JP4449582B2 - Image generation device - Google Patents

Description

  The present invention relates to an image generation apparatus that improves image generation efficiency.

When generating an image of an opaque object with a polygon whose normal vector is less than 90 degrees and a polygon that is 90 degrees or more as the back polygon, the angle between the normal vector of the polygons constituting the object in the three-dimensional space and the viewpoint is the front polygon. There is known a method of improving the image generation efficiency by storing the depth value and the luminance value of the image in a buffer and omitting the processing of the back polygon. On the other hand, when generating an image of a semi-transparent object, the depth value and luminance value of the back polygon are first stored in the buffer, and then the depth value and luminance value of the front polygon are stored in the buffer and the hidden surface is deleted. A method of generating is known. Here, since the normal vector of the polygon is used for the determination of the front polygon and the back polygon, it is necessary to calculate the normal vector. An image display device that calculates a normal vector and determines a front polygon and a back polygon is disclosed in Patent Document 1 below. The front and back polygons will be described with reference to FIG. FIG. 7 shows an object 700 composed of polygons a to g and a viewpoint 701. As shown in FIG. 7, an angle 704 formed between a line of sight 702 connecting the viewpoint 701 and the polygon a and a normal vector 703 of the polygon a is less than 90 degrees. That is, the polygon a is a front polygon. In addition, an angle 707 formed by a line of sight 705 connecting the viewpoint 701 and the polygon b and a normal vector 706 of the polygon b is 90 degrees or more. That is, the polygon b is a back polygon. In this way, when considering other polygons in the same manner, the polygon f and the polygon g are front polygons, and the polygon c, the polygon d, and the polygon e are back polygons. In this way, it is determined whether the front polygon or the back polygon.
Japanese Patent Laid-Open No. 11-203486 (paragraph 0010, FIG. 1)

  However, as in the technique disclosed in Patent Document 1, calculating a normal vector used for determination of front and back polygons has a problem of increasing the amount of calculation.

  An object of the present invention is to solve the above-described problem, and an object of the present invention is to provide an image generation apparatus capable of determining the front and back of a polygon without calculating the normal vector of the polygon.

In order to achieve the above object, according to the present invention, object information including at least coordinate information in a three-dimensional coordinate of a vertex of an object composed of a plurality of polygons, and a viewpoint and a light source in the three-dimensional coordinate of the object Receiving means for receiving environment information including at least coordinate information; and converting the coordinate information of the vertex of the object and the coordinate information of the light source received by the receiving means into viewpoint coordinates having the viewpoint position as an origin, A first conversion unit that calculates a luminance value of the vertex of the object in the viewpoint coordinates, and converts coordinate information of the vertex of the object converted into the viewpoint coordinates into a perspective coordinate; and Clipping means for performing clipping for determining a drawing range of the object converted into perspective coordinates The dividing the objects clipped by the clipping means into a polygon having three vertices by XYZ coordinate system, divided second conversion for converting a corner of the drawing range determined the polygon into screen coordinates of the origin And a vertex that minimizes the Y coordinate among the vertices of the polygon converted to the screen coordinates by the second conversion means, and one vertex that minimizes the Y coordinate and the other A determination means for determining whether the front polygon or the back polygon is based on an increase in the X coordinate with respect to an increase in the Y coordinate with respect to each vertex; and for the polygon determined as a front polygon by the determination means, Based on the vertex coordinate information, an inner depth value surrounded by the vertexes of the polygon is calculated, and the calculated object is calculated. A calculation detecting means that to calculate the luminance value of the internal surrounded by the vertices of the polygon by interpolating the intensity values of the vertices of the depth value and the luminance value of the table polygon calculated in the previous hexane detecting means An image generation apparatus is provided that includes control means for storing in a storage means.

  The image generation apparatus according to the present invention has the above-described configuration, and can perform front / back determination of a polygon without calculating a normal vector of the polygon.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram showing a configuration of an image generation apparatus according to an embodiment of the present invention. FIG. 2A is a diagram for explaining viewpoint coordinates in the image generation apparatus according to the embodiment of the present invention. FIG. 2B is a diagram for explaining perspective coordinates in the image generating apparatus according to the embodiment of the present invention. FIG. 3 is a diagram for explaining screen coordinates in the image generating apparatus according to the embodiment of the present invention. FIG. 4 is a diagram showing polygons converted into screen coordinates in the image generating apparatus according to the embodiment of the present invention. FIG. 5 is a flowchart for explaining calculation of polygon parameters in the image generating apparatus according to the embodiment of the present invention. FIG. 6 is a diagram showing an intermediate state between the front polygon and the back polygon in the image generating apparatus according to the embodiment of the present invention.

  First, the configuration of an image generation apparatus according to an embodiment of the present invention will be described with reference to FIG. The image generation apparatus 100 includes a scene data receiving unit 101, a vertex processing unit 102, a pixel processing unit 103, a storage unit 104, and an image output unit 105. The scene data receiving unit 101 receives object information including at least coordinate information in the three-dimensional coordinates of the vertex of an object composed of a plurality of polygons, and environment information including at least coordinate information in the three-dimensional coordinates of the viewpoint and the light source for the object. To do. The scene data in FIG. 1 refers to the object information and environment information described above. Here, the object information may include information representing the color of the object in addition to the coordinate information on the three-dimensional coordinates of the vertex of the object. In addition to the coordinate information of the viewpoint and the light source in the three-dimensional coordinates, the environment information may include information such as the viewpoint direction and field of view, and information such as the light source direction, color, and type. The scene data receiving unit 101 passes the received information to the vertex processing unit 102.

  The vertex processing unit 102 converts the received coordinate information of the vertex of the object and the coordinate information of the light source into viewpoint coordinates having the viewpoint position as the origin, calculates the luminance value of the vertex of the object in the viewpoint coordinates, and sets the viewpoint coordinates. The coordinate information of the vertex of the converted object is further converted into perspective coordinates. Here, the vertex processing unit 102 includes four vertex processing units 0 to 3, but the number is not limited to four and may be one. Further, the luminance value of the vertex of the object is obtained by a conventional method based on the color and position of the light source. Here, the viewpoint coordinates and the perspective coordinates described above will be described with reference to FIGS. 2 (a) and 2 (b). As shown in FIG. 2A, the viewpoint coordinates are coordinates in a coordinate system in which the viewpoint O is the origin and the direction of the line of sight is the Z axis. The field of view at the viewpoint O is a range surrounded by the straight line OAE, the straight line OBF, the straight line OCG, and the straight line ODH with the viewpoint O as a base point. The object is represented by coordinate information when the viewpoint O is the origin. Note that an object positioned between the viewpoint O and the rectangle ABCD is not a drawing target, and only an object positioned between the rectangle ABCD and the rectangle EFGH is a drawing target. Further, as shown in FIG. 2B, the perspective coordinates are obtained by setting the center of the rectangle ABCD as the origin O ′.

  The pixel processing unit 103 performs clipping for determining the drawing range of the object converted into the perspective coordinates. Here, the pixel processing unit 103 includes four pixel processing units 0 to 3, but the number is not limited to four and may be one. Clipping refers to masking the drawing range when displaying an image or drawing a figure. The pixel processing unit 103 divides the clipped object into polygons, and converts the divided polygons into screen coordinates with the corner of the determined drawing range as the origin. Here, the screen coordinates will be described with reference to FIG. As shown in FIG. 3, the screen coordinates are a coordinate system in which the origin O ′ of the perspective coordinates in FIG. 2B described above is the corner of a quadrilateral ABCD (hereinafter also referred to as a screen ABCD). In this case, the clipped drawing range is the range of the screen ABCD. Further, the pixel processing unit 103 calculates a polygon parameter for determining whether the polygon converted into the screen coordinates is a front polygon or a back polygon.

  Here, a polygon parameter calculation method will be described with reference to FIGS. FIG. 4 is a diagram showing a polygon converted into screen coordinates. The vertices of the polygon are V [0], V [1], and V [2], and are composed of x, y, z coordinates and a luminance value i, respectively. Polygon parameters are calculated for a polygon as shown in FIG. A specific polygon parameter calculation flow will be described with reference to FIG. As shown in FIG. 5, the pixel processing unit 103 initializes the vertex number j of the vertex V [j] to be processed to 0, and sets the minimum value ymini and maximum value ymax of the y coordinate at the polygon vertex on the screen coordinates to V. [0] is initialized to y [0], and polygon parameters lv and rv are initialized to 0 (step S501). The pixel processing unit 103 determines whether the value of j is smaller than 3 (step S502).

  In step S502, when the value of j is 3 or more, the process ends. On the other hand, when it is determined that the value of j is smaller than 3, the pixel processing unit 103 determines whether or not the values of y [j] and ymini are equal (step S503). If it is determined that they are not equal, the process proceeds to step S508 described later. On the other hand, if it is determined that they are equal, the pixel processing unit 103 determines whether x [lv] is greater than x [j] (step S504). If it is determined that x [lv] is equal to or less than x [j], the process proceeds to step S506 described below. On the other hand, when it is determined that x [lv] is larger than x [j], the pixel processing unit 103 substitutes j for lv (step S505).

  Next, the pixel processing unit 103 determines whether x [j] is greater than or equal to x [rv] (step S506). If it is determined that x [j] is smaller than x [rv], the process proceeds to step S508 described later. On the other hand, when it is determined that x [j] is greater than or equal to x [rv], the pixel processing unit 103 substitutes j for rv (step S507). Next, the pixel processing unit 103 determines whether y [j] is smaller than ymini (step S508). If it is determined that y [j] is equal to or greater than ymini, the process proceeds to step S510 described below. On the other hand, when it is determined that y [j] is smaller than ymini, the pixel processing unit 103 substitutes y [j] for ymini and substitutes j for lv and rv (step S509).

  Next, the pixel processing unit 103 determines whether y [j] is larger than ymax (step S510). When it is determined that y [j] is equal to or less than ymax, the process proceeds to step S512 described later. On the other hand, when it is determined that y [j] is larger than ymax, the pixel processing unit 103 substitutes y [j] for ymax (step S511). Next, the pixel processing unit 103 divides j by adding 1 and divides it by 3, and substitutes the remainder for n, and y [n] −y which is an increment dy of y on the screen coordinates corresponding to the vertex j [j] is calculated (step S512).

  Next, the pixel processing unit 103 determines whether dy is not 0 (step S513). If it is determined that dy is 0, the pixel processing unit 103 substitutes 0 for an increment dx [j] of x on the screen coordinates corresponding to the vertex j (step S515). On the other hand, when it is determined that dy is not 0, the pixel processing unit 103 substitutes the value of (x [n] −x [j]) / dy for dx [j] (step S514). Next, the pixel processing unit 103 sets a value obtained by adding 1 to j as a new j (step S516). And the process after step S502 is repeated. Thereby, polygon parameters lv and rv are calculated.

  As described above, after the polygon parameters lv and rv are calculated, the following polygons (1) and (2) are determined to be back polygons. If the following expression (3) is satisfied, the front polygons and back polygons are determined. The intermediate state and the pixel processing unit 103 are determined. Note that “%” in Equation (2) is a remainder symbol. That is, the right side of Expression (2) is dx which is a remainder when (3 + rv−1) is divided by 3. Further, the state between the front polygon and the back polygon means a state in which the surface of the polygon 600 and the xz plane are parallel to each other as shown in FIG.

x [lv] = x [rv] (1)

dx [lv]> dx [(3 + rv−1)% 3] (2)

ymini = ymax (3)

  In the case of an opaque object, the depth value and brightness value of the screen coordinates to be described later are calculated for polygons satisfying Expression (1) and Expression (2) and polygons satisfying Expression (3), that is, polygons other than the front polygon. Therefore, the efficiency of image generation is improved.

  Here, calculation of the depth value and the luminance value of the screen coordinates will be described. The pixel processing unit 103 obtains the inclinations dz / dx and dz / dy in the screen coordinates of the polygon based on the vertex coordinates of the target polygon, and the internal depth value surrounded by the polygon vertices based on the inclination and the vertex coordinates. Is calculated. Further, the pixel processing unit 103 calculates an internal luminance value surrounded by the vertices of the polygon based on the luminance values of the vertices of the polygon. Then, the pixel processing unit 103 reads the depth value corresponding to the calculated screen coordinates from the storage unit 104, compares the depth value with the calculated depth value, and when the calculated depth value is small, the calculated depth value and the luminance value are stored in the storage unit 104. To store. Note that the depth value and the luminance value can be calculated using conventional methods, and detailed description thereof is omitted. Further, the inclinations dz / dx and dz / dy of the polygon in the screen coordinates may be calculated in the process of calculating the polygon parameter described above.

  The image output unit 105 generates an image based on the luminance value read from the storage unit 104 and displays the image on a display unit (not shown). Note that image generation is also performed by a method similar to the conventional method. As described above, according to the image generating apparatus of the present invention, it is possible to determine the front and back of a polygon without calculating the normal vector of the polygon, so that the efficiency of image generation can be improved.

  The image generation apparatus according to the present invention can determine the front and back of a polygon without calculating the normal vector of the polygon, and thus is useful for an image generation apparatus that improves the image generation efficiency of semitransparent objects and opaque objects. It is.

It is a block diagram which shows the structure of the image generation apparatus which concerns on embodiment of this invention. (A) It is a figure for demonstrating the viewpoint coordinate in the image generation apparatus which concerns on embodiment of this invention. (B) It is a figure for demonstrating the perspective coordinate in the image generation apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the screen coordinate in the image generation apparatus which concerns on embodiment of this invention. It is a figure which shows the polygon converted into the screen coordinate in the image generation apparatus which concerns on embodiment of this invention. It is a flowchart for demonstrating calculation of the polygon parameter in the image generation apparatus which concerns on embodiment of this invention. It is a figure which shows the intermediate state of the front polygon and the back polygon in the image generation apparatus which concerns on embodiment of this invention. It is a figure for demonstrating a front polygon and a back polygon.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image generation apparatus 101 Scene data receiving part (reception means)
102 vertex processing unit (first conversion means)
103 pixel processing unit (clipping means, second conversion means, calculation detecting means, determining means, controlling means)
104 Storage section (storage means)
105 Image output unit 600, a to g Polygon 700 Object 701 View point 702, 705 Line of sight 703, 706 Normal vector 704, 707 Angle formed by line of sight and normal vector

Claims (1)

Receiving means for receiving object information including at least coordinate information in the three-dimensional coordinates of vertices of an object composed of a plurality of polygons, and environment information including at least coordinate information in the three-dimensional coordinates of the viewpoint and light source for the object;
The coordinate information of the vertex of the object and the coordinate information of the light source received by the receiving means are converted into viewpoint coordinates with the viewpoint position as the origin, and a luminance value of the vertex of the object at the viewpoint coordinates is calculated. , First conversion means for converting the coordinate information of the vertices of the object converted into the viewpoint coordinates into perspective coordinates;
Clipping means for performing clipping for determining a drawing range of the object converted into the perspective coordinates by the first conversion means;
A second conversion unit configured to divide the object clipped by the clipping unit into polygons having three vertices in an XYZ coordinate system and convert the divided polygons to screen coordinates having a corner of a predetermined drawing range as an origin; When,
If there is one vertex that minimizes the Y coordinate among the vertices of the polygon converted to the screen coordinates by the second conversion means, one vertex that minimizes the Y coordinate and each other vertex Determining means for determining whether the front polygon or the back polygon is based on an increase in the X coordinate with respect to an increase in the Y coordinate ;
For the polygon determined to be a front polygon by the determination means, an internal depth value surrounded by the vertexes of the polygon is calculated based on the coordinate information of the vertexes of the polygon in the screen coordinates, and calculated. a calculation detecting means that to calculate the luminance value of the internal surrounded by the vertices of the polygon by interpolating the intensity values of the vertices of the object,
And control means for storing the depth value and the luminance value of the table polygon calculated in the previous hexane detecting means in the storage means,
An image generation apparatus.

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