Determining the level of detail for texture mapping in computer graphics

Claim 3

The method of claim 1 further comprising: obtaining signals S2 representing derivatives of the texture coordinates with respect to another screen coordinate; and providing the signals S2 to the circuit to obtain the LOD.

Claim 4

The method of claim 1 wherein the LUT stores values representing (1/2)log 2 (X 2 +Y 2 ) for pairs (X,Y), such that for all the values in the LUT, 0≦Y≦X.

Claim 5

The method of claim 3 wherein when the circuit uses the LUT to generate the LOD, the circuit performs as follows: the circuit determines the values α and β such that α represents the maximum of the absolute values represented by signals S1 at inputs of the circuit and β represents the minimum of said absolute values; the circuit provides values α and β to the LUT; the circuit generates the LOD from the LUT output.

Claim 6

The method of claim 4 wherein for all the values in the LUT, X is in a predetermined interval, and α is in said predetermined interval, and β is such that 0≦β≦α.

Claim 7

The method of claim 5 wherein for all the values in the LUT, 1≦X≦2.

Claim 8

The method of claim 1 wherein: FN(-X,Y)=FN(X,Y); FN(X,-Y)=FN(X,Y); and FN(X,Y)=FN(Y,X).

Claim 9

The method of claim 1 wherein the LUT stores only values of the function FN for X in a predetermined interval, and when X is out of said predetermined interval the circuit calculates FN(X, Y) as FN(X/F, Y/F)+k(F) where F is such that X/F is in said predetermined interval, the value FN(X/F, Y/F) being provided by the LUT.

Claim 10

The method of claim 1 wherein FN(X,Y)=A*log.sub.2 (X.sup.2 +Y.sup.2) where A is a predetermined constant.

Claim 11

The method of claim 9 wherein the LUT stores only values of the function FN for X in a predetermined interval, and when X is out of said predetermined interval the circuit calculates FN(X, Y) as FN(X/F, Y/F)+k(F) where F is such that X/F is in said predetermined interval, the value FN(X/F, Y/F) being provided by the LUT.

Claim 14

The method of claim 11 further comprising: obtaining signals representing ∂u/∂y and ∂v/∂y where y is a screen coordinate of image points; and providing signals representing ∂u/∂y and ∂v/∂y to the circuit to obtain the LOD.

Claim 15

The method of claim 11 wherein the LUT stores values representing (1/2)log 2 (X 2 +Y 2 ) for pairs (X,Y), such that for all the values in the LUT, 0≦Y≦X.

Claim 16

The method of claim 13 wherein when the circuit uses the LUT to generate the LOD, the circuit performs as follows: the circuit determines the absolute values of ∂u/∂x and ∂v/∂x, and determines the values X1 and Y1 such that X1 is the maximum of the absolute values of ∂u/∂x and ∂v/∂x and Y1 is the minimum of the absolute values of ∂u/∂x and ∂v/∂x; the circuit generates a first signal from the value X1 and a second signal from the value Y1, and the circuit provides the first and second signals as respective inputs X and Y to the LUT; the circuit generates the LOD from the LUT output.

Claim 17

The method of claim 14 wherein for all the values in the LUT, X belongs to a predetermined interval, and the first signal represents a value XX1 which is in the predetermined interval, and the second signal represents the value YY1 such that 0≦YY1≦XX1.

Claim 18

The method of claim 15 wherein for all the values in the LUT, 1≦X≦2.

Claim 19

The method of claim 11 wherein: FN(-X,Y)=FN(X,Y); FN(X,-Y)=FN(X,Y); and FN(X,Y)=FN(Y,X).

Claim 20

The method of claim 11 wherein the LUT stores only values of the function FN for X in a predetermined interval, and when X is out of said predetermined interval the circuit calculates FN(X, Y) as FN(X/F, Y/F)+k(F) where F is such that X/F is in said predetermined interval, the value FN(X/F, Y/F) being provided by the LUT.

Claim 21

The method of claim 11 wherein FN(X, Y)=A * log 2 (X 2 +Y 2 ) where A is a predetermined constant.

Claim 22

The method of claim 19 wherein the LUT stores only values of the function FN for X in a predetermined interval, and when X is out of said predetermined interval the circuit calculates FN(X, Y) as FN(X/F, Y/F)+k(F) where F is such that X/F is in said predetermined interval, the value FN(X/F, Y/F) being provided by the LUT.

Claim 23

A circuit for determining a level of detail (LOD) to perform texture mapping to create an image by a computer, the circuit comprising a look-up table (LUT) for storing values of a predetermined function FN of at least two variables X and Y such that, for any positive constant F, FN(X/F,Y/F)=FN(X,Y)+k(F) where k(F) is a function of F but not of X and Y, the circuit being for receiving signals S1 representing derivatives of texture coordinates (u,v) with respect to a first screen coordinate and using the LUT to generate a function of the derivatives, the circuit having an output for providing the LOD which is a function of the derivatives.

Claim 24

A circuit for determining a level of detail (LOD) to perform texture mapping to create an image by a computer, the circuit comprising a look-up table (LUT) for storing values of a predetermined function FN of at least two variables X and Y such that, for any positive constant F, FN(X/F,Y/F)=FN(X,Y)+k(F) where k(F) is a function of F but not of X and Y, the circuit being for receiving signals S1 representing derivatives of texture coordinates (u,v) with respect to a first screen coordinate and using the LUT to generate a function of the derivatives, the circuit having an output for providing the LOD which is a function of the derivatives.

Claim 25

The circuit of claim 21 wherein the circuit is also for receiving a signal S2 representing derivatives of the texture coordinates with respect to a second screen coordinate and for using the LUT to generate a function of the derivatives with respect to the second screen coordinate, the LOD being a function of the derivatives with respect to the first and the second coordinates.

Claim 26

The circuit of claim 21 wherein the LUT stores values representing (1/2)log 2 (X 2 +Y 2 ) for pairs (X,Y), such that for all the values in the LUT, 0≦Y≦X.

Claim 27

The circuit of claim 23 wherein when the circuit uses the LUT to generate the LOD, the circuit performs as follows: the circuit determines the values α and β such that α represents the maximum of the absolute values represented by signals S1 at inputs of the circuit and β represents the minimum of said absolute values; the circuit provides values αand β to the LUT; the circuit generates the LOD from the LUT output.

Claim 28

The circuit of claim 24 wherein for all the values in the LUT, X is in a predetermined interval, and α is in said predetermined interval, and β is such that 0≦β≦α.

Claim 29

The circuit of claim 25 wherein for all the values in the LUT, 1≦X≦2.

Claim 30

The circuit of claim 21 wherein: FN(-X,Y)=FN(X,Y); FN(X,-Y)=FN(X,Y); and FN(X,Y)=FN(Y,X).

Claim 31

The circuit of claim 21 wherein the LUT stores only values of the function FN for X in a predetermined interval, and when X is out of said predetermined interval the circuit calculates FN(X, Y) as FN(X/F, Y/F)+k(F) where F is such that X/F is in said predetermined interval, the value FN(X/F, Y/F) being provided by the LUT.

Claim 32

The circuit of claim 21 wherein FN(X, Y)=A * log 2 (X 2 +Y 2 ) where A is a predetermined constant.

Claim 33

The circuit of claim 29 wherein the LUT stores only values of the function FN for X in a predetermined interval, and when X is out of said predetermined interval the circuit calculates FN(X, Y) as FN(X/F, Y/F)+k(F) where F is such that X/F is in said predetermined interval, the value FN(X/F, Y/F) being provided by the LUT.

Claim 34

The circuit of claim 30 wherein the LUT stores only values of the function FN for Y≦X, and the circuit performs as follows: the circuit determines the absolute values of the derivatives ∂u/∂x and ∂v/∂x of the respective texture coordinates (u, v) with respect to the screen coordinate x which is said first screen coordinate, and the circuit determines the values X1 and Y1 such that X1 is the maximum of the absolute values of ∂u/∂x and ∂v/∂x and Y1 is the minimum of the absolute values of ∂u/∂x and ∂v/∂x; the circuit provides the values X1/F1 and Y1/F1 as respective inputs X and Y to the LUT, where F1 is such that X1/F1 is in said predetermined interval, and the circuit obtains from the LUT the value A * log 2 ((X1/F1) 2 +(Y1/F1) 2 ) and uses this value to determine a value B * log 2 ((∂u/∂x) 2 +(∂v/∂x) 2 ) where B is a predetermined constant; the circuit determines the absolute values of derivatives ∂u/∂y and ∂v/∂y of the respective texture coordinates (u, v) with respect to another screen coordinate y, and determines the values X2 and Y2 such that X2 is the maximum of the absolute values of ∂u/∂y and ∂v/∂y and Y2 is the minimum of the absolute values of ∂u/∂y and ∂v/∂y; the circuit provides the values X2/F2 and Y2/F2 as respective inputs X and Y to the LUT, where F2 is such that X2/F2 is in said predetermined interval, and the circuit obtains from the LUT the value A * log 2 ((X2/F2) 2 +(Y2/F2) 2 ) and uses this value to determine B * log 2 ((∂u/∂y) 2 +(∂v/∂y) 2 ); the circuit generates the LOD from the values B * log 2 ((∂u/∂x) 2 +(∂v/∂x) 2 ) and B * log 2 ((∂u/∂y) 2 +(∂v/∂y) 2 ).

Claim 35

The circuit of claim 31 wherein B=1/2, and the circuit generates the LOD as the maximum of the values B * log 2 ((∂u/∂x) 2 +(∂v/∂x) 2 ) and B * log 2 ((∂u/∂y) 2 +(∂v/∂y) 2 ).

Claim 36

The circuit of claim 31 wherein A=B=1/2.