Dependent Claim
43 words
The method of claim 13 wherein said calculator includes an element for performing the steps of: selecting a texel accuracy criteria; and computing the locations of said divisional points located along said scan line as a function of said selected texel accuracy criteria.
Claim 17
Dependent Claim
15 words
The method of claim 16 wherein said texel accuracy criteria is a texel error bound.
Claim 18
Dependent Claim
38 words
The method of claim 17 wherein said texel error bound is a constant e , and a step t between adjacent divisional points is computed using an equation: t = e + 2 e wl | dw |
Claim 19
Dependent Claim
38 words
The method of claim 13 wherein said approximator also approximates a second plurality of intermediate texel values for a second corresponding plurality of pixels located between an end point and an adjacent divisional point of said scan line.
Claim 20
Dependent Claim
30 words
The method of claim 13 wherein said calculator includes an element for accurately computing a plurality of texel values at said divisional points said end points of said scan line.
Claim 21
Dependent Claim
27 words
The method of claim 13 further comprising the step of providing a combiner for using said intermediate texel values to modify said pixel values of said pixels.
Claim 22
Dependent Claim
42 words
The method of claim 21 wherein said modification of said pixel values includes a step of computing MIP map level values for said intermediate texel values using an equation: level = 1 2 log 2 du dx 2 + dv dx 2
Claim 23
Dependent Claim
94 words
An adaptive texel value generator useful in association with a computer graphics system for generating, modifying and displaying an image of objects on a display device, the image including pixels having pixel values, said texel value generator comprising: a calculator for adaptively computing the locations of a plurality of divisional points along a scan line as a function of a selected texel accuracy criteria; and an approximator coupled to said calculator, for computing a plurality of intermediate texel values for a corresponding plurality of pixels located between adjacent divisional points of said scan line.
Claim 24
Dependent Claim
21 words
The generator of claim 23 further comprising a memory element coupled to said calculator, for storing said selected texel accuracy criteria.
Claim 25
Dependent Claim
16 words
The generator of claim 24 wherein said stored texel accuracy criteria is a texel error bound.
Claim 26
Dependent Claim
38 words
The generator of claim 25 wherein said texel error bound is a constant e , and a step t between adjacent divisional points is computed using an equation: t = e + 2 e wl | dw |
Claim 27
Dependent Claim
21 words
The generator of claim 23 wherein said approximator includes an interpolator for interpolaring between texel values of said adjacent divisional points.
Claim 28
Dependent Claim
12 words
The generator of claim 25 wherein said interpolator is a linear interpolator.
Claim 29
Dependent Claim
20 words
The generator of claim 23 wherein said calculator includes a divider for accurately computing texel values for said divisional points.
Claim 30
Dependent Claim
37 words
The generator of claim 23 wherein said pixel values are modified by computing MIP map levels of said intermediate texel values using an equation: level = 1 2 log 2 du dx 2 + dv dx 2
Claim 31
Dependent Claim
108 words
A texture mapping system useful in association with a computer graphics system for generating, modifying and displaying an image of objects on a display device, the image including pixels having pixel values, said graphics system comprising: a calculator for adaptively computing the locations of a plurality of divisional points along a scan line as a function of a selected texel accuracy criteria; an approximator coupled to said calculator, for computing a plurality of intermediate texel values for a corresponding plurality of pixels located between adjacent divisional points of said scan line; and a combiner coupled to said approximator for modifying said pixel values with said intermediate texel values.
Claim 32
Dependent Claim
22 words
The mapping system of claim 31 further comprising a memory element coupled to said calculator, for storing said selected texel accuracy criteria.
Claim 33
Dependent Claim
17 words
The mapping system of claim 32 wherein said stored texel accuracy criteria is a texel error bound.
Claim 34
Dependent Claim
39 words
The mapping system of claim 33 wherein said texel error bound is a constant e , and a step t between adjacent divisional points is computed using an equation: t = e + 2 e wl | dw |
Claim 35
Dependent Claim
22 words
The mapping system of claim 31 wherein said approximator includes an interpolator for interpolating between texel values of said adjacent divisional points.
Claim 36
Dependent Claim
13 words
The mapping system of claim 35 wherein said interpolator is a linear interpolator.
Claim 37
Dependent Claim
21 words
The mapping system of claim 31 wherein said calculator includes a divider for accurately computing texel values for said divisional points.
Claim 38
Dependent Claim
38 words
The mapping system of claim 31 wherein said pixel values are modified by computing MIP map levels of said intermediate texel values using an equation: level = 1 2 log 2 du dx 2 + dv dx 2
References Cited (Backward Citations)
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