JP2007141196A - Polygon/silhouette line/anti-aliasing circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow high quality anti-aliasing drawing to a shadow and a polygon contour line at comparatively slight costs. <P>SOLUTION: This polygon/silhouette line/anti-aliasing circuit is provided with a means for storing the contour line of a polygon and a means for storing contour line information in which the contour line crosses a grid, a means for performing hidden surface removal by a coordinate point inside the polygon and the contour line information, deleting the contour line to be a polygon sharing side from a buffer to store only the contour line information of a silhouette line pixel, a means for reading the stored contour line information to judge positions inside and outside the polygon when the point is on the silhouette line and a means for attenuating a luminance value in order to determine luminance of the shadow. As for anti-aliasing of a viewpoint coordinate system, silhouette line information of the polygon is stored, color information is further stored in the contour line information, the contour line information is read for the luminance of the pixel in which a drawing point becomes the silhouette line and the color information is proportionally distributed from each area ratio crossing in pixel grid to determine the luminance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a computer graphics drawing technique, and belongs to the logic circuit field of antialiasing processing for reducing the jaggy phenomenon of a silhouette line of a visible projection figure.

Supersampling, multi-sampling, boundary edge method, and the like are known as computer graphics techniques for reducing the jaggy or alias (stepped waveform) phenomenon of a display figure that occurs in a raster display. They are also used to reduce aliases on shadow silhouette lines. In the boundary edge method, which is known as the lowest cost method (both hardware and software), a pixel is regarded as a grid space (square), and a polygon is obtained by dividing a polygon outline by intersecting the grid, that is, a polygon. The inner and outer areas are obtained, and the luminance (color) between the outside and inside is proportionally halved by the area ratio to obtain the luminance of the pixel point. As a method of determining the brightness from the relationship between the contour line and the grid, the method using the slope of the contour line, the coordinate value of the contour line intersection with the grid (straight line generator decimal point), the major axis minor axis value, the start point end point, etc. No. 57-191687 and Japanese Patent Laid-Open No. 58-55981. Japanese Patent Laid-Open No. 2002-352253 using the straight line information as anti-aliasing of a polygon edge is known. In Japanese Patent Laid-Open No. 2002-352253, a two-dimensional buffer having the same size as the drawing space is provided, outline line information is stored in this buffer, and after drawing a polygon, the luminance of the outline line pixel and its surrounding pixels is synthesized to create a silhouette line. The upper brightness was determined. In this method, since the maximum number of contour lines per pixel cannot be predicted before drawing, the word size (bit field) per pixel of the buffer cannot be determined in advance. In the above-mentioned Japanese Patent Application, a plurality of contour line information per pixel can be stored, but if a certain number is exceeded, a multi-intersection flag is set, and when this flag is detected after drawing, the means for distributing the luminance of the pixel by area ratio The luminance was determined by switching to a means for taking the average value of the peripheral luminance. With this method, it is impossible to determine an accurate luminance for an image exceeding a predetermined number of intersections, and aliases remain in some graphics.
In addition, in a system that performs smoothing of shadow silhouette lines, it is necessary to accurately determine whether the drawing point is located inside (shadow) or outside (irradiation) of the outline in the grid. I can't. Furthermore, in the above-mentioned JP, the calculation of the polygon crossing area in the grid is performed at the video scanning stage after all the drawing is completed, and not only the information in one grid but also the surrounding grids are determined for luminance. The circuit scale has been increased because luminance must also be referenced.
On the other hand, in the polygon rendering method, an object is represented by a set of polygons (mainly triangles) as a surface model. Polygons within a curved surface share sides with neighboring polygons, so most polygon sides are not silhouette lines. To determine whether the polygon side of the projected object is a silhouette line or a shared side in a curved surface, in the system in which the hidden surface is deleted when the normal of the polygon surface is the back of the viewpoint direction, the shared side is Sides that do not have become silhouette lines. In other words, when the same polygon outline is written twice, it can be considered that the side is in contact with the adjacent polygon. For the detection of shared edges, the above-mentioned Japanese Patent Application discloses a method for storing outline information in a two-dimensional buffer and comparing this with postscript information, but it is possible to store intersection information of a plurality of outlines. Providing a buffer for a large drawing space causes a cost problem and will be described later.

It is not possible to cope with individual solutions for each of the more complicated intersection conditions up to 1-4. Further, in the above-mentioned Japanese Patent Application Laid-Open No. 2004-208, an interpolation circuit such as a linear generator or DDA is composed of an adder / subtracter (so-called conventional DDA structure) separated into an integer part and a decimal point part. There was a limit to the accuracy range because it was an arithmetic process.

  In addition, the conventional straight line generator normally provided for drawing a polygon cannot identify all grids where polygon outlines intersect. This is because the output value of the coordinate value from the straight line generator is rounded by the nearest neighbor method, and when the outline line grazes the grid, the adjacent grid is not the actual intersection grid but rounded. It is regarded as a passing pixel. As long as the luminance of the grid intersecting the contour lines is obtained from the intersection area ratio, it is necessary to target the grid where the silhouette lines actually intersect, not the coordinate values obtained from the linear equation or DDA. This cannot be obtained by a conventional straight line generator (interpolation circuit) or DDA that calculates the nearest neighbor method.

  It is an object of the present invention to detect a silhouette line, to determine a polygon inside / outside of a drawing point in a grid serving as a silhouette line, and to form a logic circuit thereof.

In disclosing means for solving the problems, the manner in which the outline of the polygon handled by the present invention intersects the grid is shown below. Whether outlines passing through the grid are silhouette lines or shared sides with adjacent polygons is determined by outline line information. Most of the crossing states of the contour lines in the grid are state examples up to 1-4 and combinations thereof.
1. 1. When one side intersects in the grid 2. When there are two or more sides in the grid 2-1. When the sides do not match in the same polygon 2-2. When the sides are the same in the same polygon 2-3. When each polygon is different and the sides do not match 2-4. 2. When each polygon is different and the sides match If there is one vertex in the grid:
3-1. Vertex by connecting the left and right edges (start / end V-shaped)
3-2. Vertex by either left or right side (obtuse angle V shape)
3-3. When the left and right sides have the same grid intersection and slope (complete overlap type)
4). When multiple polygon vertices exist in the same grid 4-1. Each polygon shares one side with another polygon and the grid intersections on the other side are different (open plane)
4-2. Each polygon is closed with one side shared with other polygons (closed plane)
4-3. When all polygon sides have the same grid intersection and slope (overlap) 4-4. When each polygon side independently shares only the vertex 4-5. When two or more different polygon vertices exist independently

In order to identify the silhouette line information and the intersection grid of the silhouette lines, the polygon outline is interpolated at the same time for each of the left side and the right side and the coordinates of the left side and right side coordinate points for each horizontal axis. Output sequentially or simultaneously, and then horizontally interpolate between the left and right end points.

  In the present invention, a buffer (silhouette line buffer) for storing outline line information is provided, and an outline line flag indicating the passage of the outline line, and outline line valid flag, grid intersection coordinate point, intersection axis, inclination, left and right as outline line information Each of the side, the x-axis code, and the distance (z value) from the projection center is stored. Here, the grid intersection coordinate point is different from the conventional method (conventionally, the DDA decimal point on the short axis side), and is a coordinate value that intersects the grid side regardless of the long or short axis. The intersecting axis is an axis (x or y) at which the polygon outline enters and intersects the grid. Therefore, the intersection axis, the left and right sides, the x-axis code, and the outline valid flag are each represented by 1 bit. Crossed coordinate values and slopes are real numbers or floating-point values with arbitrary ranges (the grid unit is 1.0 on one side, the slope of the y-axis is always positive, and the sign bit is separately provided for the x-axis. (Each number is less than the positive decimal point).

In the present invention, a buffer having 1 bit per pixel (hereinafter referred to as a plane buffer) is provided as a silhouette line buffer rather than a conventional structure for storing outline information of several tens of bits per pixel having the size of the entire drawing space. In this plane buffer, “1” is set for the pixels through which the outline passes, and “0” is set for the pixels other than the outline. Further, as a buffer for storing outline information, a one-dimensional buffer having addresses corresponding to the number of pixels through which the outline passes is provided (hereinafter, this buffer is referred to as an information buffer). Therefore, unlike the conventional method, the buffer for storing the outline information does not have a capacity for the entire drawing space. The information buffer can store, for example, three outline information for each address (in word units). If three or more polygon outlines intersect in the same grid and overflow this storage area, the word length is expanded and buffered. In this way, when a large number of outline lines intersect the same grid, the information buffer is expanded every three lines, and outline information is sequentially stored. The extension buffer part is also extended in units of three outline information, for example. On the other hand, when the outline of the polygon that is the object name enters the grid, the outline information is switched to the extended buffer even if the storage area remains in the word of the previous information buffer. And remember.
In the present invention, one background buffer (hereinafter referred to as BK buffer) is provided for each address of the information buffer (for each silhouette line / grid). The BK buffer stores the distance (z value) from the projection center of the polygon serving as the grid background. Default is infinity.
Compared to the total number of pixels in the drawing space, the number of pixels occupied by the silhouette line is usually less than one hundredth, and a plurality of contour lines and polygon vertices are less frequently overlapped in the same grid. Further, the maximum number of intersections of one polygon (triangle) in one grid is three. Adjacent polygons share one side, and the shared side is not a silhouette line (the outline line valid flag is reset if it coincides with a polygon side that shares the outline line). In this case, there are two lines. From this result, in the present invention, at least three outline information can be written for each address of the information buffer, and when this number is exceeded, it is stored in the expanded word. As a physical structure of the buffer, a method may be used in which the word of the information buffer has a storage capacity for one set of outline information, and the buffers are dynamically linked for each outline information after two sets.

In the present invention, the link from the plane buffer to the information buffer is associated by using, as an indirect address, a value generated by the hash method, for example, using the outline coordinate values (x, y) of the plane buffer as input variables. Therefore, the size of the information buffer that can be exclusively addressed is 2 ^m words when divided by an m-order function. When the set m value is small and the addresses conflict even though the x and y addresses of the planar buffer are different, a link address is generated and the buffer word is expanded. As a link between information buffers, a dynamic method in which an indirect address is used as data to generate and store an address using a polynomial remainder value having a different m value can be considered. (Up to 4 words, for example, a maximum of 12 outline information can be stored as 3 outline information per word), and even if the information buffer has the same bit length for each address, 2 Compared with the structure of the dimensional array, the capacity is not large.

  When storing the contour lines in the information buffer, the z values of the contour lines already stored are read and compared. In shadow antialiasing, the closest contour to the light source, and in polygon antialiasing, the contour information closest to the viewpoint is in the first field in the information buffer word, the next contour in the information buffer word is in the second field, and the next Is stored in the order of the third field. Therefore, when the z value of the later-written polygon is closest to the light source or the viewpoint, the information of each field is moved to the lower field. On the other hand, when the buffer information is deleted due to the shared side, the information is packed in the upper direction.

  The z-value of the outline is compared by storing the z-value of the outline by providing a z-buffer (a bit field for storing the z-value for each word of each information buffer), and this z-value and the postscript outline In the normal image memory system, a set of buffers is provided to store the z value closest to the viewpoint or the light source in the normal image memory system. There is no buffer for storing the second and subsequent viewpoints or z values close to the light source. In the present invention, each z buffer up to a predetermined proximity number (practically up to 3-4 level) is prepared in the information buffer.

  Whether the outline is a silhouette line or a polygon shared side is determined by the internal / external direction of each side of the outline that intersects the grid (postscript) and the outline of the outline already stored in the information buffer (preface) Are contradictory (in the direction away from each other) and the contour line information other than this direction matches, the contour line is regarded as a polygon connection boundary (side) and not a silhouette line. On the other hand, in the direction where the left and right sides are opposite (facing each other), even if all the outline line information matches, only two sides match in drawing projection. It cannot be determined as a connection boundary. Furthermore, the above determination is satisfactory for polygons on the same curved surface, and if the curved surfaces are different, the connection boundary cannot be determined even if the trailing outline and the leading outline are completely overlapped and the side directions are contradictory. . Therefore, in the present invention, when it is determined that the contour line of the polygon has a different curved surface, the information is stored in a different buffer (an extended portion of the information buffer). On the other hand, it is not necessary to memorize the outline information of the polygon completely behind the curved surface. Whether or not the outline crossing grid is completely positioned behind the polygon can be determined only at the stage of the interior painting process of the polygon. Therefore, in the present invention, also in the span interpolation processing, the contour line flag of the plane buffer is read using the interpolation coordinate value, and when the grid with the flag set is detected, the span interpolation z value and the information buffer are stored. The z value is read and compared, and if the span interpolation side is closer to the viewpoint or light source than the z value of all information buffers, the filled polygon is assumed to be located in front of all images, and the flag of the plane buffer To reset. In this case, regarding the grid on the contour line during the span interpolation (left and right start and end points and y-axis bottom and top sides), there is a possibility that the polygons in the grid area are not overlapping but crossing. is there. Therefore, in the present invention,

Therefore, since the span interpolation is executed immediately after the outline interpolation, the identifier at the time of the outline interpolation (this identifier is the order value described in the next section in the present invention) is taken over by the span interpolation circuit, and at the stage of span interpolation. When the contour line information is read from the buffer, if there is a match in the order value, the grid is not reset as the contour line of the polygon being span-interpolated. If there is no match in the order value and the z value of the buffer outline information is far from the z value of the span interpolation, the outline is located behind the polygon being spanned. Regardless, reset the distant outline information. If the far outline is the only one in the grid, the plane buffer flag is also reset. On the other hand, in the processing described above, when the set value of the set / reset grid does not match the span interpolation sequence value and the plane buffer flag is set (the polygon being span-interpolated is located far from the outline of a different polygon) Is also compared with the z value of span interpolation and the z value of the BK buffer. If the z value of the BK buffer is closer to the viewpoint than the z value of span interpolation, the BK buffer is left as it is, and if it is far away, the BK buffer is replaced with the z value of span interpolation.

The determination of whether or not each polygon is a specific object has means for setting the object name as one of the outline line information as disclosed in JP-A-2002-352253. In the present invention, The object identifier is used for switching the extension buffer in the information buffer, and is not used as an identifier for storing each outline. The present invention uses an order value as a polygon identifier and adds it to each outline information. The order value is a value that is sequentially updated from 0 for each object identifier and starts from 0 again when an appropriate value is obtained. The arrangement of objects is usually geometrically local, and the probability of an object falling into one grid is not so high (for example, 14 bits are enough for about 10,000 objects). The buffer for storing the sequence value is placed on the information buffer instead of the plane buffer. As a result, the buffer capacity for storing the sequence value is small. These object identifiers and order values are used to switch buffers for each object, and in the case of order values within the same identifier, check for the presence of a shared edge condition. That is, when the identifiers are the same and the foreword and the afterword order values are the same, it means that two sides of the same polygon intersect in the same grid, and the outline information is stored in the current information buffer. On the other hand, if the order values are different, the outline information is written in the current buffer if the information buffer does not overflow, and in the next extended buffer after the information buffer if the information buffer overflows. A pointer indicating the current buffer is added in the word of the information buffer or one pointer register is provided. In the first buffer access with a different order value, the ID (identifier) of the information buffer is written to the current buffer (or register). The information buffer ID is a buffer number (0 is an information buffer, 1 is a first extension buffer, 2 is a next extension buffer, etc.) and a word field number (up to 0-2). Thereafter, the sequence value and the buffer ID are simultaneously compared for each access. For example, if the object changes, the previous sequence values become inconsistent, the first buffer of the information buffer is already used, and the second (extended) buffer is unused, the second buffer is used as the current buffer pointer. ID and unused word field number are set. Thereafter, the second buffer is accessed as long as the order value does not change or as long as there is no free space.
With respect to the buffering of the order value, it is possible to store one in the information buffer instead of the method of buffering the order value for each information buffer. That is, if it is assumed that the contour line interpolation and the span interpolation are always processed in the pipeline order, the sequence value storage buffer is not stored in each of the information buffers, but if the pipeline register is used, the span interpolation stage is not stored. The contour line information of its own polygon can be identified, and the contour line reset determination process at the span interpolation stage described above can be performed.

  From the above, in the present invention,

The following processing is performed for the aspects up to 1-4. Item 1 stores outline information in the information buffer. Item 2-1 stores two outline information in the same word of the information buffer. Item 2-2 is a case where the polygon is parallel or reduced to the line-of-sight direction and the outline lines match, and the two pieces of outline line information are stored in the same buffer word. In section 2-3, the objects are the same and the order value does not change, but when the polygons are different, the two pieces of outline information are stored in the same buffer word. In item 2-4, when the objects are the same and the internal and external directions are contradictory, the outline is regarded as a shared edge of the two polygons, and both the foreword outline information and the afterline outline information stored in the buffer are deleted ( Reset the outline flag in the buffer). If there is no outline information in the information buffer due to erasure, the outline flag of the plane buffer is also reset. On the other hand, if only the opposite outline information is the same object, the object includes a concave surface, and the postscript information is stored in the buffer. In this case,

In this example of buffer capacity, up to three pieces of outline information can be stored. This number can be increased arbitrarily. If the object is different in the case of item 2, the outline information is newly stored in the extended information buffer. Further, when the outline line stored in the buffer is completely behind the polygon by the hidden surface elimination process during the polygon filling process (span interpolation), all outline line information behind the polygon is erased. As a result, when the buffer word or the extension buffer becomes blank, the upper word is moved to pack the empty word. Items 3-1 and 3-2 store the two left and right sides respectively in the same information buffer word. Item 3-3 is a case where the inner and outer directions are opposite and the other contour line information all match, and stores each of the left and right sides. In Section 4-1, the outline of the afterword has a vertex in the grid (and thus includes two sides), and the grid has an already stored outline, and one of the outline and the outline of the latter If there is a conflict in the internal and external directions and the other contour line information matches, the matched contour line is erased from the buffer (reset the contour line flag), and the matched edge is also stored in the postscript information do not do. Only the outline information that does not match the afterword is newly stored in the buffer. Item 4-2 is a case where one side of all outlines is the same as one side of the outline line written later, for example, as a vertex of a sphere, and all sides are connected sides. All outlines in are reset. Item 4-3 is, for example, when the sides of the polygon are reduced and overlapped, and if there is a conflict between the outline of the later writing and the inside / outside direction of the outline already stored, it is reset. As a result, if the polygon is not closed, two opposing outlines will remain in the buffer. The item 4-4 resets only the case where the inside and outside directions of the outline line conflict and the other outline line information matches. In the item 4-5, all outlines are stored. However, the hidden surface removal result may include a reset result. The maximum memory number is determined by the number of buffer expansions. Item 4-6 is the same processing as item 4-5.

In polygon drawing, necessary information (vertex coordinate value, normal line, light source incident angle, line-of-sight vector, etc.) is defined for polygon vertices, the definition information is interpolated along the outline line connecting the polygon vertices, and then horizontal By performing span processing for further interpolation between points on the left and right sides of the contour line intersecting the axis from the bottom to the top on the y-axis of the polygon, the interpolation values of the vertex definition information of all the points inside the polygon are obtained. In interpolation processing along an outline, generally, an integer part of a coordinate value obtained from a linear expression or a DDA circuit constituting an outline interpolation circuit is determined as a pixel coordinate value. At this time, the straight line when the outline is inclined to the x-axis side with respect to the inclination of 45 degrees is called the x-axis major (long and narrow) and the y-axis minor (short axis). Call the opposite. Interpolation is obtained by substituting major axis coordinate values. An integer value is used as the assigned coordinate value. Equation (1) is an x-axis major and equation (2) is a linear equation for y-axis major. Let the start point and end point of the straight line be (x0, y0) and (x1, y1), respectively. In equation (1), Xi substitutes the distance between grids from the start point (x0) to the end point of the straight line to obtain the y coordinate value. In equations (1) and (2), Yi and Xi are integer values, and Yf and Xf are decimal values. (Xi, Yi) obtained as a result is a pixel coordinate point, that is, a straight line passes through the grid with the integer value of (Xi, Yi) as the grid origin.
Yi + Yf = {(y1-y0) / (x1-x0)} (Xi-x0) + y0 (1)
Xi + Xf = {(x1-x0) / (y1-y0)} (Yi-y0) + x0 (2)
If the nearest neighbor method is used, for example, in equation (1), when the decimal point value Yf of the straight line satisfies 1> Yf ≧ 0.5, (Xi, Yi + 1) becomes the pixel coordinate point by rounding off. That is, the conventional DDA rounds and adds 0.5 to the equation (1) and uses only the integer value on the left side. In this determination method, although a straight line intersects the (Xi, Yi) grid, some intersecting grids may not be regarded as passing points. As a result, the coordinate points obtained from the linear formula or DDA do not include all intersecting grids. On the other hand, in anti-aliasing or soft shadow for obtaining the area ratio inside and outside the polygon with a straight line intersecting the grid as a boundary, it is necessary to obtain all grid coordinates through which the outline passes and the area ratio.

表１において、Ｙｆはｙ軸の小数点部、Ｘｆはｘ軸小数点部、ΔＳはｘ軸メジャーの場合は（ｙ１−ｙ０）／（ｘ１−ｘ０）、ｙ軸メジャーの場合は（ｘ１−ｘ０）／（ｙ１−ｙ０）となる。グリッド点は本発明の、外郭線が交差するグリッド座標を示し、一方、ＤＤＡ画素点は最近傍法における小数点部が丸められた座標値であり、これが従来のポリゴンの塗りつぶしに用いる座標値である。In the present invention, in the outline interpolation circuit for filling the polygon, unlike the above-described conventional method, the integer part and the decimal point part are obtained without adding 0.5, and the grid coordinate point is the integer part (therefore, in the present invention). The rounding of the coordinate points is not rounded off, but rounded off), and the intersection condition is obtained from the long and short axes, the slope, and the decimal point values, and all grids are detected. As an example of this determination, the present invention can determine grid points using the algorithm shown in Table 1.

In Table 1, Yf is the decimal point part of the y-axis, Xf is the decimal part of the x-axis, ΔS is (y1-y0) / (x1-x0) for the x-axis major, and (x1-x0) for the y-axis major. / (Y1-y0). The grid points indicate the grid coordinates at which the contour lines of the present invention intersect, while the DDA pixel points are the coordinate values with the decimal point rounded in the nearest neighbor method, which are the coordinate values used for conventional polygon filling. .

  In the polygon filling process, the present invention and the conventional linear expression and DDA are the points that the grid points in Table 1 are output as pixel coordinate values in the present invention. As a result, for example, when the x-axis coordinate value is substituted into the linear equation in the x-axis measure, not only one output coordinate point but also two (Xi, Yi) and (Xi, Yi + 1) becomes a passing grid point.

It is necessary to draw a shadow to determine whether the drawing point in the grid (the decimal part of the interpolation value; hereinafter referred to as the sampling point) is inside or outside the polygon from the information stored in the silhouette line buffer. . In this case, the contour line information is stored in the silhouette line buffer in the light source system coordinates in the first pass, and the drawing points interpolated by the above-described expression (1) or (2) in the viewpoint system coordinate values in the second pass. Conversion to coordinate values is performed, and verification is performed using the contour line information of the information buffer that constitutes the silhouette line buffer obtained in the first pass. The sampling point indicates a drawing coordinate value converted into a light source system coordinate in shadow processing. Sampling points are substituted into the linear equations obtained from the contour line information, and the values and the sampling points are subtracted, and the inside / outside determination of the sampling points is performed with a code based on the flags on the left and right sides. The procedure is as follows.
1. If the sampling point is outside the outline (polygon) stored in all the information buffers, and the z value of the BK buffer is compared with the z value of the sampling point, the sampling point is closer to the light source or viewpoint Outside the region (irradiation point in the case of shadow determination), on the other hand, if the sampling point is far from the BK buffer, the determination ends as the back (shadow in the case of shadow determination).
2. If the sampling point is in the area of any information buffer outline and the comparison result of the z value is far away, it is behind (shadow).
3. If the sampling point is inside a certain polygon, but close to the light source and out of the area for all the stored information in the higher-order buffer, it is out of the area (irradiation point).

Table 2 is a relationship table between sampling points and contour lines. As an example, polygon inside / outside determination is performed by substituting a sampling point into a linear expression obtained from outline information, and the difference between the result value and the sampling point is determined by a sign. In Table 2, Xj and Yj are coordinate values obtained by substituting sampling points (Xi, Yi) into the equations (1) and (2), respectively. Inside Right and Left represent the right and left sides of the polygon, respectively.

  Shadow silhouette line antialiasing, polygon boundary edge antialiasing

From

It can be realized by the same process. The difference is that the former is the determination of the inside / outside region of the polygon at the interpolation point, while the latter is the luminance synthesis proportional to the area of each polygon in the grid.

  The shadow is a two-pass method, whereas the Boundary Edge Anti-aliasing is a one-pass method, and outline line information is stored at the time of viewpoint system coordinate drawing, and brightness synthesis is performed for each polygon drawing or after drawing. Each is different. These anti-aliasing circuits can obtain a high-quality image by combining with a polygon interpolation or luminance calculation circuit as a basic function of a computer graphics processor or an image processing apparatus.

  According to the present invention, it is possible to draw an image having a light reflection effect with a realistic feeling close to nature in real time.

  The technique of the present invention is implemented in an LSI, a programmable logic circuit or the like or in the form of IP (Intelligent Property), and is applied to a computer graphics processor or an image processing apparatus.

  FIG. 1 shows an example of intersection between a grid and an outline line according to the present invention. (1) in FIG.

This corresponds to the relationship of one term. (2) and (3) are respectively

2 and 2-2. A broken line in the figure indicates an overlap with another polygon side.

2-3 and 2-4 also have the relationship of (2) and (3). (4) shows the relationship where three outlines intersect. (5) and (6) are

These correspond to 3-1 and 3-2. (7)

No. 3-3. (8) and (9) are

4-1 and 4-2. (10) and (11) are

4-4 and 4-5. In addition, in the present invention, when a plurality of objects shown in Buf1 in FIG. 1 are different (three types are shown in the figure, each indicated by a solid line, a broken line, and a chain line) and outline lines intersect, Buf2 is a polygon that is a solid line In Buf2, the broken line polygon outline is stored in Buf2, and the information of the broken line polygon outline is stored in Buf4. In the figure, Buf means an information buffer and its extension buffer. In one information buffer and its extended buffer, up to three sets of polygon outline information with the same identifier are stored as an example.

  FIG. 2 shows an example of a grid position through which an outline line according to the present invention passes. When a contour line indicated by a solid line passes through the grid, in the conventional DDA that performs rounding correction, the black circle grid is the contour line pixel. However, as shown in FIG. 2 (1), the outer tightening passes through the broken-line grid. Therefore, in the present invention, in the case of (1) in the figure, each of the black circle and the dashed circle is a target pixel (outline crossing grid). On the other hand, in (2) in the figure, the outline lines do not intersect with respect to the right two pixels (black circles), but according to rounding correction, the black circle pixels one level above are effective. In the present invention, the silhouette line buffer (planar buffer) does not set the flag for the black circle grid of the right two pixels through which the outline does not pass, but sets the flag for the lower stage (dotted line circle). Further, (3) in the figure shows an example in which all pixel points (black circles) indicated by the DDA and a grid (broken line circles) through which the outline passes are provided. In the silhouette line buffer, a flag is set only for the outline line intersecting pixel point (dotted line circle), and the black circle grid through which the outline line does not pass is not recognized as a silhouette line.

FIG. 3 shows a circuit for storing silhouette line information according to the present invention. The polygon vertex information is sequentially given to the polygon outline interpolation circuit 30. The interpolation circuit 30 linearly interpolates the vertex information along the outline connecting the vertices. The interpolation circuit 30 outputs x and y to the span interpolation circuit 31 and the multiplexers 32 and 33 based on the expression (1) or (2) regarding the x and y coordinate values among the vertex coordinate values. The z-coordinate values not described in the equations (1) and (2) are obtained by the interpolation circuit 30 using the long-axis coordinate of x and y as a linear equation substitution value. That is, in the linear formula of the z coordinate, when the x coordinate is the long axis, the y coordinate of the formula (1) is expressed as the z coordinate value. In a system that generates a shadow silhouette line, x, y, and z coordinate values are defined by a light source system (a coordinate system in which the light source is regarded as the projection center). The interpolation circuit 30 has a circuit configuration in which two circuits or one circuit are switched alternately in order to obtain parallel interpolation values on the left and right sides of the polygon simultaneously in parallel or alternately. The left and right outline interpolation values are given to the next-stage span interpolation circuit 31, and the span interpolation circuit 31 further interpolates in the span direction using the coordinate values on the left and right outlines as end points to obtain coordinate values on the polygon horizontal axis. .
The contour line interpolation circuit 30 outputs not only the integer coordinate values but also the slopes of the right and left side contour lines, decimal point coordinate values, left and right side information, and long and short axis information in accordance with the progress of the interpolation calculation. The z values obtained by the interpolation circuits 30 and 31 are added to the z value comparison circuit 36 through the multiplexer 33, respectively. The multiplexer 33 switches the z value at each output time of the interpolation circuits 30 and 31 and inputs the z value to the z value comparison circuit 36. This z value is called the source z value. The z value comparison circuit 36 compares the source z value and the z value stored in the information buffer 37 (referred to as a destination z value). If the destination z value is close to the light source, it is left in the information buffer 37, and if it is far away, it is replaced with the source z value.

The address control circuit 38 generates a z-value read address from the information buffer. The x and y coordinate values output from the interpolation circuits 30 and 31 are selected by the multiplexer 32 and then input to the address generator 34 and the plane buffer 35. The x and y coordinate values are directly added to the two-dimensional array plane buffer 35 including all the pixels, but the information buffer 37 receives a remainder value obtained by polynomially dividing the x and y coordinate values by the address generator 34. After being converted into a physical address by the address control circuit 38, it is given as an address.
The outline line flag is read from the plane buffer 35. If the flag is set, the information buffer indicated by the address from the address control circuit 38 using the x and y addresses and the z value stored in the extension buffer are respectively read. These z values are used as a destination z value and compared with the source z value by the comparison circuit 36. The comparison result is hidden in the address control circuit 38 by detecting an empty buffer and comparing z values together with information from the information buffer 37 (such as a flag indicating a buffer in use) and information from the outline interpolation circuit 30. This is used to replace the outline information generated by deletion by the erasing process.
From the above, only the outline line information that becomes a silhouette line is stored in the plane buffer 35 for the outline line flag and the information buffer 37 when all the interpolations are completed.

  FIG. 4 is an overall view of silhouette line processing of the present invention (second pass in the case of a shadow). In the outline 40 and span 41 interpolation circuit, the interpolation values at all points inside the polygon of the information defined in the polygon vertex are obtained. In the case of shadow processing, the coordinate values are interpolated by viewpoint coordinates, and are converted into light source system coordinate values by the coordinate conversion circuit 42 (the circuit 42 is not used in antialiasing of the viewpoint coordinate system silhouette run). When the light source system coordinate value is defined as the vertex information, the coordinate conversion circuit 42 may be omitted. On the other hand, the interpolated vertex definition information other than the coordinate value is added to the shader 43 for each interpolation, and the shader determines the luminance of the interpolation point from these interpolation values. The light source system coordinate values output from the coordinate conversion circuit 42 are given to the silhouette line buffer 44. The silhouette line buffer is composed of a plane buffer (35 in FIG. 1) and an information buffer (37 in FIG. 1) storing an outline line flag and its extended buffer. The coordinate value converted by the coordinate conversion circuit 42 and the indirect address obtained from the coordinate value are used to read the plane buffer in the silhouette line buffer 44. If there is no outline line flag, no silhouette processing is performed. When there is an outline flag, the converted coordinate value is obtained from the interpolation coordinate value and the stored outline information through the address generator 34 shown in FIG. The boundary area determination circuit 45 determines whether the interpolated coordinate value is located inside or outside the polygon outline that intersects the grid using the grid area information. In the case of the inside of the polygon, the z value is compared, and it is also determined whether or not it is located farther than the polygon. As a result of the determination, if it is determined that the pixel is located behind the polygon, the interpolation point is regarded as a shadow, and a predetermined value is given to the scaler circuit 46 in order to attenuate the luminance obtained by the shader 43, and the luminance is obtained by multiplication. The result is stored in the image memory 47 as the luminance of the pixel.

FIG. 5 shows a detailed view of the boundary region determination circuit 45 of the present invention shown in FIG. The interpolation interpolation coordinate value of the polygon is converted into the light source system coordinate value by the coordinate conversion circuit 42 in FIG. 4 and xl, yl, and xl are added to the plane buffer of the silhouette line buffer 50 as xl, yl, and zl in FIG. The flag F is read and output to the AND circuit 54 to determine whether the interpolation point is an outline grid. On the other hand, the zl value is compared with the z value in the information buffer by the z comparison circuit 53. The address generation of the information buffer from the coordinate value xlyl is performed by the address generator 34 in FIG. 3, and the outline information is read when the interpolation point is an outline grid. Among the outline information, the z value (zd in the figure) has the number of outline lines, and is sequentially compared with zl. The comparison result is given to the AND circuit 54 via the S bus. Of the contour line information, information such as the slope of the contour line and the decimal point value is added to the straight line generator 51 by the E bus, and the values xiii obtained by substituting xl and yl into the linear equation, and xl and yl are obtained. The sign determination circuit 52 makes a difference, and determines whether the interpolation points xl and yl are inside or outside the polygon from the sign and the left and right side information. The determination value D is given to the AND circuit 54, and it is determined whether the interpolation point is close to the polygon light source or behind the polygon in the grid from the comparison result of the z value and the condition of the outline line flag.
In a grid where a plurality of contour lines intersect, the contour line information stored in the information buffer 50 is read sequentially or simultaneously, and the z comparator 53 implements sequential or multiple comparators and compares them simultaneously. In the relationship between the read comparison result of zd and zl and the inside / outside value of the contour line corresponding to the polygon, when the interpolation point is near the light source, the interpolation point is Possible irradiation point. On the other hand, if it is behind, there is a possibility of an irradiation point only when it is located outside the polygon. When the interpolated point is located behind the polygon and inside the polygon, it becomes a shadow, and determination processing is unnecessary even if more contour lines are stored. As long as it is determined that there is a possibility, the stored outline information is determined sequentially or simultaneously under the above conditions, and when the position of the interpolation point is outside or inside all polygons, the polygon is closer to the light source. When it is determined that the AND circuit 54 satisfies the irradiation condition. In the case of an irradiation point, the scale value given to the scaler 46 in FIG. 4 from the boundary region determination circuit by the IN / OUT signal is 1, and the luminance is not attenuated.

  FIG. 6 shows a buffer structure for storing outline information of the present invention. The plane buffer 60 has a two-dimensional array of x and y, and stores a 1-bit flag in an outline line passing pixel (grid). In the shadow processing, when the polygon interpolation point is transformed into the coordinate system of the first pass in the process of drawing each polygon in the second pass and xl and yl are obtained, the plane buffer 60 is read at this address. When the outline flag is set at the readout point (black dot in the figure), the address xl and yl at that point is converted by the address generator 61 using xl and yl as input data to convert the remainder value. It will be a later address. As the address of the information buffer 62, the remainder value ai reads out the outline information from the buffer (the word of the information buffer and its extension buffer) in which the effective bit is stored at the address position. The information buffer 62 may be a one-dimensional memory. The word structure 63 corresponding to each address of this information buffer for storing outline information comprises three blocks, and outline information shown in the figure is stored in one block. An example of the bit length is shown in parentheses in the outline information. These pieces of information are obtained in the first pass in the shadow processing. In contour line drawing in the viewpoint coordinate system, outline line information in the viewpoint coordinate system is stored. The valid bit indicates that the corresponding intra-block information is valid. The positional relationship between the information buffer and the expansion buffer may be performed by further generating a link address starting from the address ai. However, when the memory access time is given the highest priority, each information buffer is the same. The address may be shared. In this case, the number of word bits per address of the information buffer is increased. In the latter case, since the memory cost increases, it is necessary to terminate the expansion number to an appropriate number (4 or 5). Although not shown in the figure, the information buffer includes one set of background buffers (one for the ai address) corresponding to the address of each information buffer. When the interpolation point of the polygon is an outline crossing grid and the address ai of the information buffer is determined, valid outline line information is read from the information buffer, and this is given to the boundary area determination circuit of FIG.

  Said

From

Is related to the case where the polygon outline information is used for shadow determination, but the silhouette line anti-aliasing process does not determine the position inside or outside the shadow polygon, but the brightness corresponding to each polygon area included in the grid in the viewpoint system coordinates. It differs in that it becomes the distribution of. Also, unlike the generation of a two-pass shadow, the contour line information is stored in the silhouette line buffer when drawing in the viewpoint coordinate system. Further, luminance or color information of each polygon is additionally stored as outline data in the word of the information buffer in FIG. That is, in anti-aliasing, the same circuit as that in FIG. 3-5 except that there is no drawing in the light source system coordinates, the boundary determination circuit 45 in FIG. 4 replaces the area calculation circuit, and the process of performing luminance synthesis from area calculation. It can be configured with a circuit. Luminance composition for the area ratio can be performed for each pixel in the viewpoint coordinate system drawing or after drawing in the method of storing outline information in the information buffer for each polygon in the present invention.

  By mounting the circuit of the present invention as an IP (Intelligent Property) or a graphics processor LSI chip, real-time drawing can be performed in a system such as video production or CG game.

  “Grid-inner-outline crossing diagram related to the present invention”   “Outer Line Intersection Grid for the Present Invention”   "Silhouette line information storage circuit of the present invention"   "Silhouette line processing circuit of the present invention   "Boundary judgment circuit of the present invention"   “Outer Line Storage Buffer Structure of the Present Invention”

Explanation of symbols

FIG.
(1)-(11) Outer grid line crossing example Buf1-4 Outer line and information buffer storage example FIG.
(1)-(3) Outline line grid example Fig. 3
30 outline interpolation circuit 31 span interpolation circuit 32 multiplexer 33 multiplexer 34 address generator 35 plane buffer 36 z-value comparator 37 information buffer 38 address control circuit FIG.
40 outline interpolation circuit 41 span interpolation circuit 42 coordinate conversion circuit 43 shader 44 silhouette line buffer 45 scaler 46 boundary region determination circuit 47 image memory FIG.
50 silhouette line buffer 51 straight line generation circuit 52 sign determination circuit 53 z value comparator 54 AND circuit diagram 6
60 silhouette line plane buffer 61 address generator 62 information buffer 63 information buffer word configuration diagram

Claims (8)

  In the anti-aliasing technology for polygons to be silhouette lines, means for storing pixel points on the outline line connecting the vertex coordinates of the polygons as a outline line flag in a two-dimensional array buffer (hereinafter referred to as a plane buffer), and pixels in a square area (Hereinafter referred to as a grid), and a buffer (hereinafter referred to as an information buffer) comprising a plurality of one-dimensional arrays is provided, and intersection information (hereinafter referred to as outline information) when the outline passes through the grid, Means for storing in the information buffer; the plane buffer for addressing the coordinate value of the contour line; and the information buffer for addressing by an indirect address obtained from the contour line coordinate value; and each word of the information buffer A means with a capacity to store at least three outline information every time If the polygon side is shared with other polygon sides and the postscript outline matches the foreword outline stored in the buffer, the prelude outline information is deleted from the corresponding information buffer and the postscript outline information In the step of painting inside the polygon performed after the outline line interpolation, the plane buffer is read out using the polygon interpolation coordinate value as an address, and if there is an outline flag, the corresponding information buffer The contour line information is read out from each of them, and the distance information from the projection center stored as one of the contour line information is compared with the distance of the interpolation point, and is located farther than the interpolation point. In this case, after each polygon is drawn using each of the means for deleting the corresponding outline information stored in the information buffer, the plane bar is displayed. Polygon silhouette line antialiasing circuit flags on outline of the silhouette line and the information buffer that stores outline information corresponding to the flag points to file. 2. The circuit according to claim 1, wherein an effective flag indicating that the outline information is valid, an inclination of the outline intersecting with the grid, an intersection axis and an intersection coordinate value, and an outline line branched from the y-axis minimum vertex coordinate point as a base point. Means for storing the values indicating the left and right sides, the long axis, the x-axis step direction, the distance from the projection center to the grid intersection, and the order value to be updated for each polygon as outline information, and for each word in the information buffer Means for storing and updating a maximum distance value from the projection center as an initial value in the background buffer, while storing and updating at a distance closest to the projection center in interpolation interpolation inside the polygon, When the contour line stored in the information buffer and the postscript contour line share a polygon edge, the contour line is regarded as not a silhouette line, and the corresponding buffer in the information buffer is used. A polygon silhouette line anti-aliasing circuit having means for resetting the valid flag stored in the file and means for resetting the outline flag of the planar buffer when the valid flags of all information buffers are reset . 3. The circuit according to claim 1, wherein, as means for performing anti-aliasing of shadows, polygon interpolation is performed when a polygon is drawn in the light source coordinate system in the first pass and is drawn again in the viewpoint coordinate system as the second pass. Each time, the plane buffer is read using the coordinate value obtained by converting the interpolation point from the viewpoint coordinate to the light source coordinate system, and if there is an outline line flag, the outline line information is read from the information buffer, and the outline line information and the light source system coordinates are read out. A value is used to determine whether the interpolation point is located inside or outside the polygon in the grid, and if inside the polygon, the distance from the projection center is further compared, and the converted coordinate point is stored in the information buffer. If it is determined that the information is far away from the distance of the information, a means for making a shadow, and if the interpolation point is outside the polygon, whether or not contour line information is stored If the contour line information is stored, the same determination as described above is performed. If it is determined to be a shadow, the interpolation process of the second pass is terminated as a shadow at that stage, and all stored contours are determined. When it is determined that the interpolation points are outside the region or are all closer to the projection center within the region with respect to the line information, each means includes the respective insertion points as the irradiation points. Polygon / silhouette line antialiasing circuit including polygon inside / outside detection circuit. 3. The circuit according to claim 1, wherein an outline line flag obtained by interpolating a polygon in a viewpoint coordinate system is stored in the plane buffer as means for performing anti-aliasing of a polygon / silhouette line drawn in the viewpoint coordinate system from information stored in the buffer. Means for storing outline line information in the information buffer; means for adding color information of a polygon having the outline as outline line information; and adding a background color as an initial value to the background buffer, In the case of internal interpolation, when the interpolation point is closer to the background buffer than the distance from the viewpoint stored in the background buffer, the background buffer contains the distance and the interpolation polygon. The means for making color information and the plane buffer are read for each interpolation point inside the polygon, and the interpolation point is determined to be a silhouette line. In this case, the contour line information read from the information buffer is used to determine the area occupied by each polygon when the grid is used as the projection plane, and the respective areas are determined according to the respective areas. Polygon / silhouette line antialiasing circuit that determines the brightness of the grid that is the silhouette line from each of the means for proportionally distributing the colors of the polygon. 2. The circuit according to claim 1, wherein as a means for determining a grid at which the outer lines intersect, a real value obtained from a linear equation is used as a coordinate value without rounding correction on the short axis side of the x and y coordinates of the straight line generator. And the grid coordinates indicated by the integer value of the real value, the grid intersection coordinates indicated by the decimal point value, and the slope and direction of the straight line expression, detect all grids where the straight lines intersect, A polygon / silhouette line anti-aliasing circuit including an outline cross grid determination circuit for storing a flag in the plane buffer as an outline cross grid and storing outline information in an information buffer. 3. The circuit according to claim 1 or 2, wherein an identifier is provided for a drawn object with respect to means for storing contour line information, and when the object identifier changes during interpolation of the contour line, the object is a storage object until then. Even if the storage area remains in the information buffer word, if the object identifier is the same as the means for storing the outline information by switching to the extended information buffer and the order value for each polygon is different, the same object The outline information is read from each of the information buffers having the identifiers, compared with the outline being interpolated, and when a common outline is detected, the valid flag of the outline information in the corresponding buffer is reset. At the same time, when an empty area is generated in the buffer due to the reset, a process for filling the empty area by shifting the outline information in the information buffer or between the buffers for each object identifier is performed. If it is determined that the contour line being interpolated does not share any of the stored edges, the contour line information is sequentially stored in the information buffer. If the number of intersections exceeds the storage area, the information buffer is expanded. Polygon / silhouette line anti-aliasing circuit with each storage means to store.   5. The circuit according to claim 1, wherein a normal line, a light source incident angle, etc. are defined in the polygon vertex as means for storing the color information of the polygon, and the luminance is determined only after the luminance calculation circuit. Are transmitted from the polygon interpolation circuit to the luminance calculation circuit, and the polygon interpolation coordinate value, color information, and the sequence value are output in synchronization from the luminance calculation circuit, and the interpolation interpolation is performed. Using the x and y coordinate values of the points as addresses, the plane buffer is read, and when there is an outline flag, polygon outline information matching the sequence value output from the luminance calculation circuit is detected from the information buffer. A polygon silhouette line antialiasing circuit having means for additionally storing the color information from the luminance calculation circuit in the outline information of the corresponding information buffer   A computer graphics image apparatus using the polygon silhouette line anti-aliasing circuit according to claim 1.

Images