JPH0632045B2 - Object image synthesizer - Google Patents

Description

The present invention relates to an object image compositing apparatus for compositing images for displaying an object.

[Conventional technology]

As a method of synthesizing digital images for displaying an object, there is a method called ray tracing method. In this method, the path of the light ray from the light source to the viewpoint is traced in the opposite direction,
The intersection determination process between the light ray and the object is performed, and the brightness of each pixel forming the image is calculated based on the result. An example of this ray tracing method is described in Reference 1: IPSJ Transactions, No. 25.
Vol. 6, No. 6, Hiroshi Deguchi, Hitoshi Nishimura, Hiroshi Yoshimura, Toru Kawada, Isao Shirakawa, Koichi Omura, Paper "High-speed image generation method in computer graphics system LINKS-1".

In order to perform image generation by such a ray tracing method at high speed, the space in which the object is defined is divided into a plurality of areas, and each area is assigned to one computer, and each computer is assigned. A parallel processing method has been proposed in which a light beam that passes through an area is processed. For details of this method, see Reference 2: Computer Graphics, Volume 18, No. 3,
Mark Dippe and John Swensen, "Unadaptive Subdivision Algorithm and Parallel"
Architecture Forerealistic Image Synthesis (An Adaptive Subdivision Algorithm and
Parallel Architecture for Realistic Image Synthesi
s) ”.

In the above method, the space is first divided into a plurality of rectangular parallelepiped areas, and each area is assigned to one computer. Next, the data of the object included in the assigned rectangular parallelepiped region is stored in each computer. Then, each computer performs an intersection determination process between a ray passing through the assigned area and an object included in the area. By this intersection determination processing,
When the object and the light beam intersect, reflection and transmission processing is performed on the surface of the object. Information about rays that do not intersect the object in that area is transferred to the computer assigned to the adjacent area.

In this way, each ray is determined to intersect only with an object included in the area through which the ray passes. Therefore, compared with the case where each ray is processed for intersection determination with all objects, the total processing amount is much smaller.

In addition, such intersection determination processing is executed in parallel in each computer. By adding this parallel processing effect, it is possible to combine images at a very high speed.

[Problems to be solved by the invention]

In such a conventional image synthesizing method, each computer performs intersection determination processing between a ray passing through the assigned area and an object included in the area. The amount of processing required for this is much smaller than the case where the intersection determination processing is performed for all objects, but it is also a huge amount of processing. Therefore, by the simple process of determining the intersection of the area where the object exists and the ray, only the objects that may intersect with this ray are selected in advance, and the conventional intersection determination process is performed only with these objects. There is a method.
An example of this method is Document 3: Pixel (PIXEL),
No. 37, Akimoto Akira, "Rapid Tracing Acceleration Techniques-Previous Techniques and ARTS Techniques". In this method, a row of unit cubes through which light rays pass is generated as a three-dimensional digital straight line. By using this three-dimensional digital straight line, the intersection of the region where the object exists and the light ray is determined at high speed.

However, in such a conventional method, the area in which an object exists is represented by storing, for each unit cube, information (for example, the object number) indicating all the objects included in the unit cube. . Therefore, there is a problem that the amount of data required to represent the area where the object exists becomes enormous.

In order to solve such a problem, the present invention can represent a range in which an object exists with a very small amount of data, and can use this to perform high-speed intersection determination processing. The purpose is to provide.

[Means for solving problems]

An object image synthesizing apparatus of the present invention divides a space defined by an initial ray generation unit that generates information about a plurality of light rays passing through each pixel from a viewpoint, an object information setting unit that sets information about the object, and a space defined by the object. Of a plurality of regions generated by performing the intersection determination process of a ray passing through this region and an object included in the region in charge, thereby calculating the luminance of the pixel. The brightness calculation unit includes a calculation unit and an image storage unit that stores the brightness calculated by the brightness calculation unit as the image, and the brightness calculation unit includes a plane in three directions that is perpendicular to each coordinate axis and is equidistant. Among the plurality of unit cubes generated by dividing the definition space of the object by a group, the row of unit cubes through which the light ray passes is 3
A straight line generating means for generating a three-dimensional digital straight line, and one of a plurality of regions generated by dividing the object definition space on a part or all of the plurality of planes of the brightness calculation unit. Area information storage means for storing the range of this area as the area in charge, existence range determining means for determining a unit cube included in the range of existence of the object in the area in charge, and the above-mentioned based on the determination of the existence range determining means Presence information storage means for storing the presence information of the object indicating whether or not each unit cube included in the area in charge is included in the presence range in correspondence with each unit cube, and generated by the straight line generation means. Read out the presence information corresponding to the row of unit cubes from the presence information storage means, and determine the unit cubes included in the existence range of the object in the area in charge. And the light selecting means for selecting a light beam over to the intersection determining means for performing intersection determination processing with the selected beam and the object in the light beam selecting means is provided.

[Action]

A method of determining an intersection between an object and a light ray in the object image synthesizing apparatus of the present invention will be described.

A plurality of cubes generated by dividing the object definition space by a plane group in three directions, which is composed of a plurality of planes that are perpendicular to each coordinate axis and are equally spaced, are referred to as a unit cube. Further, the object definition space is divided by a part or all of the plurality of planes to generate a plurality of regions. The area thus generated is a rectangular parallelepiped formed of one or a plurality of unit cubes, and each boundary surface of the rectangular parallelepiped is perpendicular to each coordinate axis. One of the plurality of areas is assigned as the area in charge of one brightness calculation unit. The range of the assigned area is stored in the area information storage unit provided in the brightness calculation unit.

Further, the existence range determination means provided in each brightness calculation unit is
First, an existence range of an object included in the area in charge is determined in the area in charge, a unit cube included in the area is determined, and information indicating the unit cube is transmitted to the existence information storage means.

The presence information storage means stores, for each unit cube included in the assigned area, presence information indicating whether or not the unit cube is included in the existing range of the object. Therefore, the existence information storage means first stores, as the existence information corresponding to all the unit cubes, a value indicating that it is not included in the existence range. Then, the information on the unit cube determined to be included in the existing range by the existing range determining means is received, and the value indicating that the unit cube is included in the existing range is stored as the existing information corresponding to the unit cube.

If the unit cube is within the range of the object,
The unit cube may contain objects inside. Further, if the unit cube is not included in the existence range of the object, the unit cube does not include the object.

Further, the straight line generating means provided in each brightness calculation unit sequentially generates a row of unit cubes through which light rays pass within the area in charge of the brightness calculation unit as a three-dimensional digital straight line. Then, the light ray selection means reads out the presence information corresponding to these unit cubes from the presence information storage means.

If even one of the generated unit cubes is included in the existence range of the object, it is determined that this ray may intersect with the object in the area in charge, and this ray is subjected to the intersection determination processing. To choose as. Also, if all the generated unit cubes are not included in the existence range of the object,
Since there is no possibility that this ray intersects the object in the area in charge, the intersection determination processing of this ray is not performed, and the information of this ray is transferred to the adjacent brightness calculation unit.

Then, the intersection determination means performs an intersection determination process between the light ray selected by the light ray selection means and the object.

〔Example〕

1 (a) and 1 (b) are configuration diagrams showing an object image synthesizing apparatus as one embodiment of the present invention, and FIG. 1 (a) is
FIG. 1 (b) is a block diagram showing a detailed configuration of the brightness calculation unit 3 shown in FIG. 1 (a). As shown in FIG. 1A, the present embodiment is provided with an initial light ray generation unit 1 that generates information on a plurality of light rays passing through each pixel of an image to be combined from a preset viewpoint. . Further, an object information setting unit 2 for setting the information of the displayed object is provided.

Furthermore, one of a plurality of regions generated by dividing the defined space of the object is in charge, and a ray passing through this region and an object included in the in-charge region (referred to as region S) A plurality of brightness calculation units 3 for calculating the brightness of each pixel by performing the intersection determination process are provided.
An image storage unit 4 for storing the brightness calculated by the brightness calculation unit 3 as an image is provided. This image storage unit 4
Sets the brightness of all pixels to 0 before performing image composition.

Then, these initial light ray generation unit 1 and object information setting unit 2
And a connection line 5 for transmitting information between the plurality of brightness calculation units 3 and the image storage unit 4. This connection line 5
An information input unit 6 is provided for inputting information from a keyboard, for example.

As shown in FIG. 1 (b), the brightness calculation section 3 is provided with another brightness calculation section 3 in charge of areas adjacent in the six directions and mutual communication means 31 for mutual communication. Further, a communication means 32 for communicating via the connection line 5 is provided. Further, a connection line 101 for transmitting information in the brightness calculation section 3 is provided.

FIG. 2 is an explanatory diagram showing a method of calculating the brightness I of the pixel p (i, j), in which the light source L, the objects O and O ′, and the point E are arranged as shown in the figure. As shown in FIG. 2, in the ray tracing method, the path of the ray from the light source L through the pixel p (i, j) to the viewpoint E is traced in the reverse direction, and the pixel p (i, j
j) The brightness is calculated. Where pixel p (i, j)
Will be referred to as the brightness of the light ray R generated in the opposite direction from the viewpoint E through the pixel p (i, j). In FIG. 2 and the following description, R, R ′, _{RL and the} like represent light rays, Corresponds to the direction, the direction corresponds to the direction of the ray R, and so on. The brightness I of the light ray R means the pixel p (i,
It is the intensity I of the light that enters the viewpoint E through j). The brightness I of the ray R is calculated by the following equation. (* Indicates multiplication) ref: the reflection coefficient of the object O dif: diffusion coefficient of the object O I ':' intensities of light incident from the direction I _L: incident light intensity from the light source L: unit normal vector of the surface of the object O ': R direction positive Reflection direction vector These two incident light intensity I ', in order to determine the I _L,
Starting from the intersection CP of the ray R and the object O, the direction is Two light rays R ′ and _RL are generated. In addition, the coefficients of I ′ and I _L for obtaining the brightness I are represented by light rays R ′ and R _L.
The attenuation rates G ′ and G _L of That is, the ray R
Is attenuated by the collision of the object O with the ray R ′,
R _L is generated. These attenuation factors G ′, G _L
Is G: The attenuation rate of the light ray R (= 1). By using these attenuation factors G ′ and G _L , the brightness I of the light ray R, that is, the brightness I of the pixel p (i, j)
Is calculated as follows.

I = G ′ * I ′ + G _L * I _{L When} the new rays R ′ and _RL are thus generated, the information of the ray R becomes unnecessary.

Further, as shown in FIG. 2, when the ray R ′ intersects the object O ′, rays R ″ and _RL ′ are similarly generated.
These attenuation factors G ″ and G _L ′ are similarly calculated by the following equations.

ref ': reflection coefficient of the object O'dif': diffusion coefficient of the object O '': unit normal vector of the surface of the object O ' In this way, the attenuation rate G ', _GL is integrated with the attenuation rate G'.

However, the processing of the ray R _L is different from the processing of the rays R and R ′.
When the ray R _L intersects the object, the intersection CP becomes a shadow of the object and cannot receive the illumination light of the light source L. Therefore, the brightness I _L of the light ray R _L becomes zero. If the ray R _L does not intersect any object, the intensity I _L of the ray R _{L is} the intensity of the light source L. Thus, light rays R towards the object, the handle is a ray R _L where R 'and directed to the light source L are different, it is necessary to distinguish between the type of light. Therefore,
A type C for distinguishing the type of the light ray is set to the light ray R. This type C is 0 when the ray R is directed to the object,
A value of 1 is given when going to the light source.

As shown in FIG. 2, a ray of light directed to the object generates a ray of light directed to a new object each time it collides with the object. Therefore, in order to calculate the brightness I of one pixel p, a large number of light rays need to be processed. But,
Since the light ray is attenuated each time it collides with an object, the influence of the light ray on the luminance I becomes almost negligible as the number of collisions increases.

Therefore, in order to limit the number of collisions of the light ray R, the number of times T is set for the light ray R. This number T indicates the number of possible collisions of the light ray R. If a ray R having a number of times T strikes an object and a ray R'to the object is generated, the number T'of rays R'is set to (T-1). If the ray R of which the number T is 0 collides with the object, the ray R'to the object is not generated but only the ray R _L to the light source L is generated.

Although there is only one light source L in FIG. 2, when a plurality of light sources L _i (i = 1, 2, ...) Are present, light rays traveling to all the light sources L _i must be generated. .
By the way, in the case of the light ray R _L directed to the light source, a new light ray is not generated even if it intersects with the object as described above.
The number of times T as the information of the light source R _L has no meaning. Therefore, when a plurality of light sources L _i exists, light as the number of times T of R _L, the ray R _L sets the number i of the light source towards (on computer processing, light R, the number of times for R 'T
The number i of the light source L _i with respect to the ray R _L is set so as to correspond to the setting of By setting the number i of the light source L _i instead of the thus rays R _L to the number of times T, even when a plurality of light sources L _i exists, the number i of the light source L _i of each light beam R _L is directed You know, so you can do it right.

For simplicity, only reflection on the surface of the object is considered here. If the transmission of the object is also taken into consideration, a ray in the transmission direction may be generated at the intersection of the object and the ray R. However, the type of this light ray is a light ray traveling toward the object, and if it is processed in the same manner as the above-mentioned light ray R ', the transmission of the object can be correctly expressed.

FIG. 3 is an explanatory diagram showing information on the light ray R to be set when the light ray R is generated. As shown in FIG. 3, when the light ray R is generated, as the information of the light ray R, the starting point positional relationship (S _x , S _y , S _z ) of the half line indicating the light ray R and the direction (d _x ,
d _y , d _z ) are set. The position (i, j) of the pixel p (i, j) affected by the brightness of the ray R is also set as the information of the ray R. Further, the attenuation rate G of the light ray R, the number T of the light ray R, and the type C of the light ray R are also set as the information of the light ray R.

FIG. 4 is an explanatory diagram showing information set in the light ray R in order to generate a row of unit cubes through which the light ray R is transmitted as a three-dimensional digital straight line. Here, a plane group perpendicular to the x coordinate axis and arranged at unit length intervals, a plane group perpendicular to the y coordinate axis and unit length intervals, and a unit length interval perpendicular to the z coordinate axis are arranged. Each of a plurality of cubes generated by dividing the object definition space with a plane group is called a unit cube. As shown in Figure 4, of the unit cube generated sequentially as a three-dimensional digital rays, last generation position of a unit cube _{(T X, T Y, T} Z) is, as the information of the ray R Is set. That this position _{(T X, T Y, T} Z) indicates the current position of the ray R, rays R is gradually updated according to pass an object definition space. Further, the error information ER for sequentially generating the three-dimensional digital straight line is also set as the information of the light ray R.
A three-dimensional digital straight line can be generated at high speed by adding the error information ER and making a determination. The meaning and calculation method of the error information ER are described in detail in the above-mentioned Document 3.

FIG. 5 is an explanatory diagram for explaining the operation of the initial light beam generator 1. As shown in FIG. 5, the initial ray generator 1 generates a ray R as a half line starting from the viewpoint E and passing through each pixel p (i, j) forming the image P.

Therefore, the position coordinates ((E _x , E _y , E _z ) of the viewpoint E are input to the initial ray generation unit 1 by the information input unit 6. Also, as information defining the image P to be combined. ,
The parameters indicating the plane and range of the image P are the information input unit 6
Input from. The initial ray generator 1 generates information on the ray R based on these parameters. An example of a method of obtaining the half line indicating the ray R is described in Reference 4: T. Whitted, Communication of ACM,
Volume 23, No. 6, pp. 343-349, Paper "An Improved Illumination Model for Shaded Display (An Improved Illumi
nation Model for Shaded Display) ".

Next, the position coordinates (E _X , E _Y , E _Z ) of the viewpoint E, which is the starting point of this half line, are set as the starting position coordinates (S _X , S _Y , S _Z ) of the ray R, and from the viewpoint E Pixel p
The direction toward the light ray R is set as the direction (d _X , d _Y , d _Z ) of the light ray R. In addition, the position (i,
j) is set as the pixel position ((i, j)) of the ray R.

In the initial light ray generation unit 1, the attenuation rate G of the generated light ray R is set to 1, that is, a state in which the light ray R is not attenuated at all. Further, as the number of times T, a constant value preset in the initial light ray generation unit 1 is given from the information input unit 6. Furthermore, as the type C, a value of 0 indicating a light ray toward the object is given.

In addition, among the intersections of the ray R generated in this way and the object definition space, the position coordinates (t _X , t
_Y , t _Z ) is obtained. This position coordinate (t _X , t _Y ,
t _Z ) is converted into an integer, a unit cube including this intersection is obtained, and this is used as a position (T _X , T _Y , T) as information of the ray R.
_Z ). This position (T _X , T _Y , T _Z )
Indicates a unit cube at the position where the ray R first enters the object definition space. Then, with this unit cube as the first unit cube, a row of unit cubes through which the ray R passes in the object definition space is generated in each luminance calculation unit 3 as a three-dimensional digital straight line.

In the subsequent processing, when the light ray R passes through the area S and is incident on another area S ′, the information of the light ray R is transferred between the brightness calculation units 3. At that time, the current position (T _X , T _Y , T _Z ) of the three-dimensional digital straight line as the information of the ray R
Is updated to the position of the unit cube including the intersection of the new area S ′ and the ray R.

Further, in the initial ray generation unit 1, the initial value of the error information ER for sequentially generating the three-dimensional digital straight line is calculated and set as the error information ER of the ray R. The method of calculating this initial value is described in detail in Document 3 as described above.

The initial ray generator 1 has a ray R having such information.
Are generated corresponding to all the pixels p (i, j) of the image P and are transferred to the luminance calculation unit 3.

FIG. 6 is an explanatory diagram showing the information of the object set in the object information setting unit 2. For simplicity of explanation, the displayed object is limited to a sphere, but the same can be applied to the case of displaying an object such as a polyhedron or a free surface.

As shown in FIG. 6, object information is input from the information input unit 6 and set in the object information setting unit 2. Information of the object _{O i} is set, the object _{O i} object number for distinguishing the _{n i,} spherical center coordinates as the object _{(x i, y i, z} i)
A radius r _i , a diffusion coefficient dif _i indicating the material of the object, and a reflection coefficient ref _i . Furthermore, as the information indicating the circumscribed area of the object O _i, the minimum rectangular parallelepiped range including the object is set.

FIG. 7 is an explanatory diagram showing a circumscribing region of a sphere as the object O _i . As shown in FIG. 7, the circumscribed area of the object O _i is
Range in x direction (x _i− , x _{i +} ), range in y direction (y
_i- , y _{i +} ) and a rectangular parallelepiped composed of a plurality of unit cubes represented by a range (z _i- , z _{i +} ) in the z direction. These values are integer values and are calculated by the following formula.

_{x i- = floor (x i- -r} i) x i + = ceil (x i + r i) y i- = floor (y i -r i) y i + = ceil (y i + r i) z i- = floor _{(z i -r i) z i} + = ceix (z i + r i) floor (a): maximum integer value not greater than a ceil (a): the minimum integer value Figure 8 not less than a, the object information It is an explanatory view showing information of a light source set up in setting part 2. For the sake of simplicity, the description is limited to the point light source only, but the same can be applied to the case of handling various types of illumination light such as parallel rays and spot lights. Information of the light source as the illumination of the object is input from the information input unit 6 and set in the object information setting unit 2 as shown in FIG. The information on the light source to be set is the point light source L
position coordinates of the _i a _{(x i, y i, z} i), the light source luminance I _Li. The brightness I _Li is a real value from 0 to 1. The value of the brightness I _Li indicates the brightness of the light source, and the value of 1 is the brightest, and the value of 0 is the darkest light source.

The object information and the light source information set in this manner are transmitted from the object information setting unit 2 to the brightness calculation unit 3 via the connection line 5.

FIG. 9 is an explanatory diagram showing a method of connecting a plurality of brightness calculation units 3 in a three-dimensional array. As shown in FIG. 9, the brightness calculation section 3 is connected in a three-dimensional array through the mutual communication means 31 provided in the brightness calculation section 3. That is, each brightness calculation unit 3 is connected to the brightness calculation units 3 on both sides in the x, y, and z directions, and the brightness calculation units 3 are connected.
And can mutually communicate information. Where x,
The a, b, and c-th luminance calculation units 3 in the y and z directions are set to (a,
(b, c) When called as the brightness calculation unit 3, (a, b,
c) The brightness calculation unit 3 calculates (a-1, b, c), (a + 1,
b, c), (a, b-1, c), (a, b + 1, c),
(A, b, c-1), (a, b, c + 1) luminance calculation unit 3
Connected with.

Further, the brightness calculation units 3 are arranged in the x, y, and z directions in the figure by A, B, and C, respectively, and the total number D of the brightness calculation units 3 is D = A * B * C.

FIG. 10 is an explanatory diagram showing a method of dividing the space defining the object into the assigned areas S assigned to the respective brightness calculation units 3. As shown in FIG. 10, by some or all of the plurality of planes serving as the boundary surface of the unit cube,
The object definition space is divided into a plurality of rectangular parallelepiped regions. By performing such division, each region can be configured by a plurality of or one unit cube.

Further, in this case, the division is performed so that the number of regions in the x direction is A, the number of regions in the y direction is B, and the number of regions in the z direction is C. Then, the (a, b, c) luminance calculation unit 3 is assigned the a-th area in the x direction, the b-th area in the y-direction, and the c-th area in the z-direction. As a result, all the divided areas can be assigned to one brightness calculation section 3.

Further, by performing such allocation, the other brightness calculation units 3 connected via the mutual communication means 31 are in charge of the respective adjacent areas.

11 and 12 are explanatory diagrams showing the contents of the area information indicating the area S in charge of the brightness calculation section 3. As shown in FIG. 11, the area information storage means 33 provided in the brightness calculation section 3 stores area information indicating the area S in charge of the brightness calculation section 3. As the area information, the values of (a, b, c) indicating the number in the x, y, z directions and the range (x, y, z) of the area S in charge as shown in FIG. 12 (x _- ,
_{x +), (y -,} y +), (z -, z +) and are stored. Since each area is composed of a plurality of or one unit cube, the value indicating these ranges is an integer value.

Further, in the brightness calculating section 3 existing on the outer periphery of the three-dimensional array, the brightness calculating section 3 may not be connected by the mutual communication means 31. Therefore, as shown in FIG. 11, whether or not the brightness calculation section 3 is actually connected in each direction connected by the mutual communication means 31 is stored in the area information storage means 33 as the presence / absence information. .

These area information is input from the information input means 6,
It is transmitted to each brightness calculation unit 3.

FIG. 13 is an explanatory diagram showing a process of transferring the information of the light ray R from the initial light ray generating section 1 to the luminance calculating section 3. As shown in FIG. 13, the information of all the rays R generated by the initial ray generator 1 is supplied to all the brightness calculators 3 via the connecting line 5.
Are transferred to all at once. Then, the information of the light ray R transferred from the initial light ray generation unit 1 is input to the initial information determination unit 38 provided in each brightness calculation unit 3 via the communication unit 32. At the same time, the information of the area S in charge stored in the area information storage unit 33 is read by the initial information determination means 38.

Position of the ray R input in this way (T _x , T _y , T _z )
Is set at the position where the ray R first enters the object definition space. Therefore, if this position (T _x , T _y , T
_{If z 1} ) is included in the service area S, the ray R will pass through the service area S first.

Therefore, the initial information determining means 38, the position of the light beam _{R (T x, T y,} T z) in the range of coverage areas S (x _-,
x ₊ ), (y ₋ , y ₊ ), and (z ₋ , z ₊ ) are compared.

If all three conditional expressions x ₋ ≦ T _x <x ₊ y ₋ ≦ T _y <y ₊ z ₋ ≦ T _z <z ₊ are satisfied, the position (T _x ,
T _y , T _z ) is included in the area S in charge, and the light ray R first passes through the area S in charge. In this case, the information of the light ray R is transferred from the initial information determination means 38 to the light ray information storage means 34 and stored therein.

If any of these conditional expressions does not hold, the light ray R is first incident on the other area S'in charge. Therefore, the information of the light ray R is not stored in the brightness calculation unit 3.

Through the above processing, the information of the light ray R generated by the initial light ray generation unit 1 is stored in the light ray information storage unit 34 of the brightness calculation unit 3 which is in charge of the first incident area.

FIG. 14 is an explanatory diagram showing information that causes the object information storage unit 35 and the light source information storage unit 36 provided in the brightness calculation unit 3 to store the object information and the light source information from the object information setting unit 2. All the object information and the light source information stored in the object information setting unit 2 are simultaneously transferred to all the brightness calculation units 3 via the connection line 5. The light source information storage unit 36 provided in the brightness calculation unit 3 stores all the light source information transferred via the communication unit 32.

Further, the initial information determination means 38 provided in the brightness calculation section 3
First receives the object information transferred via the communication means 32. Next, the range of the area S in charge of the brightness calculation unit 3 is read from the area information storage unit 33. The scope of the coverage area _{S (x -, x +)} , (y -, y +), (z -, z +) range of the circumscribed area of the object information _{(x i-, x i +)} , (y i- , Y
_{i +} ) and (z _i− , z _{i +} ) are compared.

15 (a) and 15 (b) are areas S in charge of the brightness calculation unit 3.
FIG. 7 is an explanatory diagram showing a process of comparing the object information with the circumscribed region. As shown in FIGS. 15A and 15B, the area S in charge
And the circumscribed area have no common part, at least one of the following conditional expressions is satisfied.

x ₋ ≧ x _{i +} x ₊ ≦ x _i- y ₋ ≧ y _{i +} y ₊ ≦ y _i- z ₋ ≧ z _{i +} z ₊ ≦ z _i- Therefore, the initial information determination means 38 evaluates these conditional expressions. , It is required to determine whether the area S in charge and the circumscribed area have a common part. As a result, when there is a common part, it is determined that the object O _i is included in the area S in charge, and all the information of the object O _i is stored in the object information storage unit 35. If there is no common part, it is not stored.

Through the above processing, of the object information stored in the object information setting unit 2, only the object information included in the area S in charge is stored in the object information storage unit 35 provided in the brightness calculation unit 3.

16 (a) and 16 (b) are explanatory views showing a method of determining the existence range of an object in the existence range determination means 40 provided in the brightness calculation unit 3. As shown in FIG. 16 (a), first, the existence range determination means 40 includes the object information storage means 3
The object information stored in No. 5 and the range of the assigned area S stored in the area information storage unit 33 are read out. Then, the range (x ₋ , of the circumscribed region of the object O _i as the object information,
x ₊ ), (y ₋ , y ₊ ), (z ₋ , z ₊ ), and the range (x _i− , x _{i +} ), (y _i− , y _{i +} ), (z _i− , z) of the area S in charge.
_{i +} ), the existence range (x ′ _i− , x ′ _{i +} ) of each object in the assigned area S (y ′ _i− , y ′ _{i +} ),
(Z ′ _i− , z ′ _{i +} ) is determined as follows.

x _- ≧ x _i- if _{x 'i- = x - x -} <x i- if _{x' i- = x i- x +} ≦ x i + if _{x 'i + = x + x} +> if x _{i +} If x ′ _{i +} = x _{i +} y ₋ ≧ y _i-, then y ′ _i- = y ₋ y ₋ <y _i- if y ′ _i- = y _i- y ₊ ≦ y _{i +,} then y ′ _{i +} = y ₊ y _+> y _{i +} if _{y 'i + = y i +} z - ≧ z i- if _{z' i- = z - z -} <z i- if _{z 'i- = z i- z +} ≦ z i + If z ′ _{i +} = z ₊ z ₊ > z _{i +,} then z ′ _{i +} = z _{i + For} simplicity, here, for simplicity, the common part between the circumscribed region of the object O _i and the area S in charge is defined as the existence of the object O _i . Determined as the area. However, if the existence range of the object O _i can be represented by a smaller rectangular parallelepiped as shown in FIG. 16B, this may be determined as the existence range.

Then, the existence range determination means 40 determines the existence ranges (x ′ _i− , x ′ _{i +} ) and (y ′ _i− , y ′) of the object O _i thus determined.
Information indicating all the unit cubes included in _{i +} ), (z ' _i- , z'i ₊ ) is transmitted to the existence information storage means 41.

The presence information storage unit 41 stores the presence information of the unit cube corresponding to each unit cube in the area S in charge, and stores the value 0 for all the presence information initially. When the value 0 is stored as this existence information, it indicates that the corresponding unit cube is not included in the existence range of the object, and when the value 1 is stored, the corresponding unit cube is the object. It is included in the existence range of. Therefore, when the value 0 is stored as the existence information corresponding to each unit cube, the unit cube does not include an object. Further, when the value 1 is stored as the existence information corresponding to the unit cube, the unit cube may include an object.

Then, the existence information storage means 41 includes the existence range determination means 4
The presence information corresponding to the unit cube indicated by the information transmitted from 0 is changed to the value 1 and stored. By this process,
The value 1 is stored as the existence information corresponding to all the unit cubes included in the existence range of the object O _i determined by the existence range determination unit 40.

By performing such processing for all the objects O _i , it is possible to set the presence information stored corresponding to the unit cube included in the existence range of all the objects O _i to the value 1.

FIG. 17 is an explanatory diagram showing a method of processing the information of the light ray R in the brightness calculation section 3. As shown in FIG. 17, the information of the light ray R stored in the light ray information storage means 34 is first read out and stored in the light ray selection means 42. At the same time, the light ray selecting means 42 transmits the information of the light ray R to the straight line generating means 43 to store the information. Then, the information selecting means 42 positions the light ray R as the information of the read light ray R (T _X ,
The presence information of the unit cube indicated by T _Y , T _Z ) is read from the presence information storage unit 41. If, when the presence information is 1, the position _{(T X, T Y, T} Z) because unit cube represented by are included in the existence range of the object, the ray R is possible to intersect the object There is a nature. Therefore, the ray selection means 42 uses the information of this ray R as the intersection determination means 39.
To the intersection determination processing.

Further, when the existence range is 0, this unit cube is not included in the existence range of the object, and therefore there is no possibility that the ray R intersects with the object in this unit cube. Therefore, the light ray selection means 42 sends control information to the straight line generation means 43 to generate a unit cube through which the light ray R passes next.

18 (a) and 18 (b) are explanatory views showing a straight line generating method in the straight line generating means 43. As shown in FIG. FIG. 18 (a),
As shown in (b), first, the straight line generating means 43 receives the information of the light ray R from the light ray selecting means 42 and stores this information. Then, each time the control information from the light ray selection means 42 is received, one unit cube through which the light ray R passes is generated by the addition determination processing of the error information ER which is the information of the stored light ray R.

In order to generate such a unit cube, the straight line generation means 43 first performs addition determination processing of the error information ER, and updates the error information ER based on the result. Next, the straight line generation means 43 selects and determines the coordinate axis for generating the unit cube from among the x, y, and z coordinate axes based on the result of this addition determination processing, and determines the selection information SEL. The value of the selection information SEL is either 0, 1, or 2, and these values indicate the x, y, and z coordinate axes, respectively. At the same time, the straight line generating means 43 generates the unit cube direction DIR
Also decide. The value of this direction DIR is 1 or -1.
The method for determining these values is shown in Document 3 as described above.

For example, as shown in FIG. 18 (a), when the unit cube next to the unit cube ( _Tx , _Ty , _Tz ) is generated, the addition determination process of the error information ER of the ray R in the straight line generating means 43 is performed. When the selection information SEL is determined to be 0 and the direction DIR is determined to be 1, the straight line generating means 43 generates a unit cube (T _x +1, T _y , T _z ). Also, select information
When SEL is set to 0 and direction DIR is set to -1, the straight line generating means 43 generates a unit cube ( _Tx- 1, _Ty , _Tz ).

Then, the straight line generating means 43 uses the newly generated unit cube (T _x ′, T _y ′, T _z ′) at the position (E _x , T _y , T _z ) in the stored information of the light ray R. ).
By doing so, the position of the ray R (T _x , T _y , T _z )
Is updated so that this position (T _x , T _y , T _z ) indicates the last unit cube in the row of unit cubes as a three-dimensional digital line.

The straight line generation means 43 also determines the selected selection information SEL and the direction D.
The position of the new ray R (T _x , T _y , T
_z ) is within or outside the area S in charge. When it is determined that the light ray R is out of the range, the passing direction of the light ray R is determined, and the information of the light ray R and the passing direction are sent to the light ray information transfer means 44.

For example, as shown in FIG. 18B, when the generated unit cube is out of the range of the area S in charge, the direction in which the unit cube is generated becomes the passage direction of the light ray R.

In order to make such a determination, the straight line generation means 43 reads the value of the range of the area S in charge indicated by the selection information SEL and the direction DIR from the area information storage means 33. Then, by comparing this value with the value indicated by the selection information SEL of the positions ( _Tx , _Ty , _Tz ), it is determined whether the generated unit cube is within or outside the area S in charge. .

For example, the selection information SEL is 0 as shown in FIG.
If the direction DIR is 1, the value of x _{+ in} the range is read. This value x ₊ is compared with the value T _x indicated by the selection information SEL of the positions (T _x , T _y , T _z ) to make the following determination.

When T _x > x ₊ is out of range When T _x ≦ x ₊ is in range When the selection information SEL is 0 and the direction DIR is −1,
It reads the value of _- the range of x. This value x ₋ and the position (T _x ,
The value T _x indicated by the selection information SEL of T _y and T _z ) is compared to make the following determination.

When T _x <x ₋ is out of range When T _x ≧ x ₋ is in range Thus, the straight line generating means 43 is at the position (T _x , T _y ,
If it is determined that T _z is within the range, the updated ray R
The position (T _x , T _y , T _z ) is sent to the ray selection means 42. Upon receiving this, the ray selecting means 42 changes the new position (T
_The presence information corresponding to the unit cube indicated by _x , T _y , T _z ) is read from the presence information storage means 41, and the selection process of the light ray R is continued.

Further, if it is determined that the value is out of the range, the straight line generating means 4
3 sends control information indicating that it is out of range to the light ray selecting means 42. In this case, the light ray R does not pass through the unit cube included in the existence range of the object in the area S in charge. Therefore, it is not necessary to perform the intersection determination processing between the ray R and the object. Therefore, the straight line generation means 43 transfers the information of the light ray R, the selection information SEL and the direction DIR to the light ray information transfer means 44.
Send to. Ray information transfer means 44 which has received these information
Performs the process of transferring the information of the light ray R to the adjacent brightness calculation unit 3.

Through the above processing, the light ray selection means 42 selects only the light ray R that may intersect with the object in the area S in charge,
The information can be sent to the intersection determination means 39. Then, the intersection determination unit 39 reads the information of the object included in the area S in charge from the object information storage unit 35, and performs the intersection determination process with the light ray R.

As a result of this intersection determination processing, if the ray R intersects the object, a new ray R'or ray RL is generated from the ray R, and information on these rays R'and RL is stored in the ray information storage. It is stored in the means 34. However, when the number of times T as information of the ray R is 0, a new ray R'is not generated as described above. Such intersection determination processing is shown in the above-mentioned documents and FIG.

Further, as a result of the intersection determination processing in the intersection determination means 39,
The information on the ray R that does not intersect the object must be transferred to the adjacent brightness calculation unit 3. Therefore, the intersection determination means 3
9 sends control information to the straight line generating means 43. The straight line generating means 43 stores the information of the light ray R already sent from the light ray selecting means 42. Therefore, the straight line generating means 43
When receiving the control information from the intersection determination unit 39, the unit continuously generates unit cubes until the generated position ( _Tx , _Ty , _Tz ) falls outside the range of the area S in charge. Then, the information of the light ray R and the selection information SEL and the direction DIR when the generated position (T _x , T _y , T _z ) is out of the range of the assigned area S are transferred to the light ray information transfer means 44. In this way, the straight line generation means 43 transfers information to the light ray information transfer means 44 almost in the same manner as when the control information is received from the light ray selection means 42.

Next, the transfer processing of the information of the light ray R in the light ray information transfer means 44 will be described. This ray information transfer means 44
Performs the transfer processing of the information of the light ray R also sent from the straight line generating means 43 based on the selection information SEL and the direction DIR sent from the straight line generating means 43. In order to perform this transfer processing, the light beam information transfer means 44 first selects the selection information SE.
Information on whether or not the brightness calculation unit 3 is connected in the direction indicated by L and the direction DIR is stored in the area information storage unit 33.
Read from.

If the brightness calculation unit 3 is connected in this direction, the information of the light ray R is transmitted to the brightness calculation unit 3 connected in the direction indicated by the selection information SEL and the direction DIR via the mutual communication means 31. To transfer.

For example, the selection information SEL output from the straight line generation means 43
Is 0 and the direction DIR is 1, the information of the ray R is transferred to the brightness calculation unit 3 connected in the x ₊ direction. Similarly, when the selected selection information SEL output from the straight line generating means 43 is 0 and the direction DIR is −1, the information of the light ray R is transferred to the brightness calculation unit 3 connected in the x ₋ direction. The information of the light ray R thus transferred is read from the mutual communication means 31 in the adjacent brightness calculation section 3 and stored in the light ray information storage means 34.

Further, the selection information SEL sent from the straight line generation means 43
When the brightness calculation unit 3 is not connected in the direction indicated by and the direction DIR, the ray R goes out of the object definition space. Therefore, it can be seen that this ray R does not intersect the object in all object definition spaces.

Therefore, the light ray information transfer means 44 outputs the information of this light ray R to the brightness determination means 37. The brightness determining means 37 checks the type C of the light ray R as the information of the light ray R, and when the light ray R is a light ray heading for the light ray L, reads the information of the light source from the light ray information storage means 36, The brightness I of the ray R is determined. However, when there are a plurality of light sources L _i , the light source number i indicated by the number T of the light sources R is referred to, the information of the light source L _i of that number is read, and the brightness I
To decide. This determination process is based on the above-mentioned documents and the second document.
As shown in the figure. Then, via the communication means 32, the pixel p (i,
The bright luminance I is added to j).

Also, if this ray is a ray going to the object,
Since the brightness I of the light ray R becomes 0, the information of the light ray R is erased without performing the addition processing of the brightness I.

By the intersection determination processing described above, the synthesis of the image P is completed at the time when all the information of the light ray R stored in the light ray information storage unit 34 of each brightness calculation unit 3 is processed.

〔The invention's effect〕

In the object image synthesizing apparatus of the present invention, when synthesizing images by the ray tracing method by parallel processing for dividing a space,
Since it is only necessary to perform the intersection determination processing only on the rays that pass through the existence range of the object within the area in charge of each brightness calculation unit, it is possible to sufficiently obtain the effect of speeding up by the parallel processing.

Moreover, corresponding to each unit cube included in the area in charge,
Since whether or not the unit cube is included in the existence range of the object is stored, it is possible to determine whether or not each light ray passes through the existence range of the object at high speed by using the three-dimensional digital straight line.

Moreover, since the amount of information to be stored corresponding to each unit cube is very small, the required amount of data can be greatly reduced compared to the conventional case.

[Brief description of drawings]

1 (a) and 1 (b) are an overall configuration block diagram showing an entire object image synthesizing apparatus according to an embodiment of the present invention and a configuration block diagram showing a detailed configuration of a brightness calculation unit, and FIG. 2 is a pixel p. Explanatory drawing which shows the calculation method of the brightness | luminance I of (i, j), 3rd
The figure shows the information of the ray R to be set when the ray R is generated, and FIG. 4 is the information set in the ray R in order to generate a row of unit cubes through which the ray R passes as a three-dimensional digital straight line. FIG. 5, FIG. 5 is an explanatory diagram for explaining the operation of the initial light ray generation unit 1, FIG. 6 is a diagram showing information of an object set in the object information setting unit 2, and FIG. FIG. 8 is an explanatory view showing a circumscribing area of a sphere, FIG. 8 is a view showing information on a light source set in the object information setting unit 2, and FIG. 9 is a method of connecting a plurality of brightness calculation units 3 in a three-dimensional array. Explanatory drawing, first
FIG. 0 is a diagram showing a method of dividing a space defining an object into assigned areas S assigned to each brightness calculation section 3, and FIGS. 11 and 12 are area information diagrams showing the assigned area S of the brightness calculation section 3, respectively. FIG. 13 is a block diagram showing a process of transferring the information of the light ray R from the initial light ray generation unit 1 to the brightness calculation unit 3, and FIG. 14 is object information provided in the brightness calculation unit 3. Storage means 35 and light source information storage means 36
15 is a block diagram showing a process of storing the object information and the light source information from the object information setting unit 2, FIG. 15A and FIG. 15B are comparisons of the area S in charge of the brightness calculation unit 3 and the circumscribed area of the object information. FIG. 16 is an explanatory view showing the processing, in which the area S in charge and the circumscribing area respectively have a common part and a case where it does not have a common part. FIG. 17 is a block diagram showing a method of processing the information of the light ray R in the brightness calculating section 3, and FIG. 18 is a straight line generating means 4
It is explanatory drawing which shows the generation method of the straight line in 3. 1 ... Initial ray generation unit, 2 ... Object information setting unit, 3 ...
Luminance calculation unit, 4 ... Image storage unit, 5 ... Connection line, 6 ...
Information input section, 31 ... Mutual communication means, 32 ... Communication means, 33 ... Area information storage means, 34 ... Ray information storage means, 35 ... Object information storage means, 36 ... Light source information storage means, 37 ...... Luminance deciding means, 38 ...... Initial information deciding means, 39 ...... Crossing deciding means, 40 ...... Existence range deciding means, 41 ...... Existence information storing means, 42 ...... Light ray selecting means, 43 ...... Straight line generating means , 44 ... Ray information transfer means.

Claims (1)

[Claims] 1. A ray tracing method for tracing the path of a ray from a ray to a viewpoint in the opposite direction to perform intersection determination processing between an object and a ray, and calculating the brightness of each pixel forming an image for displaying the object. In the object image synthesizing device based on, an initial light ray generation unit that generates information of a plurality of light rays that pass through each pixel from the viewpoint, an object information setting unit that sets information of the object, and calculate the brightness of the pixel. An object image synthesizing device comprising a plurality of brightness calculation units and an image storage unit that stores the brightness calculated by the brightness calculation unit as an image, wherein each of the brightness calculation units defines a definition space of the object. Straight line generation means for generating, as a three-dimensional digital straight line, a row of unit cubes through which a ray passes among a plurality of unit cubes generated by dividing plane groups that are perpendicular to each coordinate axis and are equally spaced, A range of a region in charge of the brightness calculation unit, which is one region among a plurality of regions generated by dividing the definition space of the object on some or all of the plurality of planes of the group Area information storage means for storing, an existence range determining means for determining an existence range in which a common part of the circumscribing area of the object and the responsible area is realized in the unit cube unit, and based on the determination of the existence range determining means Occurrence information storage means for storing the presence information of the object indicating whether or not the unit cubes included in the assigned area are included in the presence range, and the straight line generation means. Light for reading out the existence information corresponding to the column of the unit cube from the existence information storage means and selecting a light ray passing through the unit cube included in the existence range of the object in the area in charge. Cross-judgment between a light ray passing through the area in charge and the object included in the area in charge, comprising line selection means and cross-judgment means for performing intersection judgment processing between the light ray selected by the light ray selection means and the object. An object image synthesizing apparatus, characterized in that the brightness of the pixel is calculated by performing processing.