JP2720818B2 - 3D polygon drawing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional polygon drawing method for drawing a polygon in a three-dimensional drawing system for performing three-dimensional drawing (display) on a two-dimensional display area, and more particularly to a hidden surface. The present invention relates to a three-dimensional polygon drawing method for performing an erasing process. In the specification of the present application, description will be made on the assumption that the polygon to be drawn in the three-dimensional polygon drawing method is a trapezoid. However, a complex polygon other than a trapezoid can be processed as a set of trapezoids by trapezoidal division processing or trapezoidal approximation processing, so that the polygon to be drawn in the three-dimensional polygon drawing method of the present invention is limited to a trapezoid. It goes without saying that it is not something that can be done.

[0002]

2. Description of the Related Art When a hidden surface erasing process is performed in a conventional three-dimensional polygon drawing method, depth values (depth values; hereinafter, referred to as "z values") of all pixels in a display area are stored. A z-value storage means (z-buffer) is provided to perform the following processing (see FIG. 6).

A pixel located at an intersection of each scan line with a left side of a polygon to be rendered at the present time (hereinafter, referred to as a “current rendering polygon”) (hereinafter, each scan line of the current rendering polygon) (Referred to as “left end pixel”) (za in FIG. 6) and a pixel located at the intersection of the right side of the current drawing polygon and each scan line (hereinafter, each scan line of the current drawing polygon) "Right end pixel")
(Zb in FIG. 6) is obtained for all scan lines where the current drawing polygon exists.

The z value of each pixel included in the current drawing polygon is obtained by the following equation based on the z values (za and zb in FIG. 6) obtained by:
Note that, as shown in FIG. 6, the x coordinate value of the pixel to be calculated is xc, and the calculated z value is zc. zc = za + {(zb−za) / (xb−xa)} ×
(Xc-xa)

And the z value of each pixel in the z value storage means (z at the same coordinate position as the coordinate position of each pixel)
(Z value in the value storage means).

The comparison result is compared with the hidden surface condition, and the hidden surface erasing process is performed based on the comparison result.
That is, the z value of each pixel of the current drawing polygon is z
In the case where the position is deeper than the z value of each pixel in the value storage means, the current drawing polygon is not drawn for that pixel (when both z values are equal, the current drawing polygon is not drawn). Whether or not to perform drawing depends on the hidden surface condition).

[0007]

In the above-described conventional three-dimensional polygon drawing method, the creation (calculation) of the z value relating to the current drawing polygon for the hidden surface erasing process is performed in pixel units. As a mode of the erroneous hidden surface removal processing in a portion where a plurality of polygons are close to each other in the depth direction, the current drawing polygon may be set to another pixel in one pixel group adjacent in the scan line direction of the display area. It is determined that it is located above / below the polygon, and is drawn / erased. However, for the other pixels on both sides of the one pixel, it is determined that the current drawing polygon is located below / above, and is erased / drawn. " Phenomenon may occur.

This is caused by a calculation error when the above-described formula for calculating the z value (zc) is applied to each pixel, and relates to a plurality of polygons having substantially the same z value. This is caused by the calculation error having a different effect on each of the neighboring pixels.

In the conventional three-dimensional polygon drawing method, a drawing in which a plurality of polygons are blurred in a portion close to the depth direction occurs due to the above-described phenomenon occurring in the hidden surface erasing process. There was a problem.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide a three-dimensional polygon capable of reducing blurring in drawing caused by a calculation error in calculating a z value for hidden surface elimination processing. An object of the present invention is to provide a drawing method.

[0011]

According to a three-dimensional polygon drawing method of the present invention, a polygon is drawn in a display area in a three-dimensional polygon drawing method in which a hidden surface is erased in a three-dimensional drawing system to draw a polygon. , A drawing data generating means for generating drawing data including an x-coordinate value, a y-coordinate value and a color value of the current drawing polygon, and a z-value of each of all pixels in the display area at that time. Z-value storage means for storing the z-values of the pixels included in the uppermost polygon, and pixels included in the current drawing polygon are integrated as a pixel set for each number of inclusive pixels in the scan line direction. A pixel set integrating unit in the z-value creating means for setting a representative pixel in the pixel set, and a representative pixel of each pixel set set by the pixel set integrating unit Seeking z value, and the z value calculation section in the z value creation means for setting the z values of all pixels belonging to the pixel set to the same value as z value of the representative pixel, the z
The z value of each pixel stored in the value storage means and the z value
Z-value comparing means for comparing the z-value of each pixel included in the current drawing polygon created by the value creating means on a pixel-by-pixel basis and creating the comparison result, and the comparison created by the z-value comparing means By comparing the result with the hidden surface condition, it is determined whether or not to draw the current drawing polygon for each pixel included in the current drawing polygon. And drawing control means for outputting the created drawing data to the display means and outputting the z value created by the z value creation means to the z value storage means.

[0012]

In the three-dimensional polygon drawing method of the present invention, the display means displays the polygon in the display area, and the drawing data creating means displays the drawing data including the x coordinate value, the y coordinate value, and the color value of the current drawing polygon. And the z-value storage means stores the z-value of the pixel contained in the polygon located at the top at that time as the z-value of each of all the pixels in the display area,
A pixel set integration unit in the value creation unit integrates the pixels included in the current drawing polygon in the scan line direction as a pixel set for each number of comprehensive pixels, sets a representative pixel in each pixel set, The z-value calculator within calculates the z-value of the representative pixel of each pixel set set by the pixel set integrating unit, sets the z-values of all the pixels belonging to the pixel set to the same value as the z-value of the representative pixel, The z value comparing means compares the z value of each pixel stored in the z value storing means with the z value of each pixel included in the current drawing polygon created by the z value creating means on a pixel-by-pixel basis. The comparison result is created, and the drawing control unit compares the comparison result created by the z-value comparison unit with the hidden surface condition, and calculates a calendar for each pixel included in the current drawing polygon. It is determined whether or not the drawing polygon should be drawn. For the pixel determined to be drawn, the drawing data created by the drawing data creation means is output to the display means, and the z-value created by the z-value creation means is output. Output to the z value storage means.

[0013]

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an embodiment of a three-dimensional polygon drawing method according to the present invention.

The three-dimensional polygon drawing method according to the present embodiment includes a drawing data creating means 1, a z value creating means 2, a z value comparing means 3, a drawing controlling means 4, a z value storing means 5, And means 6. Note that the z-value creating means 2
Is configured to include a pixel set integration unit 21 and a z-value calculation unit 22.

FIG. 2 is a flowchart showing the processing of the three-dimensional polygon drawing method according to the present embodiment. This processing includes a drawing data creation step 201, a z value creation step 202, a z value comparison result creation step 203, a hidden surface condition determination step 204, and a z value and color value output step 205.

FIG. 3 is a flowchart showing the detailed processing of the z-value creation step 202. This processing includes an all scan line end determination step 300, a za and zb calculation step 301, a pixel set integration step 302, a representative pixel setting step 303, and a zc calculation step 3
04, an all-pixel z-value setting step 305, and a z-value correction step 306.

FIG. 4 is a diagram for explaining the processing of the z-value creating means 2 in the three-dimensional polygon drawing method of the present embodiment.

FIGS. 5A and 5B are diagrams for explaining variations of the processing of the z-value creating means 2. FIG.

Next, the operation of the three-dimensional polygon drawing method of the embodiment constructed as described above will be described.

The z value storage means 5 stores the z value of each pixel in the display area of the display means 6. As the z value of each pixel in the z value storage means 5, the z value of the pixel included in the polygon located at the highest point at that time is stored. In this embodiment, it is assumed that the larger the z value, the higher the position (shallow position).

In the three-dimensional drawing system to which the present embodiment is applied, when the z value of a pixel constituting the current drawing polygon is larger than the z value of the pixel in the z value storage means 5 at that time. Performs drawing on the pixel, and uses the z value as the z value in the new z value storage means 5. That is, it is assumed that the hidden surface condition is set such that “the current drawing polygon is not drawn when the z value is smaller than or equal to the previously drawn polygon”.

The drawing data creating means 1 creates drawing data including the x coordinate value, the y coordinate value, and the color value of each pixel included in the current drawing polygon (step 20).
1). The processing for creating such drawing data is the same as the processing in the related art.

The z-value creating means 2 calculates the z value of each pixel constituting the current drawing polygon as shown in the following.
Create values (see FIGS. 3 and 4). The following processing is repeated for each scan line where the current drawing polygon exists (see step 300).

The z-value calculator 22 calculates the z-value (za in FIG. 4) of a pixel (left-end pixel) located at the intersection of the left side of the current drawing polygon and the scan line to be processed.
And the z value (zb in FIG. 4) of a pixel (right end pixel) located at the intersection of the right side of the current drawing polygon and the scan line (step 301). Note that such z-value calculation processing is the same as the processing in the related art.

The pixel set integration unit 21 determines, for a region where the current drawing polygon exists, a pixel of the scan line from the pixel having the x-coordinate value of 0 for every comprehensive pixel number (arbitrary pixel number given in advance). A set is extracted and integrated (step 302). That is, each pixel set in the scan line direction of the current drawing polygon is obtained by dividing the pixel set by the number of comprehensive pixels based on the origin of the display area. Here, a pixel set including the left end pixel is referred to as a “left end pixel set”.
The pixel set including the rightmost pixel is referred to as “rightmost pixel set”, and the pixel set existing between the leftmost pixel set and the rightmost pixel set is referred to as “intermediate pixel set”.

The pixel set integration unit 21 sets the representative pixel of each pixel set to the leftmost pixel of each pixel set (step 303).

The z-value calculating unit 22 calculates the z-value of the representative pixel of each intermediate pixel set based on the following expression (referred to as “intermediate pixel z-value calculation expression”) (Step 304). Note that the x coordinate value of the representative pixel of the set of intermediate pixels to be calculated is xc, the calculated z value is zc, and the x coordinate value of the representative pixel of the leftmost pixel set is x
a ', and the x coordinate value of the representative pixel of the rightmost pixel set is xb'. zc = za + {(zb−za) / (xb′−xa ′)}
× (xc−xa ′)

Further, the z-value calculator 22 sets the z-values of all the pixels belonging to each pixel set to the same values as the z-values of the representative pixels of each pixel set (step 305). Here, it is assumed that the z value of the representative pixel of the leftmost pixel set is regarded as za which is the z value of the leftmost pixel, and the z value of the representative pixel of the rightmost pixel set is regarded as za which is the z value of the rightmost pixel. As a result, the z-values of all the pixels belonging to the leftmost pixel set are set to the same value as the z-values of the leftmost pixel, and the z-values of all the pixels belonging to the rightmost pixel set are z values of the rightmost pixel.
The z value of all the pixels belonging to the intermediate pixel set is set to the same value as the z value of the representative pixel of the intermediate pixel set obtained in step 304.

Further, the z-value calculating unit 22 determines the z-value of a pixel existing on the left side of the leftmost pixel in the leftmost pixel set and a pixel present on the right side of the rightmost pixel in the rightmost pixel set as “polygon exists. To "information indicating not to be performed" (here, 0) (step 306).

Incidentally, the value of the number of comprehensive pixels is empirically determined as follows:
For example, as shown in FIG. 4, a numerical value "5" can be considered.

The z-value comparing means 3 stores the z-value (referred to as zs) of each pixel included in the current drawing polygon created as described above by the z-value creating means 2 and the z-value storing means 5. Is compared with the z value (let it be zd) of the relevant pixel, and the comparison results (“zs> zd”, “z
s = zd ”or“ zs <zd ”) is created (step 203).

The drawing control means 4 checks the comparison result of each pixel created by the z-value comparing means 3 with the hidden surface condition, and determines whether or not to draw a current drawing polygon for each pixel. (Step 204).

The drawing control means 4 determines only those pixels (the pixels whose comparison result is "zs>zd") that have determined in step 204 that the current drawing polygon should be drawn in light of the hidden surface condition. The z value created in step 202 is output to the z value storage means 5, and the drawing data (color value) created in step 201 is output to the display means 6 (step 205).

The z value storage means 5 stores the z value received in step 205 as a new z value. The display unit 6 draws (displays) the current drawing polygon in the display area based on the drawing data received in step 205.
I do.

In the above description of the operation, the creation of the z value (see step 202 and FIG. 3 in FIG. 2) and the output of the z value and the color value (in FIG. And the like (see step 205).
However, the operation of the present embodiment and the operation of the present invention are not limited to such an embodiment. For each pixel (for each pixel), creation of a z-value and output (output) of a z-value and a color value are performed. It is needless to say that it is also possible to carry out (including recognition of not performing).

As described above, when the z value of each pixel is created (calculated) in a pixel set unit, the z value calculation accuracy may be lower than in the case of creating the z value in a pixel unit. As a mode of the erroneous hidden surface erasing process, “for one pixel in a pixel group adjacent in the scan line direction of the display area, it is determined that the current drawing polygon is positioned above / below another polygon, and is drawn / erased. However, with respect to other pixels on both sides of the one pixel, the current drawing polygon is determined to be positioned at the bottom / top, and is erased / drawn. " Therefore, there is less possibility that a drawing in which a plurality of polygons are blurred in a portion adjacent in the depth direction will occur.

It is to be noted that the number of comprehensive pixels is not set in advance as an eigenvalue of the system (a three-dimensional rendering system to which the three-dimensional polygon rendering method of this embodiment is applied), but the z value is externally set by a user or the like. It is also possible to make it possible to designate it to the creation means 2. Accordingly, it is possible to set an appropriate number of comprehensive pixels according to a drawing target. For example, it is possible to set an appropriate number of comprehensive pixels in consideration of both high accuracy of z-value calculation and reduction of blur. Becomes

By the way, with respect to the processing of the z-value creating means 2 (integration of pixel sets, handling of setting of representative pixels, etc.), the following variations are conceivable (FIGS. 5A and 5B). reference).

As shown in FIG. 5A, in each pixel set, pixels other than the left end (the right end pixel and the center pixel) are set as representative pixels.

As shown in FIG. 5B, a pixel set is obtained by dividing the left end point pixel by the number of inclusive pixels. That is, a pixel set for each comprehensive pixel number in each scan line is integrated based on the left end pixel. In this case, the representative pixel of each pixel group is set to the leftmost pixel in each pixel group. Also, regarding the left end pixel set, FIG.
The correction in the middle step 306 becomes unnecessary.

[0042]

As described above, according to the present invention, when a polygon is drawn by the three-dimensional drawing system, the creation (calculation) of the z value used in the hidden surface removal processing can be performed by an arbitrary number of pixels (inclusive). Performing in units of (number of pixels) has the effect of reducing blurring in drawing due to a calculation error in calculating the z value.

By making it possible for a user or the like to specify the number of comprehensive pixels from the outside, it is possible to appropriately achieve the above-described effects in accordance with the drawing object. For example, it is possible to set an appropriate number of comprehensive pixels by considering both the high calculation accuracy of the z value and the reduction in blur.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a three-dimensional polygon drawing method according to the present invention.

FIG. 2 is a flowchart showing processing of the three-dimensional polygon drawing method shown in FIG.

FIG. 3 is a flowchart showing a detailed process of a z-value creating step in FIG. 2;

FIG. 4 is a diagram for explaining processing of a z-value creating unit in FIG. 1;

FIG. 5 is a diagram for explaining a variation of processing of a z-value creating unit in FIG. 1;

FIG. 6 is a diagram for explaining z-value creation processing in a conventional three-dimensional polygon drawing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drawing data creation means 2 z value creation means 3 z value comparison means 4 drawing control means 5 z value storage means 6 display means 21 pixel set integration part 22 z value calculation part

Claims (6)

(57) [Claims] 1. A three-dimensional polygon drawing method for drawing a polygon by performing hidden surface elimination processing in a three-dimensional drawing system, a display means for displaying a polygon in a display area, and an x-coordinate value of a current drawing polygon , Drawing data creation means for creating drawing data including y-coordinate values and color values, and z-values of pixels contained in the uppermost polygon at that time as z-values of all pixels in the display area And z-value storage means for integrating pixels included in the current drawing polygon as a pixel set for each number of pixels in the scan line direction and setting a representative pixel in each pixel set. And a z-value of a representative pixel of each pixel set set by the pixel-set integrating unit. A z-value calculator within the z-value generator for setting the z-value of the pixel to the same value as the z-value of the representative pixel; and a z-value of each pixel stored in the z-value storage and the z-value generator. A z-value comparing means for comparing the z-value of each pixel included in the current drawing polygon created in step 2 with a pixel unit to create a comparison result, and comparing the comparison result created by the z-value comparing means with the z-value It is determined whether or not the current drawing polygon should be drawn for each pixel included in the current drawing polygon by checking the surface condition, and the drawing data generating means generates the pixel determined to be drawn. A three-dimensional polygon drawing method, comprising: drawing control means for outputting drawing data to the display means and outputting the z value created by the z value creation means to the z value storage means. . 2. A pixel set integration unit that integrates pixel sets for each number of comprehensive pixels in each scan line with reference to the origin of the display area, and sets a representative pixel to the leftmost pixel of the pixel set. Is calculated based on the intermediate pixel set z value calculation formula, and the z value of the pixel existing on the left side of the left end pixel in the left end pixel set and the z value of the representative pixel on the right side of the right end pixel in the right end pixel set And a z-value calculator for correcting the z-value of the pixel to be converted into information indicating that no polygon exists.
2. The three-dimensional polygon drawing method according to claim 1, further comprising a value creating unit. 3. The three-dimensional polygon according to claim 2, further comprising a pixel set integration unit that sets the representative pixel to one of a right end pixel and a center pixel instead of the left end pixel of the pixel set. Drawing method. 4. A pixel set integration unit that integrates pixel sets for each of the number of comprehensive pixels in each scan line with reference to the left end pixel, and sets a representative pixel to the left end pixel of the pixel set. The z value of the representative pixel is calculated based on the intermediate pixel set z value calculation formula, and the z value of the pixel located on the right side of the right end pixel in the right end pixel set is corrected to information indicating that there is no polygon. 2. The three-dimensional polygon drawing method according to claim 1, further comprising a z-value creating unit including a value calculating unit. 5. The three-dimensional polygon drawing method according to claim 1, wherein the number of comprehensive pixels is five. 6. The three-dimensional polygon drawing method according to claim 1, wherein the number of comprehensive pixels can be designated from outside.