Graphics display system using logic-enhanced pixel memory cells

• US 4,590,465 A
• Filed: 02/18/1982
• Issued: 05/20/1986
• Est. Priority Date: 02/18/1982
• Status: Expired due to Term

• Current Assignee: University of South Carolina
• Original Assignee: Henry Fuchs
• Inventors: Fuchs, Henry
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/349,818
• Time in Patent Office: 1,552 Days
• Field of Search: 340/703, 340/717, 340/723, 340/729, 340/727, 340/750, 340/798, 340/799, 365/220, 365/238
• US Class Current: 345/418
• CPC Class Codes: G06T 15/80 Shading
• CPC Class Codes: G09G 5/42 characterised by the display of patterns using a display memory without fixed position correspondence between the display memory contents and the display position on the screen

Abstract

The present invention provides a relatively inexpensive raster-scan type graphics system capable of real time operation, utilizing logic-enhanced pixels within an image buffer, permitting parallel (simultaneous) calculations at every pixel. A typical implementation would be as custom VLSI chips. In the sequence of most general applications, each polygon is operated upon in sequence, and the image is built up as the polygons are processed without the necessity of sorting. With respect to each successive polygon, the following operations are effected: (1) all pixels within the polygon are identified; (2) the respective pixels which would be visible to the observer, that is, not obstructed by some previously processed polygon, are determined; and (3) the proper color intensities for each visible pixel are determined.

Claims

1. A graphics display system comprising:

a display device including a plurality of individual picture elements (pixels), each said pixel being disposed at a predetermined position in a nominal display coordinate system;

processor means, responsive to data base signals representative of at least a portion of a visual three dimensional scene and perspective control signals applied thereto, for generating display coordinate data signals representative of said scene portion viewed from a perspective defined by said perspective control signals, said scene including at least one object, said display coordinate data signals comprising sequential representations of the spatial disposition and luminescent intensity of a plurality of component surfaces of said object in said scene portion;

preprocessor means, responsive to said display coordinate data signals, for selectively generating, in respect of each of said plurality of sequential component surfaces, respective coefficient signals indicative of coefficients of at least one equation representative of respective aspects of said each component surface;

image buffer means, responsive to said coefficient signals and including a respective individual cell corresponding to each said display device pixel, for determining, at each cell, the value of said equation in parallel at the positions of each said pixel, and selectively storing indicia of intensity values in each cell corresponding to a pixel within the component surface, which pixel is not obstructed from said perspective by any preceding sequential component surface; and

display control means, responsive to said stored intensity indicia, for controlling said display pixels in accordance with the intensity indicia stored in said image buffer means corresponding individual cell.

2. The system of claim 1 where:

said aspects include the edges of said component surface, the line of sight distances of said component surface at said pixel positions from said viewpoint, and the intensity values of the pixels enclosed by said component surface; and

said image buffer means comprises;

means, responsive to said coefficient signals, for generating, in parallel, respective edge equation value signals corresponding to the value of each edge equation having coefficients in accordance with said coefficient signals, at the coordinates of each of said display pixels and applying said respective equation value signals to the corresponding individual cells;

means, in each said cell, responsive to said applied edge equation value signals, for determining if the pixel corresponding to said cell is within said component surface, and for selectively disabling said cell in respect of said distance and intensity equation values if said corresponding pixel is not within said component surface;

means, responsive to said coefficient signals, for generating, in parallel, respective distance equation value signals corresponding to the value of each distance equation having coefficients in accordance with said coefficient signals, at the coordinates of each of said display pixels and applying said respective equation value signals to the corresponding individual cells;

means, in each said storage cell, selectively responsive to said applied distance equation value signals, for maintaining indicia of the line of sight distance of the closest previous component surface including said corresponding pixel, for determining line of sight distance of said component surface at said corresponding pixel position from said viewpoint, comparing said determined distance with said maintained previously closest distance, and disabling said cell with respect to said intensity equation value signals in respect of said component surface if said component surface is more distant along said line of sight than said previously closest distance; and

intensity rendering means, selectively responsive to said applied intensity equation value signals, for developing indicia of the intensity at said corresponding pixel as viewed from said viewpoint.

3. In graphics display apparatus of the type receptive of data base signals indicative of at least a portion of a scene, and including:

a display device having a plurality of individual picture elements;

processor means, responsive to said data base signals and control signals applied thereto, for generating display coordinate data signals representative of said scene portion viewed from a viewpoint defined by said control signals in a predetermined display coordinate system; and

an image buffer, including at least one cell corresponding to each pixel in said display, for selectively storing indicia of at least one visual intensity value for said corresponding pixel,

the improvement wherein;

each of said cells includes individual processing means, responsive to signals indicative of said display coordinate data signals and control signals applied thereto, for cooperating in the determination of said intensity value for the corresponding pixel.

4. In the apparatus of claim 3 the further improvement wherein said apparatus includes:

preprocessor means, responsive to said display coordinate data signals, for selectively generating respective coefficient data signals representative of the coefficients of predetermined equations; and

means, responsive to said coefficient data signals, for generating respective function value signals for each coordinate value in said display coordinate system, said function value signals being applied to the respective individual processor means of the cells corresponding to the pixels having the respective coordinate value.

11. The apparatus of claim 3 further comprising means for generating substantially concurrent, substantially indentical control signals to the individual processing means of each of said cells.

5. Graphics display apparatus of the type receptive of data base signals indicative of at least a portion of a scene, and including:

a display device having a plurality of individual picture elements (pixels)

processor means, responsive to said data base signal and control signals applied thereto, for generating display coordinate data signals representative of said scene portion viewed from a perspective defined by said;

control signals in a predetermined display coordinate system and an image buffer including at least one addressable cell corresponding to respective pixels in said display for selectively storing indicia of at least one visual intensity value for said corresponding pixel, the improvement wherein;

said apparatus further comprises preprocessor means, responsive to said display coordinate data signals, for selectively generating respective coefficient data signals representative of the coefficients of predetermined equations associated with said display coordinate data; and

said image buffer comprises;

means, responsive to said coefficient data signals, for generating respective equation value signals corresponding to each operative coordinate in said display coordinate system; and

at least one respective individual cell corresponding to each pixel in said display, said cell responsive to the equation value signals corresponding to the coordinates of said corresponding pixel, for cooperatively determining the intensity value of said corresponding pixel in said scene portion as viewed from said perspective.

6. The apparatus of claim 5 wherein said display coordinate data defines at least one closed unit surface in said scene portion, and wherein each said cell includes:

unit definition means, selectively responsive to said corresponding coordinate equation value signals and to initialization signals applied thereto, for selectively disabling said cell with respect to said equation value signals;

means, selectively responsive to said corresponding coordinate equation value signals and to preset signals applied thereto, for maintaining indicia of the unit surface previously closest along the line of sight from the corresponding pixel to said defined perspective, and for disabling said cell with respect to said equation value signals in respect of unit surfaces further from said perspective then said previously closest unit surface; and

intensity rendering means, selectively responsive to said corresponding coordinate equation value signals, for developing indicia of said corresponding pixel intensity in respect of a unit surface only if said unit surface at said corresponding pixel is not obstructed by any unit surface previously closer along the line of sight from said corresponding pixel to said defined perspective.

7. A method of generating a graphic display of a scene as viewed from a defined perspective utilizing a display device having a plurality of individual pixel elements, and a frame buffer including a respective cell corresponding to each said pixel, each said cell being capable of at least an enable state whereby said cell is receptive of data signals applied thereto and an inhibited state wherein said cell is not responsive to data signals applied thereto, said scene being represented by data signals defining a sequence of respective component surfaces of said scene in respect of spatial disposition and intrinsic visual intensity, comprising the steps of:

(a) repeating in respect of each component surface in sequence;

(a1) initializing the enable/inhibit state of each of said respective cells;

(a2) generating signals indicative of the coefficients of an equation of an edge of said component surface as a function of the coordinates of said display device pixels;

(a3) generating, from said edge coefficient signals, in parallel at each said cell, respective signals indicative of the respective value of said edge equation for each value of said coordinates of said pixels;

(a4) selectively adjusting the enable/inhibit states of individual cells in accordance with the value of said edge equation at the coordinates of said corresponding pixel;

(a5) repeating steps a2, a3, and a4 for each edge of said component surface;

(a6) generating signals indicative of the coefficients of an equation indicative of the visual intensities of the respective pixels within said component surfaces as a function of the coordinates of said pixels;

(a7) generating, in parallel at each said cell, from said intensity plane equation coefficients, respective signals indicative of the respective value of visual intensity for each value of coordinates of said pixels;

(a8) selectively storing, in each of said cells in an enabled state, the respective value of visual intensity at the coordinates of the corresponding pixel; and

(b) controlling said display device in accordance with the respective intensity values stored in said individual cells after repeating the above steps (a) in respect of all said component surfaces.

8. The method of claim 7 wherein steps (a) in respect of each component surface include before said selectively storing step (a8):

generating signals indicative of the coefficients of an equation representing the distance of said component surface from said defined viewpoint as a function of the coordinates of said pixels;

generating, in parallel at each said cell, from said distance coefficient signals, respective signals indicative of the respective value of said distance equation at the coordinates of each of said pixels; and

selectively disabling said respective cells in accordance with said distance equation value at the coordinates of said corresponding pixel.

9. Apparatus for generating a graphic display of a scene as viewed from a defined viewpoint, comprising:

means for generating sequential sets of data signals defining a sequence of respective component surfaces of said scene in respect of spatial disposition and intrinsic visual intensity;

a display device having a plurality of individual pixel elements;

a frame buffer including a respective cell corresponding to each said pixel element, each said cell being capable of at least an enabled state whereby said cell is receptive of data signals applied thereto and an inhibited state wherein said cell is non-responsive to data signals applied thereto;

means, responsive to said data signal sets, for initializing the enable/inhibit state of each said respective cells in respect of each sequential component surface;

means, responsive to said data signal sets, for generating, in sequence, signals indicative of the coefficients of equations representative of the respective edges of said defined component surface as a function of the coordinates of said display device pixels;

means at each of said cells responsive to said edge coefficient signals, for generating, for each said edge equation in sequence, sets of signals indicative of the respective valeus of said edge equation at the respective coordinates of said pixels;

means, for selectively adjusting the enable/inhibit states of individual cells in accordance with the value of said edge equation at the coordinates of said corresponding pixel;

means, at said cells responsive to each said data signal set in sequence, for generating, in parallel, signals indicative of the coefficients of an equation indicative of the visual intensities of the respective pixels within said defined component surface as a function of the coordinates of said pixels;

means, responsive to said intensity equation coefficient signals, for generating a set of signals indicative of the respective values of said intensity at the coordinates of said pixels;

means for selectively storing, in each of said cells in an enabled state, the respective value of visual intensity of said defined component surface at the coordinates of the corresponding pixel; and

means for controlling said display device in accordance with the respective intensity values stored in said individual cells after the data signal sets in respect of all said component surfaces have been responded to.

10. The apparatus of claim 9 further including:

means, responsive to said data signal sets in sequence, for generating signals indicative of the coefficients of an equation representing the distance of the pixels in said defined component surface from said defined viewpoint as a function of the coordinates of said pixels;

means at said cells responsive to said distance plane coefficient signals, for generating, in parallel for each pixel, a set of respective signals indicative of the respective values of said distance equation at the coordinates of each of said pixels; and

means for selectively disabling said respective cells prior to operation of said means for selectively storing in accordance with said distance equation value at the coordinates of said corresponding pixel.

12. A system for displaying an image on a display, said display including a plurality of respective display elements, said system comprising:

display parameter calculating means for calculating at least one display parameter, said calculating means comprising;

(1) an array of respective cells, each of said display elements associated with at least one of said cells, each of said respective cells comprising;

(a) adding means for calculating an intensity value for the display element associated with said cell in response to information transmitted to said cell, and

(b) means for storing said calculated intensity value; and

(2) multiplying means for transmitting said information representing an image to be displayed, comprising distinct combination of data input thereto, to each of said cells; and

means for controlling said plurality of display elements in response to said stored intensity values.

13. A system as in claim 12 wherein said multiplying means includes:

means for producing a plurality of signals representing said image, predetermined ones of said plurality of signals representing predetermined portions of said image; and

means for applying said plurality of signals to said array.

14. A system as in claim 13 wherein said applying means applies a different combination of said plurality of signals to each cell in said array, predetermined combinations of said plurality of signals representing predetermined portions of said image.

15. An apparatus as in claim 14 wherein said array further includes means for arranging said cells in a predetermined manner, the combination of said plurality of signals applied to each cell being determined by the position of the cell in said array.

16. A system as in claim 15 wherein the relative positions of said cells in said array correspond to the relative positions on said display of the display elements associated with said cells.

17. A system as in claim 14 wherein said parameter calculating means further includes:

means for defining a viewing plane, each of said cells in said array associated with a predetermined point on said viewing plane, and

projecting means for projecting a representation of at least a first surface in a three-dimensional scene onto said viewing plane,

wherein the combination of signals applied to any cell represents the projection of the representation of said first surface onto the predetermined point of said viewing plane associated with said any cell.

18. A system as in claim 17 wherein:

said calculating means further includes means for specifying at least one aspect of said projection by coefficients of a predetermined planar equation;

said plurality of signals producing means includes;

tree processing means for multiplying, in parallel, a plurality of values of coordinates of said viewing plane by said coefficients to obtain a plurality of products, and

means for converting said products into said plurality of signals; and

wherein said adding means in each of said cells combines the ones of said plurality of signals applied thereto to obtain the value of said planar equation at the point of said viewing plane associated with said each cell.

19. A system as in claim 18 wherein said specifying means successively specifies, by said coefficients, at least two of:

the position of said projection on said viewing plane,

the depth of said first surface in said three-dimensional scene, and

the shading of said first surface.

20. A system as in claim 19 wherein each of said cells further includes comparing means, responsive to said combination of signals, for the determining whether the point on said viewing plane associated with said cell is enclosed by said projected representation.

21. A system as in claim 20 wherein comparing means also determines whether the view of said first surface is hidden by another surface in said scene having a depth in said scene, with respect to a predetermined viewing perspective, less than the depth of said first surface.

22. A system as in claim 19 wherein each of said cells further includes comparing means, responsive to said combination of signals, for determining whether the view of said first surface is hidden by another surface in said scene having a depth in said scene, with respect to a predetermined viewing perspective, less than the depth of said first surface.

23. A system as in claim 22 wherein each of said cells further includes means for storing the depth of said another surface, said comparing means also responsive to said stored depth.

24. A system as in claim 17 wherein said plurality of signals producing means includes means for successively specifying, by said combination of signals, at least two of:

the position of said projection on said viewing plane,

the depth of said surface in said three-dimensional scene, and

the shading of said first surface.

25. A system as in claim 24 wherein each of said cells further includes comparing means, responsive to said combination of signals applied to said cell, for determining whether the point on said viewing plane associated with said cell is enclosed by said projected representation.

26. A system as in claim 25 wherein said comparing means also determines whether the view of said first surface is hidden by another surface in said scene having a depth in said scene, with respect to a predetermined viewing perspective, less than the depth of said first surface.

27. A system as in claim 24 wherein each of said cells further includes comparing means, responsive to said combination of signals applied to said cell, for determining whether the view of said first surface is hidden by another surface in said scene having a depth in said scene, with respect to a predetermined viewing perspective, less than the depth of said first surface.

28. A system as in claim 27 wherein each of said cells further includes means for storing the depth of said another surface, said comparing means also responsive to said stored depth.

29. A system as in claim 17 wherein said plurality of signals producing means includes means for offsetting the levels of the signals applied to at least a first cell by a predetermined amount from the levels of the signals applied to at least a second cell associated with a point of said viewing plane which is adjacent to the point of said viewing plane represented by said first cell.

30. A system as in claim 14 wherein said adding means of each of said cells combines the signals applied to said each cell to obtain said intensity value.

31. A system as in claim 14 wherein:

said plurality of signals producing means includes means for setting each of said plurality of signals to a value proportional to a coefficient of a planar equation; and

said adding means of each of said cells combines the values of the signals applied thereto to obtain a value of said planar equation.

32. A system as in claim 12 wherein:

said calculating means further includes;

means for defining a viewing plane, each of said cells in said array being associated with a predetermined point on said viewing plane,

means for defining a three-dimensional scene to be imaged, said scene including at least a first surface, and

projecting means for projecting a representation of said first surface onto said viewing plane;

said multiplying means includes means for transmitting the position of the projection of said representation on said viewing plane and the depth, from a predetermined viewing perspective, of said first surface in said scene; and

each of said cells further includes comparing means for successively determining, in response to said transmitted information, whether the point on said viewing plane associated with said each cell is enclosed by said projection and whether the view of said first surface is hidden by another surface in said scene having a depth in said scene, with respect to said predetermined viewing perspective, less than the depth of said first surface.

33. A system as in claim 32 wherein each of said cells further includes means for storing the depth of said another surface, said comparing means also being responsive to said stored depth.

34. A system as in claim 32 wherein each of said cells further includes disabling means, responsive to the determination of said comparing means, for selectively disabling said comparing and adding means from responding to said transmitted information.

35. A method for displaying an image on a display having a plurality of respective display elements, said method comprising the steps of:

(1) deriving a plurality of different signals representing corresponding different portions of an object to be displayed from at least one value specifying said object;

(2) applying a unique combination of said plural signals to an input of each cell in an array of respective cells, each of said display elements associated with at least of one of said cells;

(3) calculating, at each of said cells, an intensity value for the display element associated with said cell in response to at least one said combination of signals applied thereto by said applying step (2);

(4) storing said calculated intensity value at each of said cells; and

(5) controlling said plurality of display elements in response to said stored intensity values.

36. A method as in claim 35 wherein said controlling step (5) includes the step of applying to said display elements intensity values stored in cells having positions in said array corresponding to the relative position of the display elements on said display.

37. A method as in claim 35 further including:

defining a viewing plane, each of said cells in said array associated with the predetermined point on said viewing plane;

projecting a representation of at least a first surface of said object in a three-dimensional scene onto said viewing plane; and

representing, by the combination of signals applied to each cell, the projection of the representation of said first surface onto the predetermined point of said viewing plane associated with said cell.

38. A method as in claim 37 wherein:

said method further includes specifying at least one aspect of said projection by coefficients of a predetermined planar equation;

said step of deriving a plurality of signals includes;

multiplying, in parallel, a plurality of values of coordinates of said viewing plane by said coefficients to obtain a plurality of products, and

converting said products into said plurality of signals; and

said calculating step (3) includes combining the ones of said plurality of signals applied to said cells to obtain the value of said planar equation at the points of said viewing plane associated with said cells.

39. A method as in claim 38 wherein said aspect-specifying step includes successively performing at least two of:

specifying the position of said projection on said viewing plane;

specifying the depth of said first surface in said three-dimensional scene; and

specifying the shading of said first surface.

40. A method as in claim 39 further including the step of determining at each cell, in response to said combination of signals applied thereto, whether the point on said viewing plane associated with said cell is enclosed by said projected representation.

41. A method as in claim 40 further including the step of determining at each cell, in response to said combination of signals applied thereto, whether the view of said first surface is hidden by another surface in said scene having a depth in said scene, with respect to a predetermined viewing perspective, less than the depth of said first surface.

42. A method as in claim 39 further including the step of determining at each cell, in response to said combination of signals applied thereto, whether the view of said first surface is hidden by another surface in said scene having a depth in said scene, with respect to a predetermined viewing perspective, less than the depth of said first surface.

43. A method as in claim 42 further including the step of storing the depth of said another surface at each of said cells, said hidden surface determining step also being responsive to said stored depth.

44. A method as in claim 37 wherein said deriving step (1) includes the step of successively performing at least two of the steps of:

specifying the position of said projection on said viewing plane;

specifying the depth of said surface in said three-dimensional scene; and

specifying the shading of said first surface.

45. A method as in claim 44 further including the step of determining, at each of said cells in response to said signals applied thereto, whether the point on said viewing plane associated with said cell is enclosed by said projection.

46. A method as in claim 45 further including the step of determining, at each of said cells in response to said signals applied thereto, whether the view of said first surface is hidden by another surface in said scene having a depth in said scene, with respect to a predetermined viewing perspective, less than the depth of said first surface.

47. A method as in claim 44 further including the step of determining, at each of said cells in response to said signals applied thereto, whether the view of said first surface is hidden by another surface in said scene having a depth in said scene, with respect to a predetermined viewing perspective, less than the depth of said first surface.

48. A method as in claim 47 further including storing, at each of said cells, the depth of said another surface, said hidden surface determining step also responsive to said stored depth.

49. A method as in claim 37 wherein said deriving step (1) includes offsetting the levels of the signals applied to at least a first cell by a predetermined amount from the levels of the signals applied to at least a second cell associated with a point of said viewing plane which is adjacent to the point of said viewing plane represented by said first cell.

50. A method as in claim 35 wherein said calculating step (3) includes the step of combining at each cell the signals applied thereto.

51. A method as in claim 35 wherein:

said deriving step (2) includes the step of defining a planar equation representative of said image, said equation having at least one coefficient;

said applying step includes the step of applying values proportional to said coefficient to said cells; and

said calculating step (3) includes a step of deriving, at each said cell, a value of said planar equation from the values of the signals applied thereto.

52. A method as in claim 35 wherein:

said method further includes the steps of;

defining a viewing plane, each of said cells in said array associated with a predetermined point on said viewing plane,

defining a three-dimensional scene to be imaged, said scene including at least a first surface, and

projecting a representation of at least said first surface onto said viewing plane;

said applying step (2) includes the step of applying signals representing the position of the projection of said representation on said viewing plane and the depth of said first surface in said scene to said array of cells; and

said method further includes the step of successively performing at least two of;

determining, at each of said cells in response to said applied signals, whether the point on said viewing plane associated with said cell is enclosed by said projection, and

determining, at each of said cells in response to said transmitted information, whether the view of said first surface is hidden by another surface in said scene having a depth in said scene, with respect to a predetermined viewing perspective, less than the depth of said surface.

53. A method as in claim 52 further including the step of storing, at each cell, the depth of said another surface, said hidden surface determining step also being responsive to said stored depth.

54. A method as in claim 52 further including the step of selectively disabling, at each of said cells, the performance of said enclosure determining step, hidden surface determining step and calculating step (3).