Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
94 words
A method of calculating at least one texture map gradient (∇S) at each display point to be displayed on a display device, comprising the steps of: providing polygon vertex data for each vertex of an input polygon to be displayed, said polygon vertex data including at least one texture value for display points corresponding to each vertex (10, 12); and calculating directly from said at least one texture value of respective vertices of a particular input polygon said at least one texture map gradient for each display point of said particular input polygon (14).
Claim 2
Independent Claim
94 words
An apparatus for calculating at least one texture map gradient at each display point to be displayed on a display device, comprising: means for providing polygon vertex data (10, 12) for each vertex of an input polygon to be displayed, said polygon vertex data including at least one texture value for display points corresponding to each vertex; and means for calculating (14) directly from said at least one texture value of respective vertices of a particular input polygon said at least one texture map gradient for each display point of said particular input polygon.
Claim 3
Dependent Claim
36 words
An apparatus as in claim 2, wherein said at least one texture map gradient is calculated at each pixel using data received once per polygon for an input image represented by a plurality of said polygons.
Claim 4
Dependent Claim
20 words
An apparatus as in claim 2, further comprising means for interpolating said at least one texture value in perspective space.
Claim 5
Dependent Claim
156 words
An apparatus as in claim 2, wherein said at least one texture map gradient ∇G is calculated by said calculating means (14) for each display point in display space using a value of texture coordinate G at each display point in accordance with the equation: |∇G| = l W * (K₁² + (K₂(G-G₀))²) ½ where: W is an interpolated perspective value of the display point having texture coordinate G; G₀ is a texture coordinate value of a point where a vector normal to a plane of the input polygon intersects a viewpoint of the input polygon in world space; K₁ = W*h, where h is a vector parallel to a W contour line in which W has a constant value over the input polygon; and K₂ = K₁/(G₁-G₀), where G₁ is a texture coordinate value where the slope of a G contour line in which G has a constant value over the input polygon is one.
Claim 6
Dependent Claim
144 words
An apparatus as in claim 5, wherein said calculating means comprises: means (12) for determining G₀, log₂ (K₁) and log₂ (K₂) once per polygon; means for determining, by perspective interpolation, a value of G for a display point of the input polygon using values of G at vertices of the input polygon; means (30-42) for determining log₂ |G-G₀|; means for determining a value of W for the display point of the input polygon by linear interpolation; means (46-52) for determining log₂(l/W); means (54, 56) for selectively adding log₂(G-G₀), log₂(l/W), log₂(K₁) and log₂(K₂) to get a first sum log₂(K₂(s-s₀)/W) and a second sum log₂(K₁/W); means for limiting (58, 60) said first and second sums to a predetermined range of integer values; and means for selecting (62, 64) the greater of said first sum and said second sum as said at least one texture map gradient.
Claim 7
Dependent Claim
28 words
An apparatus as in claim 6, wherein said calculation performed by said calculating means is repeated for each coordinate direction represented by said at least one texture value.
Claim 8
Dependent Claim
118 words
An apparatus as in claim 6, wherein said means for determining log₂(G-G₀) (30-42) and log₂(l/W) (46-52) respectively comprise a fixed to float normalizer (40, 48) for converting an input value into a binary number in the form of exponent.mantissa and an adder (42, 50) for adding a binary one to the fourth fractional bit of the mantissa of said binary number, where the mantissa is determined by shifting the binary input value to the left until a one is to the left of the decimal point, discarding the one to the left of the decimal point to leave the fractional part as said mantissa, and determining a binary representation of the number of said shifts as said exponent.