Method and apparatus for rendering a two dimensional image from three dimensional image data

• US 6,243,488 B1
• Filed: 12/03/1996
• Issued: 06/05/2001
• Est. Priority Date: 08/05/1993
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Penna, David E.
• Primary Examiner(s): Couso, Yon
• Assistant Examiner(s): PATEL, JAYANTI K
• Application Number:
  US08/760,123
• Time in Patent Office: 1,645 Days
• Field of Search: 382/154, 382/285, 395/119, 395/125, 395/122, 395/124, 356/12, 345/139
• US Class Current: 382/154
• CPC Class Codes: G06T 15/04 Texture mapping

Abstract

Texture mapping or video mapping is performed in such a way as to obtain perspectively correct images, while at the same time not requiring excessive computational overheads. Non-linear functions required to achieve perspectively correct images are stored in the form of look-up tables. Depth extents at the extremes of a locus of interpolation are compared and from this comparison a particular look-up table, or a pair of look-up tables, are selected. When a pair of look-up tables are selected, it is possible to linearly interpolate between the two, in order to obtain a closer approximation to the desired non-linear response.

Claims

1. An image processing method for rendering a two dimensional output image comprised of pixels from three dimensional image data, wherein a random polyhedron is projected from a location of viewing as a two dimensional polygon having a boundary enclosing an area and defined in three dimensional space and pixel images from a two dimensional input image are mapped onto pixels within said projected two dimensional polygon, comprising the steps of:

providing a plurality of look-up tables each with a set of perspective correction factors corresponding to a location of viewing;

identifying at least two boundary points on said boundary of said polygon;

mapping pixels within said two dimensional input image corresponding to each of said at least two points on said polygon boundary according to a defined mapping function;

identifying a locus of pixels within said polygon extending between said at least two boundary points; and

mapping pixels within said two dimensional input image to each of said pixels of said locus of pixels within said polygon by (i) linearly interpolating at least one coordinate of each pixel along said locus of pixels to obtain an interpolated coordinate, (ii) identifying the look-up table corresponding to the location of viewing from which said two dimensional polygon was projected;

(iii) applying a correction factor from the set of correction factors in the selected lookup table to the interpolated coordinate to obtain a corrected coordinate for the pixel to be mapped from the two dimensional input image.

2. A method according to claim 1, wherein a plurality of look-up tables are provided and a required look-up table is selected by processing depth values.

3. A method according to claim 2, wherein two look-up tables are selected and new values for performing the look-up operation are determined by a process of linear interpolation.

4. A method according to claim 2, wherein a first depth value associated with a first position is divided by a second depth value associated with a second position in order to produce a table selection value.

5. A method according to claim 4, wherein two look-up tables are selected and new values for performing the look-up operation are determined by a process of linear interpolation.

6. A method according to claim 2, wherein said depth values are processed by calculating the logarithm for each of said values.

7. A method according to claim 6, wherein two look-up tables are selected and new values for performing the look-up operation are determined by a process of linear interpolation.

8. A method according to claim 6, wherein said values are shifted and an indication of the number of shifts made are supplied to look-up table means to produce an indication of the look-up table to be selected for the mapping.

9. A method according to claim 8, wherein two look-up tables are selected and new values for performing the look-up operation are determined by a process of linear interpolation.

10. A method according to claim 1, wherein two look-up tables are selected and new values for performing the look-up operation are determined by a process of linear interpolation.

11. A method according to claim 1, wherein said mapping to said locus of pixels includes said steps of linearly interpolating, identifying, and applying a correction factor to each coordinate of each pixel of said locus of pixels.

12. A method according to claim 11, further comprising the steps of scaling the interpolated coordinate and applying the correction factor to the scaled interpolated coordinate, followed by descaling the corrected coordinate to obtain the coordinate for the pixel to be mapped from the two dimensional input image.

13. A method according to claim 12, wherein said boundary points are vertices of the two dimensional polygon.

14. Image processing apparatus arranged to render a two dimensional output image comprised of pixels from three dimensional image data, wherein a random polyhedron is projected from a location of viewing as a two dimensional polygon having a boundary enclosing an area and defined in three dimensional space and pixel values from a two dimensional input image are mapped onto pixels within the projected polygon, comprising:

processing means including means for identifying at least two boundary points on said boundary of said polygon, for mapping pixels within said two dimensional input image corresponding to each of said at least two points on said polygon boundary according to a defined mapping function, for identifying a locus of pixels within said polygon extending between said at least two boundary points, and for mapping pixels within said two dimensional input image to each of said pixels of said locus of pixels within said polygon by (i) linearly interpolating at least one coordinate of each pixel along said locus of pixels to obtain an interpolated coordinate, (ii) identifying the look-up table corresponding to the location of viewing from which said two dimensional polygon was projected;

(iii) applying a correction factor from the set of correction factors in the selected lookup table to the interpolated coordinate to obtain a corrected coordinate for the pixel to be mapped from the two dimensional input image.

15. Apparatus according to claim 14, wherein said storage means is arranged to store a plurality of look up tables and a selector is arranged to select look up tables by processing depth (z) values.

16. Apparatus according to claim 15, wherein said selector is arranged to select two look up tables and said processor is arranged to interpolate values between values read from said look up tables.

17. Apparatus according to claim 15, wherein said selector is arranged to divide a first depth value by a second depth value to produce a table selection value.

18. Apparatus according to claim 17, wherein said selector is arranged to select two look up tables and said processor is arranged to interpolate values between values read from said look up tables.

19. Apparatus according to claim 15, wherein said selector processes depth values by calculating the logarithm of said depth values.

20. Apparatus according to claim 19, wherein said selector is arranged to select two look up tables and said processor is arranged to interpolate values between values read from said look up tables.

21. Apparatus according to claim 19, wherein said selector includes a shift register, means for shifting values in said register and processing means for processing said shifted values, to provide an indication of the required look up table.

22. Apparatus according to claim 21, wherein said selector is arranged to select two look up tables and said processor is arranged to interpolate values between values read from said look up tables.

23. Apparatus according to claim 14, wherein said selector is arranged to select two look up tables and said processor is arranged to interpolate values between values read from said look up tables.

24. An image processing apparatus according to claim 14, wherein said processing means applies a correction factor to both cartesion coordinates of each pixel of said locus of pixels.

25. An image processing apparatus according to claim 14, further comprising means for scaling the interpolated coordinate and applying the correction factor to the scaled interpolated coordinate, followed by descaling the corrected coordinate to obtain the coordinate for the pixel to be mapped from the two dimensional input image.

26. An image processing apparatus according to claim 14, wherein said boundary points are vertices of the two dimensional polygon.