Texture mapping circuit for performing data interpolations

• US 5,943,058 A
• Filed: 01/25/1996
• Issued: 08/24/1999
• Est. Priority Date: 01/25/1996
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Silicon Graphics Incorporated (Graphics Properties Holdings, Inc.)
• Inventors: Nagy, Michael B.
• Primary Examiner(s): Vo, Cliff N.
• Application Number:
  US08/591,892
• Time in Patent Office: 1,307 Days
• Field of Search: 345/419, 345/420, 345/421, 345/430, 345/431
• US Class Current: 345/582
• CPC Class Codes: G06T 15/04 Texture mapping

Abstract

A method and apparatus for producing output values corresponding to pixels of an input image. A coordinate translation circuit for is provided for performing coordinate translation from input pixel color components to corresponding texture coordinates. The texture coordinates collectively determine a texture address. The coordinate translation circuit also generates a set of interpolation factors in one embodiment used to resample around the point in texture space defined by the texture address. An interpolation circuit is coupled to the coordinate translation circuit to receive the texture address and the set of interpolation factors. The interpolation circuit uses the texture address and the set of interpolation factors to produce an output value. Typically, the output value represents a multidimensional lookup of the color components interpolated into multidimensional space. An application of the method and device of the invention includes a color conversion method for converting input pixel color components from a source color space to a destination color space.

Claims

1. An apparatus for use in a graphics system, said apparatus producing output values corresponding to input pixels, each input pixel having n color components, where n is >

=1, each output value representing the result of an n-dimensional lookup of said color components, said apparatus comprising;

a bus which provides said color components;

a coordinate translation circuit coupled to said bus for receiving said color components, said coordinate translation circuit configured to perform coordinate translation from said color components to corresponding texture coordinates that collectively determine a texture address; and

a texture map memory coupled to said coordinate translation circuit, said texture map memory having stored therein a lookup table (LUT).

2. The apparatus of claim 1, wherein said texture address is used to index into said LUT, wherein said coordinate translation circuit also generates a set of interpolation factors, and further comprising an interpolation circuit coupled to said coordinate translation circuit, said interpolation circuit performing interpolation using said texture address and said set of interpolation factors to produce said output values.

3. The apparatus of claim 2, wherein one or more of said color components are scaled and biased prior to being received by said coordinate translation circuit.

4. The apparatus of claim 2, wherein said texture address defines one or more interpolation solids, said interpolation is a trilinear interpolation and said trilinear interpolation takes place within one of said interpolation solids.

5. The apparatus of claim 2, wherein said color components include a first color component comprising a predetermined number of upper bits corresponding to the size of a corresponding dimension of said LUT and a number of remaining lower bits, wherein said texture coordinates include a first texture coordinate comprising an integer portion, said coordinate translation circuit configured to select said predetermined number of upper bits from said first color component for said integer portion of said first texture coordinate, said coordinate translation circuit further configured to select said number of remaining lower bits for use as one of said set of interpolation factors.

6. The apparatus of claim 3, wherein said color components are scaled and biased using the following equation:

##EQU2## wherein C_input represents one of said color components, TEXCOORD represents the resulting texture coordinate corresponding to C_input, size is the size of the corresponding dimension of said LUT as stored in the texture memory, m is the number of said remaining lower bits of C_input.

7. A texture mapping circuit for use in a graphics system, said texture mapping circuit transforming input pixel data into a corresponding texture address, said texture address used for addressing a lookup table (LUT), said texture mapping circuit comprising:

a data to texture coordinate translator for receiving said input pixel data, said data to texture coordinate translator configured to transform said input pixel data to said corresponding texture address; and

a texture memory coupled to said data to texture coordinate translator, said texture memory having stored therein said LUT.

8. The texture mapping circuit of claim 7, wherein said texture address is determined by a set of texture coordinates, each of said texture coordinates includes an integer portion and a fractional part, said data to texture coordinate translator further comprising:

a texture coordinate translation circuit configured to generate said integer portions and said fractional parts, said integer portions collectively determining said texture address, said texture address defining a point in said texture memory for determining a texture volume containing a portion of said LUT, said fractional parts collectively representing a set of interpolation factors.

9. The texture mapping circuit of claim 8, wherein said texture mapping circuit further comprises:

an alpha bit selection circuit for receiving a portion of said input pixel data, said alpha bit selection circuit configured to produce an alpha output; and

an interpolation circuit coupled to said data to texture coordinate translator, said interpolation circuit using said texture address and said interpolation factors to generate interpolated output values from said portion of said LUT, wherein said texture mapping circuit can be configured to substitute said alpha output for a corresponding interpolated output value of said interpolation circuit.

10. A method, for use with a texture mapping circuit, for producing output values corresponding to pixels of an input image, each pixel having n components, said texture mapping circuit comprising a coordinate translation circuit coupled to a bus, and an interpolation circuit coupled to said coordinate translation circuit and said bus, said method comprising the steps of:

said coordinate translation circuit receiving said components;

said coordinate translation circuit converting said components to a texture address and a set of interpolation factors; and

said interpolation circuit interpolating values retrieved from a texture memory to produce said output values.

11. The method of claim 10, wherein said texture address is used to index into a lookup table (LUT) stored in said texture memory, and said LUT having dimensions corresponding to said components.

12. The method of claim 11, said method further comprising the steps of scaling and biasing one or more of said components that are used as texture coordinates prior to said step of converting said components to a texture address and a set of interpolation factors.

13. The method of claim 11, wherein said texture address defines one or more interpolation solids within said texture memory, and said step of interpolating values retrieved from a texture memory is accomplished by performing trilinear interpolation within one of said interpolation solids.

14. The method of claim 11, wherein each of said components comprises a number of upper bits and a number of remaining lower bits, wherein said step of converting said components further comprises the steps of:

selecting said number of upper bits from each of said components, said number of upper bits corresponding to the size of the corresponding dimension of said LUT, said number of upper bits representing one of said texture coordinates; and

selecting said number of remaining lower bits from each of said components, said number of remaining lower bits representing one of said set of interpolation factors.

15. A color conversion method, for use with a texture mapping circuit, for converting input pixel color components from a source color space to a destination color space, said color conversion method producing an output value in said destination color space representing the result of a multidimensional lookup of said input pixel color components interpolated into multidimensional space, said texture mapping circuit comprising a coordinate translation circuit coupled to a bus, and a texture map memory, said method comprising the steps of:

receiving said input pixel color components from an input image;

translating said input pixel color components into texture coordinates that define an address in said texture map memory; and

retrieving one or more values from said texture map memory to produce said output value.

16. The color conversion method of claim 15, wherein said source color space is RGB and said destination color space comprises one of CMY, CMYK, HSV, LUV, LHS, LAB, or YUV.

17. The color conversion method of claim 15, wherein said source color space comprises one of CMY, CMYK, HSV, LUV, LHS, LAB, or YUV and said destination color space is RGB.

18. The color conversion method of claim 15, wherein said texture map memory has stored therein a lookup table (LUT), said LUT contains values from said destination color space, and said address is used to index into said LUT.

19. The color conversion method of claim 18 wherein:

said LUT has a dimension corresponding to each of said input pixel color components, each of said texture coordinates comprises an integer portion and a fractional part, and said step of translating includes selecting a predetermined number of bits from said input pixel color components for said integer portion and using a remaining number of bits from said input pixel color components for said fractional part, said predetermined number of bits based upon the size of the corresponding dimension of said LUT.

20. The color conversion method of claim 19 wherein:

said step of translating includes performing scaling and biasing using the following equation;

##EQU3## wherein C_input represents one of said input pixel color components, TEXCOORD represents the resulting texture coordinate corresponding to C_input, size is the size of the dimension of the LUT corresponding to the input pixel color component, C_input, and n is the number of said remaining lower bits of C_input.

21. The color conversion method of claim 19 wherein said texture mapping circuit further comprises an interpolation circuit coupled to said coordinate translation circuit and said step of retrieving further comprises the steps of:

said interpolation circuit selecting a texture volume within said texture memory using said address, said address defined by the integer portions of said texture coordinates;

said interpolation circuit determining an interpolation point using said address and the fractional portions of said texture coordinates; and

said interpolation circuit resampling around said interpolation point within said texture volume.

22. The color conversion method of claim 21 wherein

said texture volume is a 2×

2×

2 cube and said address defines the lower, left, front location of said texture volume; and

said step of resampling includes performing trilinear interpolation using the interpolation point and eight points within said texture volume.

23. A method of producing special effects, for use with texture mapping circuit, converting an original image stored in a texture map memory to a modified output image using input pixel components containing displacements, said method of producing special effects generating an output value determined from said original image and said displacements, said output value representing the result of a multidimensional lookup of said displacements interpolated into multidimensional space, said texture mapping circuit comprising a coordinate translation circuit coupled to a bus, and said texture map memory, said method comprising the steps of:

receiving said displacements from an input image;

translating said displacements into texture coordinates that define an address in said texture map memory; and

retrieving one or more values from said texture map memory to produce said output value.

24. The method of claim 23, wherein said texture map memory has stored therein a lookup table (LUT), said LUT contains said original image, and said texture coordinates are used to index into said LUT.

25. The method of claim 24 wherein:

said LUT has a dimension corresponding to each of said displacements, each of said texture coordinates comprises an integer portion and a fractional part, and said step of translating includes selecting a predetermined number of bits from said displacements for said integer portion and using a remaining number of bits from said displacements for said fractional part, said predetermined number of bits based upon the size of the corresponding dimension of said LUT.

26. The method of claim 25 wherein prior to said step of translating said displacements are scaled and biased.

27. The method of claim 25 wherein said texture mapping circuit further includes an interpolation circuit coupled to said coordinate translation circuit and said step of retrieving further comprises the steps of:

said interpolation circuit selecting a texture volume within said texture map memory using said address, said address defined by the integer portions of said texture coordinates;

said interpolation circuit determining an interpolation point using said address and the fractional portions of said texture coordinates; and

said interpolation circuit resampling around said interpolation point within said texture volume.

28. A method for following data contours in multi-dimensional space, for use with a texture mapping circuit, mapping input texture coordinates to the surface of a target image stored in a texture map memory, said method producing an output value representing the result of a multidimensional lookup of said input texture coordinate interpolated onto the surface of said target image, said texture mapping circuit comprising a coordinate translation circuit coupled to a bus, and said texture map memory, said method comprising the steps of:

receiving said input texture coordinates from an input image;

translating said input texture coordinates into texture coordinates that define an address in said texture map memory; and

retrieving one or more values from said texture map memory to produce said output value.

29. The method of claim 28, wherein said texture map memory has stored therein a lookup table (LUT), said LUT contains data that includes the surface to be scanned, and said texture coordinates are used to index into said LUT.

30. The method of claim 29 wherein:

said LUT has a dimension corresponding to each of said input texture coordinates, each of said texture coordinates comprises an integer portion and a fractional part, and said step of translating includes selecting a predetermined number of bits from said input texture coordinates for said integer portion and using a remaining number of bits from said input texture coordinates for said fractional part, said predetermined number of bits based upon the size of the corresponding dimension of said LUT.

31. The method of claim 30 wherein prior to said step of translating said input texture coordinates are scaled and biased.

32. The method of claim 30 wherein said texture mapping circuit further includes an interpolation circuit coupled to said coordinate translation circuit and said step of retrieving further comprises the steps of:

said interpolation circuit selecting a texture volume within said texture map memory using said address, said address defined by the integer portions of said texture coordinates;

said interpolation circuit determining an interpolation point using said address and the fractional portions of said texture coordinates; and

said interpolation circuit resampling around said interpolation point within said texture volume.

33. A computer system comprising:

a bus;

a processor coupled to said bus;

a first memory coupled to said bus having stored therein input pixel data, said input pixel data including color components;

a second memory coupled to said bus addressed in a multi-dimensional fashion having stored therein a lookup table (LUT);

a translation means, coupled to said bus, for translating said color components into an address and interpolation factors;

means, coupled to said second memory, for determining an interpolation solid in said second memory containing said address; and

an interpolation means, coupled to said translation means, for performing linear interpolation within said interpolation solid using said interpolation factors, said linear interpolation resulting in an output value representing a multidimensional lookup in said LUT of one of said input pixel'"'"'s color components.

34. The computer system of claim 33, wherein said first memory is a main memory and said second memory is a texture memory.

35. The computer system of claim 34, wherein said translation means separates each of said color components into an integer component and a fractional component, said integer components represent said address and are used for integer addressing said LUT and said fractional components represent said interpolation factors.

36. The computer system of claim 35, wherein each of said integer components has a variable number of bits depending upon the size of the corresponding dimension of said LUT.

37. The computer system of claim 36, wherein those of said color components that contribute to said address are scaled and biased prior to being translated by said translation means.

38. The computer system of claim 37, wherein said scaling and biasing are performed by multiplying each integer component by a scaling factor and adding a bias, wherein said scaling factor is ##EQU4## said bias is 2^n-1 +0.5, size is the size of the corresponding dimension of the LUT as stored in the texture memory, and n is the number of bits used to represent the corresponding fractional component.

39. A translation circuit configured to translate one or more pixel color components to corresponding texture coordinates for addressing a texture map memory.

40. A method of accessing a texture map memory comprising the steps of:

receiving input pixel color components;

translating the input pixel color components into texture coordinates; and

retrieving one or more values from a texture map memory by addressing the texture map memory with the texture coordinates.