JP2007156773A - Image generation device, image generation method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image generation technology for generating the image of the head part of a character arranged in a virtual space by a drawing method widely used for comics or animation. <P>SOLUTION: The generation part 504 of an image generation device 501 generates an image where the face of a character arranged in a virtual space is viewed from the point of view arranged in the virtual space, and when a first direction fixed to the head part of the character deviates from a second direction from the head part of the character to the point of view, a correction part 503 corrects the position of the object arranged in the head part of the character so as to be close to the point of view, and the generation part 504 generates the image. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides an image generation apparatus, an image generation method, and a computer that are suitable for generating an image of a character's head placed in a virtual space using a drawing method widely used in manga and animation. Related to the program.

  Conventionally, when representing characters such as humans and animals in computer graphics (CG), the skeleton is abstracted with a line segment object called a bone, and the position of the bone around each bone is fixed. There has been proposed a technique for obtaining the shape of the skin by obtaining the skin shape by abstracting the shape of the skin according to the position of the points. That is, the bone determines the general posture and shape of the character, and the skin corresponds to the surface shape and appearance shape of the character.

Such a technique is disclosed in the following document.
Tim Coleman, Sherri Sheridan, Digital Studio Translation, Aiming Pro-Animator Maya Character Animation, pages 255-277, Bone Digital, Inc., published April 25, 2002

  [Non-Patent Document 1] discloses a technique for changing the facial expression of a character by changing the shape of an object such as an eye, nose, or mouth arranged on the head of the character.

  On the other hand, character drawing in Japanese manga and animations has unique characteristics. That is, the position of the mouth and nose when the character is viewed from an oblique side is deviated from the position of the mouth and nose obtained when the character is photographed in a three-dimensional configuration. It is.

  For example, when the character's hair is standing or when the character has horns, it is also possible to draw the hair and horns so that they do not overlap so that the head of the character is conspicuous It is one of the simple drawing.

  This is because, when a person or animal is represented as a painting, the character's head is made more attractive by attracting the viewer's eyes by using a drawing method different from that of photographs and attracting the viewer's eyes. It is a painting technique for showing, and it is also a traditional technique applied in Ukiyo-e, for example.

  Therefore, when a character modeled as an object placed in a virtual space is displayed on the screen using CG technology, it is not only based on perspective projection such as taking a picture, but as described above, such as manga and animation. There is a great demand to be able to cope with the unique drawing methods used in Japan.

  The present invention solves the above-described problems, and is an image generation apparatus and image suitable for generating an image of the head of a character placed in a virtual space by a drawing method widely used in manga and animation. It is an object of the present invention to provide a generation method and a program for realizing these on a computer.

  In order to achieve the above object, the following invention is disclosed in accordance with the principle of the present invention.

  An image generation apparatus according to a first aspect of the present invention includes a generation unit and a correction unit, and is configured as follows.

  Here, the generation unit generates an image of the head of the character (including the “face” of the character) placed in the virtual space as viewed from the viewpoint placed in the virtual space.

  The head of a character is generally formed by an object representing a planar shape, a curved surface shape, or a three-dimensional shape, such as a combination of bones, control points, and skins, or a polyhedron composed of various polygons. Objects such as the nose, mouth, eyes, ears, and hair are arranged on the surface of the character's head object.

  The image generation unit generates an image showing the state of the virtual space viewed from the viewpoint by various three-dimensional CG techniques such as perspective projection and parallel projection.

  On the other hand, when the first direction fixed to the character's head and the second direction from the character's head to the viewpoint are shifted from each other, the correction unit is arranged on the character's head. The position of the object is corrected so as to approach the viewpoint, and the generation unit generates the image.

  The correction unit corrects the positions of objects such as the nose, mouth, eyes, ears, and hair prior to image generation by the generation unit.

  The first direction fixed to the character's head is typically the front direction when the character faces the front, and when the second direction from the character's head to the viewpoint matches the first direction, This is the case where it is directly opposite the character's head. Therefore, in such a case, objects such as the nose and the mouth remain arranged at the reference position.

  On the other hand, when the second direction is shifted from the first direction, for example, when the second direction is set to the left from the first direction starting from the character, the left half of the character's head is displayed in the image more. Will be.

  In such a case, in the expression of manga and animation, a drawing method in which the mouth and nose are moved to the left starting from the character may be used.

  In the present invention, an effect similar to that of such a drawing method is obtained by correcting the position of the object so as to approach the viewpoint.

  According to the present invention, an image of a character's head placed in a virtual space can be easily generated by a drawing method widely used in manga and animation.

  In the image generating apparatus of the present invention, the correction unit is configured to correct the position of the object by rotating the position of the object around a rotation axis fixed to the head of the character. Can do.

  The rotation axis for rotating the nose and mouth objects typically employs a straight line connecting the center of the character's spine or neck and the top of the head. When the nose or mouth object is rotated about the straight line as the rotation axis, the nose or mouth object moves to the left or right on the surface of the character's head.

  According to the present invention, when an image of the head of a character placed in a virtual space is generated, the position after movement of the object can be easily obtained.

  In the image generation device of the present invention, the correction unit rotates around the rotation axis from a plane extending from the rotation axis and the first direction to a plane extending from the rotation axis and the second direction. The angle can be acquired, and the position of the object can be corrected by rotating the position of the object by the rotation amount obtained by multiplying the acquired rotation angle by a proportional constant greater than 0 and less than 1. .

  In the present invention, how much the viewpoint is shifted to the left and right from the front of the character is checked, and the object such as the nose and the mouth is moved by rotating the object by an amount of rotation that interpolates the left and right shift.

  In order to obtain such a rotation amount, a component in the rotation axis direction of the outer product of the direction vector in the first direction and the direction vector in the second direction is obtained, and the vector of the component in the rotation axis direction is multiplied by the proportional constant. May be adopted as the rotation vector of the object.

  According to the present invention, when an image of the head of a character placed in a virtual space is generated, the position after movement of the object can be easily obtained.

  In the image generation device of the present invention, the correction unit is configured to correct the position of the object by an amount that is associated in advance with the amount of deviation between the first direction and the second direction. be able to.

  That is, assuming a spherical surface centered on the character's head, the spherical surface is divided into sections, and the correction amount of the object position is determined for each section. Then, the section of the spherical surface where the half line from the character's head to the viewpoint intersects is examined, and the position of the object is corrected by the correction amount associated with the section.

  According to the present invention, when an image of the head of a character placed in a virtual space is generated, the position after movement of the object can be easily obtained.

  In the image generation device of the present invention, the correction unit is configured to correct the position of the object when the deviation between the first direction and the second direction is equal to or less than a predetermined threshold. Can do.

  The present invention provides a restriction on the direction of the viewpoint that corrects the position of the object. For example, when the viewpoint is on the back of the character, it is meaningless to move the eyes and mouth arranged on the face. On the other hand, for objects that can be seen from the back, such as hair and corners, object movement processing can be performed.

  According to the present invention, when an image of the head of a character placed in a virtual space is generated, an object whose position is to be corrected can be appropriately selected to suppress calculation processing.

  In the image generation apparatus of the present invention, the object can be configured to be an object representing the nose or mouth of the character.

  The present invention relates to a preferred embodiment of the above invention. In the expression of manga and animation, when drawing the appearance of a character seen from diagonally left or diagonally right, the positions of the nose and mouth are greatly different from the case of taking a photograph of a three-dimensional model. Therefore, in the present invention, the positions of these are corrected.

  According to the present invention, it is possible to easily generate an image of a character's head placed in a virtual space by moving the position of the nose and mouth in accordance with a drawing method widely used in manga and animation. it can.

  An image generation method according to another aspect of the present invention is executed by an image generation apparatus including a generation unit and a correction unit, and is configured as follows.

  That is, in the generation step, the generation unit displays an image of the head of the character arranged in the virtual space as viewed from the viewpoint arranged in the virtual space.

  On the other hand, in the correction process, prior to the generation process, the correction unit is displaced from the first direction fixed to the character's head and the second direction from the character's head to the viewpoint. The position of the object placed on the head of the character is corrected so as to approach the viewpoint, and the image is generated in the generation step.

  A program according to another aspect of the present invention is configured to cause a computer to function as the above-described image generation device and to cause the computer to execute the above-described image generation method.

  The program of the present invention can be recorded on a computer-readable information storage medium such as a compact disk, flexible disk, hard disk, magneto-optical disk, digital video disk, magnetic tape, and semiconductor memory.

  The above program can be distributed and sold via a computer communication network independently of the computer on which the program is executed. The information storage medium can be distributed and sold independently from the computer.

  ADVANTAGE OF THE INVENTION According to this invention, the image generation apparatus suitable for producing | generating the image of the head of the character arrange | positioned in the virtual space by the drawing method widely used by manga and animation, and an image generation method, and these are made into a computer. Can be provided.

  Embodiments of the present invention will be described below. In the following, for ease of understanding, an embodiment in which the present invention is realized using a game information processing device will be described. However, the embodiment described below is for explanation, and the present invention is described. It does not limit the range. Therefore, those skilled in the art can employ embodiments in which each or all of these elements are replaced with equivalent ones, and these embodiments are also included in the scope of the present invention.

  FIG. 1 is a schematic diagram showing a schematic configuration of a typical information processing apparatus that performs the function of the image generation apparatus of the present invention by executing a program. Hereinafter, a description will be given with reference to FIG.

  The information processing apparatus 100 includes a CPU (Central Processing Unit) 101, a ROM 102, a RAM (Random Access Memory) 103, an interface 104, a controller 105, an external memory 106, an image processing unit 107, and a DVD-ROM. (Digital Versatile Disc ROM) drive 108, NIC (Network Interface Card) 109, and audio processing unit 110.

  A DVD-ROM storing a game program and data is loaded into the DVD-ROM drive 108 and the information processing apparatus 100 is turned on to execute the program, thereby realizing the image generation apparatus of the present embodiment. Is done.

  The CPU 101 controls the overall operation of the information processing apparatus 100 and is connected to each component to exchange control signals and data. Further, the CPU 101 uses arithmetic operations such as addition / subtraction / multiplication / division, logical sum, logical product, etc. using an ALU (Arithmetic Logic Unit) (not shown) for a storage area called a register (not shown) that can be accessed at high speed. , Logic operations such as logical negation, bit operations such as bit sum, bit product, bit inversion, bit shift, and bit rotation can be performed. In addition, the CPU 101 itself is configured so that saturation operations such as addition / subtraction / multiplication / division for multimedia processing, vector operations such as trigonometric functions, etc. can be performed at a high speed, and those provided with a coprocessor. There is.

  The ROM 102 records an IPL (Initial Program Loader) that is executed immediately after the power is turned on, and when this is executed, the program recorded on the DVD-ROM is read out to the RAM 103 and execution by the CPU 101 is started. The The ROM 102 stores an operating system program and various data necessary for operation control of the entire information processing apparatus 100.

  The RAM 103 is for temporarily storing data and programs, and holds programs and data read from the DVD-ROM and other data necessary for game progress and chat communication. Further, the CPU 101 provides a variable area in the RAM 103 and performs an operation by directly operating the ALU on the value stored in the variable, or temporarily stores the value stored in the RAM 103 in the register. Perform operations such as performing operations on registers and writing back the operation results to memory.

  The controller 105 connected via the interface 104 receives an operation input performed when the user executes the game.

  The external memory 106 detachably connected via the interface 104 stores data indicating game play status (past results, etc.), data indicating game progress, and log of chat communication in the case of a network match ( Data) is stored in a rewritable manner. The user can record these data in the external memory 106 as appropriate by inputting an instruction via the controller 105.

  A DVD-ROM mounted on the DVD-ROM drive 108 stores a program for realizing the game and image data and audio data associated with the game. Under the control of the CPU 101, the DVD-ROM drive 108 performs a reading process on the DVD-ROM loaded therein, reads out necessary programs and data, and these are temporarily stored in the RAM 103 or the like.

  The image processing unit 107 processes the data read from the DVD-ROM by an image arithmetic processor (not shown) included in the CPU 101 or the image processing unit 107, and then processes the processed data on a frame memory ( (Not shown). The image information recorded in the frame memory is converted into a video signal at a predetermined synchronization timing and output to a monitor (not shown) connected to the image processing unit 107. Thereby, various image displays are possible.

  The image calculation processor can execute a two-dimensional image overlay calculation, a transmission calculation such as α blending, and various saturation calculations at high speed.

  Also, polygon information arranged in the virtual three-dimensional space and added with various texture information is rendered by the Z buffer method, and the polygon arranged in the virtual three-dimensional space from the predetermined viewpoint position is determined in the direction of the predetermined line of sight It is also possible to perform high-speed execution of operations to obtain a rendered image overlooking the top.

  Further, the CPU 101 and the image arithmetic processor operate in a coordinated manner, so that a character string can be drawn as a two-dimensional image in a frame memory or drawn on the surface of each polygon according to font information that defines the character shape. is there.

  The NIC 109 is used to connect the information processing apparatus 100 to a computer communication network (not shown) such as the Internet, and is based on the 10BASE-T / 100BASE-T standard used when configuring a LAN (Local Area Network). To connect to the Internet using an analog modem, ISDN (Integrated Services Digital Network) modem, ADSL (Asymmetric Digital Subscriber Line) modem, cable television line A cable modem or the like and an interface (not shown) that mediates between these and the CPU 101 are configured.

  The audio processing unit 110 converts audio data read from the DVD-ROM into an analog audio signal and outputs the analog audio signal from a speaker (not shown) connected thereto. Further, under the control of the CPU 101, sound effects and music data to be generated during the progress of the game are generated, and sound corresponding to this is output from the speaker.

  When the audio data recorded on the DVD-ROM is MIDI data, the audio processing unit 110 refers to the sound source data included in the audio data and converts the MIDI data into PCM data. If the compressed audio data is in ADPCM format or Ogg Vorbis format, it is expanded and converted to PCM data. The PCM data can be output by performing D / A (Digital / Analog) conversion at a timing corresponding to the sampling frequency and outputting it to a speaker.

  Furthermore, a microphone 111 can be connected to the information processing apparatus 100 via the interface 104. In this case, the analog signal from the microphone 111 is subjected to A / D conversion at an appropriate sampling frequency so that processing such as mixing in the sound processing unit 110 can be performed as a PCM format digital signal.

  In addition, the information processing apparatus 100 uses a large-capacity external storage device such as a hard disk so as to perform the same function as the ROM 102, the RAM 103, the external memory 106, the DVD-ROM mounted on the DVD-ROM drive 108, and the like. You may comprise.

  The information processing apparatus 100 described above corresponds to a so-called “consumer video game apparatus”, but the present invention can be realized as long as it performs image processing to display a virtual space. Therefore, the present invention can be realized on various computers such as a mobile phone, a portable game device, a karaoke apparatus, and a general business computer.

  For example, a general computer, like the information processing apparatus 100, includes an image processing unit that includes a CPU, RAM, ROM, DVD-ROM drive, and NIC and has simpler functions than the information processing apparatus 100. In addition to having a hard disk as an external storage device, a flexible disk, a magneto-optical disk, a magnetic tape, and the like can be used. Further, not the controller 105 but a keyboard or a mouse is used as an input device.

  FIG. 2 is an explanatory diagram showing a model of a character's face in the virtual space. Hereinafter, a description will be given with reference to FIG.

  The model of the character's face 201 includes a bone 202 from the neck 252 to the top 251 and control points 203 of objects arranged on the surface of the face such as the eyes 253, the nose 254, the mouth 255 (represented by black circles in the figure). And).

  A plurality of control points 203 are assigned to each of the eyes 253, the nose 254, and the mouth 255. These control points 203 define the skin shape and the shape of a line drawing drawn on the surface of the character's face 201.

  The posture of the bone 202 in the virtual space is associated one-to-one with a direction 204 (hereinafter referred to as “first direction”) that indicates which direction the character's face 201 is facing. In order to facilitate understanding, hereinafter, the front direction of the character starting from the center point 205 of the character's face 201 is adopted as the first direction 204. The first direction 204 can be specified by the direction vector d in the first direction.

  A skin shape representing the three-dimensional shape of the character's face 201 is obtained from the coordinates of the control point 203 of the object.

  The skin shape obtained in this way is generally an aggregate of polygons (or curved surfaces), and the appearance of these seen from the viewpoint 206 arranged in the virtual space is three-dimensionally obtained by perspective projection or parallel projection. An image is generated by graphics technology and displayed on a display device such as a display.

  Hereinafter, in order to indicate the direction of the viewpoint 206 with respect to the character's face 201, the direction from the center point 205 to the viewpoint 206 of the character's face 201 is referred to as a second direction 207. The second direction 207 can be specified by the direction vector s in the second direction.

  The direction vector d and the direction vector s are unit vectors, and | d | = | s | = 1.

  In order to facilitate understanding, the position vector of the control point 203 with respect to the center point 205 of the character's face 201 is assumed to be r. In this figure, the position vector r is illustrated for the control point 203 at the left end of the lips.

  In the following description, among the objects arranged on the character's face 201, the description will be given with particular attention to the mouth 255. However, the same technique is applied to various objects such as the eyes 253, the nose 254, and the shape of the hair (not shown). Such embodiments can be applied and are also within the scope of the present invention.

  Conventionally, the basic position of the object control point 203 relative to the bone 202 is fixed. That is, even if the bone 202 changes its position and posture in the virtual space while the facial expression of the character remains constant, the basic position of the control point 203 is changed in conjunction with this, and the shape of the character's face is changed. There was no change in the skin shape itself.

  Also, changing the relative position of the object to the control point 203 with respect to the bone 202 from its basic position changes the shape of the character's face, nose, mouth, etc. as shown in [Non-Patent Document 1]. It was only when changing the facial expression of the character.

  Therefore, when the image of the character's face 201 with a certain expression arranged in the virtual space is viewed from the viewpoint 206, the relative position of the control point 203 of the object to the bone does not change. The skin shape of the character's face was also constant.

  3, 4, and 5 are explanatory diagrams illustrating a state in which a face 201 of a character having various expressions is viewed from a viewpoint 206 arranged in front of the character 201 in the related art. FIG. 3 shows a normal expression, FIG. 4 shows a laughing expression, and FIG. 5 shows a screaming expression.

  In these examples, the first direction 204 and the second direction 207 coincide. That is, d = s.

  As described above, in order to change the expression of the character's face 201, the position of the control point 203 relative to the bone 202 is changed. However, in the conventional technique, once the expression is determined, the position of the viewpoint 206 is changed. Even so, the relative position of the control point 203 with respect to the bone 202 remains fixed.

  6, 7, and 8 are explanatory diagrams illustrating a state in which the character's face 201 is viewed from the viewpoint 206 arranged on the right side when viewed from the character in the related art. Each corresponds to a situation in which the character's face 201 corresponding to the facial expressions of FIGS. 3, 4, and 5 is viewed from different viewpoints 206.

  In these examples, the first direction 204 and the second direction 207 do not match and there is a shift. That is, d ≠ s. Considering the cross product d × s of vectors, the direction of the cross product d × s is downward (the direction from the top 251 to the neck 252 of the character's face 201), and the angle formed by the two vectors d and s (the front of the viewpoint 206) This is equivalent to a deviation from the direction.) Where θ is θ = arcsin (| d × s |).

  Now, looking at the facial expression of the character's face 201 shown in FIGS. 6, 7, and 8, for viewers familiar with Japanese manga and animation, the mouth position is shifted to the left from the center of the character's face. I get the impression that This is particularly noticeable in the example shown in FIG.

  This is the reason why viewers receive such an impression, but in general drawing methods of Japanese manga and animation, taking into account the placement balance as a two-dimensional picture, the mouth and nose depending on the orientation of the character's face This is because it is a traditional technique to fine-tune the position.

  In the present invention, when the first direction 204 and the second direction 207 are deviated as described above, the positions of the mouth and nose are finely adjusted in accordance with the general drawing method of Japanese manga and animation.

  For ease of understanding, the resulting images will be described before describing embodiments of the present invention in detail. 9, 10, and 11 are explanatory diagrams showing how the face 201 of the character with various expressions is viewed from the viewpoint 206 arranged in front of it in the technique of the present invention. FIG. 9 shows a normal expression, FIG. 10 shows a laughing expression, and FIG. 11 shows a screaming expression.

  FIG. 12 is an explanatory diagram in which the images of the character's face 201 shown in FIGS. 8 and 11 are displayed in an overlapping manner.

  As can be seen by comparing FIGS. 9 to 11 and FIGS. 6 to 8, in the image generated by the technique of the present invention, the character's nose and mouth have moved slightly to the left. This can also be seen from the fact that in the figure shown in FIG. 12, the outline and eyes of the face are not blurred, while the nose and mouth are blurred and displayed twice.

  In the present technology, the positions of the mouth and nose are moved in this way because the viewpoint 206 is shifted to the right side when viewed from the character face 201. If the viewpoint 206 is shifted to the left as viewed from the character's face 201, the character's mouth moves slightly to the right in images based on the drawing method in Japanese manga and animation. That is, the character's mouth is moving so as to approach the viewpoint 206.

  Based on the principle of the present invention, in the embodiment described below, when the first direction 204 and the second direction 207 are shifted, the control point 203 of the mouth 255 of the character face 201 is changed to the bone 202 of the character face 201. Is moved around the axis of rotation so as to approach the viewpoint 206 slightly. Details will be described below.

  FIG. 13 is an explanatory diagram showing a schematic configuration of the image generation apparatus according to the embodiment of the present invention. Hereinafter, a description will be given with reference to FIG.

  The image generation apparatus 501 is typically realized by operating software on the information processing apparatus 100 described above, and includes a storage unit 502, a correction unit 503, and a generation unit 504.

The storage unit 502 stores various types of information on the model of the character's face 201 described above. Specifically, the following information is stored.
Information on the position and posture of the bone 202 in the virtual space. The information may be managed based on the global coordinate system in the virtual space, or the information may be managed in a form depending on the bone 211 of the neck of the character to which the bone 202 is connected and the bone such as the spine. It is good to be done. These pieces of information characterize the coordinate information of the center point 205 of the character's face 201 (typically fixed to the bone 202 constituting the central axis of the character's face 201) and the posture of the bone. Information on the direction vector d in the first direction 204 or information that can uniquely derive these information by calculation is also included.
The mouth 255 in the coordinate system fixed to the bone 202 (as described above, the same can be applied to the eyes 253, the nose 254, etc., but for the sake of easy understanding, in the following description, only the mouth 255 is used. The reference position information of the control point 203 will be described as an example. As described above, the reference position of the control point 203 is different for each facial expression of the character. When the viewpoint 206 is in front of the character's face 201, an image is generated using the reference position information itself.
Information on the position of the viewpoint 206. It is common to manage information based on the global coordinate system in the virtual space. For example, when it is desired to display on the screen what a character sees from a pet or mascot that the character is taking, it is fixed to the bone 202. The position in the coordinate system, the position in the coordinate system fixed to the bone 211 such as the neck bone 211 or the spine of the character to which the bone 202 of the character to which the bone 202 is connected may be adopted.

  When the image generation device 501 is used to realize a game device, these pieces of information are updated as appropriate by an instruction input from the user via the controller 105 or a calculation process of the CPU 101 that simulates a physical law.

In addition, an area for temporarily storing the following information is secured in the storage unit 502 between the start of processing and the generation of an image.
Information on position coordinates for image generation of the control point 203 of the mouth 255. This is because, as described later, various techniques can be considered as a method for correcting the position of the control point 203. Therefore, which coordinate system is to be stored as a reference is appropriately selected according to the correction method. It is possible.

  Therefore, an external storage device such as the RAM 103, the external memory 106, and the hard disk functions as the storage unit 502 under the control of the CPU 101.

  FIG. 14 is a flowchart showing the flow of control of image generation processing executed by the image generation apparatus 501. Hereinafter, a description will be given with reference to FIG.

  When the process is started, the correcting unit 503 first calculates a direction vector s in the second direction 207 in a predetermined coordinate system (step S601). Specifically, based on the information stored in the storage unit 502, the position coordinate of the viewpoint 206 in the coordinate system is obtained, and from this, the vector obtained by subtracting the position coordinate of the center point 205 in the coordinate system is By multiplying the reciprocal of the length of the vector, a unit vector having the same direction and direction can be obtained. The unit vector thus obtained is the direction vector s.

  When obtaining position coordinates in a predetermined coordinate system from information stored in the storage unit 502, a known coordinate transformation technique can be applied.

  Next, the direction vector d in the first direction 204 is acquired (step S602). From the posture of the bone 202, the direction vector d can be calculated uniquely.

  The direction vector d is compared with the direction vector s, and it is determined whether or not there is a deviation between them (step S603). If there is no deviation (step S603; No), the information of each reference position of the control point 203 is copied to the information storage area of the position coordinates for image generation in the storage unit 502 (step S604).

  In step S603, the process may proceed to step S603 even when the difference between the direction vector d and the direction vector s is larger than a predetermined threshold. For example, when the character is viewed from the viewpoint 206 behind, the mouth 255 does not appear in the image, so that it is not necessary to make corrections.

  Then, the generation unit 504 generates a three-dimensional graphics image based on the position coordinate information of the control points stored in the information storage area of the position coordinates for image generation in the storage unit 502 and other various information. (Step S605), and this process is terminated.

  For the generation of 3D graphics images, various techniques for obtaining the character's skin shape as disclosed in [Non-Patent Document 1] and forming the appearance of the character with polygons and curved surfaces, as seen from the viewpoint 206, are shown. Techniques such as perspective projection for generating an image and parallel projection (this corresponds to “perspective transformation in which the viewpoint 206 is moved to the infinity point along the direction vector s”) can be employed.

  Therefore, the CPU 101 functions as the generation unit 504 in cooperation with the RAM 103 and the image processing unit 107.

  On the other hand, when there is a difference between the direction vector d and the direction vector s (step S603; Yes), the correction unit 503 corrects the position coordinates of the control point 203 of the mouth 255 so as to approach the viewpoint 206 (step S606). The correction result is copied and written in the information storage area of the position coordinates for image generation in the storage unit 502 (step S607), and the process proceeds to step S604. In the example shown in FIG. 2, there are four control points 203 to be corrected for position coordinates (and three control points 203 for the nose 254).

  Therefore, the CPU 101 functions as the correction unit 503 in cooperation with the RAM 103 and the like.

  Various techniques for correcting the position coordinates of one control point 203 will be described below. When the position vector representing the reference position of the control point 203 in the predetermined coordinate system is r and the position vector of the corrected position 213 of the control point 203 is r ′, the correction is performed as follows. In FIG. 2, the control point 203 at the left end of the mouth 255 is shown as the position of the control point 203 to be processed.

The first method is a method in which the control point 203 is brought very close to the control point. When f (d, s) is a function for calculating the scalar quantity of the deviation between the direction vector d and the direction vector s, the correction is performed as follows.
r '= r + f (d, s) s

  FIG. 15 is an explanatory diagram of the character face 201 as viewed from above the head, showing how the position vector r of the control point 203 is brought close to the viewpoint and corrected to r ′ by this method. Hereinafter, a description will be given with reference to FIG.

  Since the direction vector s is a unit vector from the center point 205 of the character face 201 toward the viewpoint 206, the position vector r ′ of the corrected position 213 of the control point 203 is the position vector of the original position of the control point 203. Compared to r, it is closer to the viewpoint 206 by the length f (d, s).

  In the example shown in this figure, since the viewpoint 206 exists on the right side when viewed from the center point 205 of the character's face 201, the corrected position 213 of the control point 203 is also on the right side where the viewpoint 206 exists when viewed from the center point 205. Will be moved to.

  In this figure, the control point 203 at the left end of the character's mouth 255 is corrected, and the size of f (d, s) s is drawn large for easy understanding. A sufficient effect can be obtained with a very small size.

  In the above display example, the control point 203 of the nose 254 is also moved. However, in the example shown in this figure (and the figures shown below), the left end of the control point of the mouth 255 is easy to understand. Only the control point 203 is corrected.

Various modes can be considered for f (d, s), but it is desirable that the function increase as the deviation between the direction vector d and the direction vector s increases. For example, if k is a positive constant,
f (d, s) = k | ds |;
f (d, s) = k | ds | ² ;
f (d, s) = k | d × s |;
f (d, s) = k | d × s | ² ;
f (d, s) = k arcsin (| d × s |)
f (d, s) = k arccos (| d ・ s |)
A method that employs a function such as Further, a stepped function may be further applied to the right side of each function. In this way, the correction amount is associated with the deviation between d and s.

  The second method is a method of considering an axis vector c (| c | = 1), which is a unit vector fixed to the character's face 201, and rotating the position vector r around the axis vector c. An axis vector c is also shown in FIG.

  FIG. 16 is an explanatory diagram of the character face 201 as viewed from above the head, showing how the position vector r of the control point 203 is brought close to the viewpoint and corrected to r ′ by this method. Hereinafter, a description will be given with reference to FIG.

  The axis vector c typically coincides with the direction of the bone 202 and is the direction from the neck 252 toward the crown 251. In this case, even if the viewpoint 206 is shifted to the left and right from the front of the character and further shifted to the upper and lower sides, the mouth 255 is only corrected to the left and right, not to the upper and lower sides.

  There are various known coordinate transformation techniques for rotating the given position coordinates around the rotation axis by the given angle to obtain the position coordinates after rotation, and any of them can be adopted. It is. A typical example will be described below.

First, it is obtained how much angle the viewpoint 206 is rotated by rotation around the axis vector c. This rotation angle is defined as θ. Since the outer product d × s of the direction vector d and the direction vector s represents the rotation from the direction vector d to the direction vector s, the component in the c direction of d × s corresponds to the rotation around the axis vector c. That is,
(d × s) · c = | d × s | cosθ;
θ = arccos (| d × s | / ((d × s) ・ c))
Thus, θ can be obtained.

  Next, the position vector r is rotated by an angle ψ = g (d, s) around the axis vector c to obtain a corrected position vector r ′. Therefore, the position vector r and the position vector r ′ are arranged on a circumference 214 (indicated by a dotted line in this drawing) of a circle having the center point 205 as the center.

When using the above θ, using constant h (0 <h <1),
ψ = g (d, s) = hθ = h arccos (| d × s | / ((d × s) ・ c))
And

  In the example shown in this figure, since the viewpoint 206 exists on the right side when viewed from the center point 205 of the character's face 201, the corrected position 213 of the control point 203 is also on the right side where the viewpoint 206 exists when viewed from the center point 205. Will be moved to.

In general, g (d, s) is a function that increases as the difference between d and s increases, and any function is adopted as long as 0 ≦ g (d, s) ≦ θ is satisfied. be able to. Therefore, by properly selecting the value of the constant k,
g (d, s) = f (d, s);
g (d, s) = hf (d, s)
Or the like. In this way, the correction amount is associated with the deviation between d and s.

To obtain the result r 'obtained by rotating the position vector r around the axis vector c = (c _x , c _y , c _z ) by the angle ψ, it is possible to use a quaternion or a rotation matrix. is there. Hereinafter, a method using a quaternion will be described. However, when a coordinate system fixed to the bone 202 is used, the rotation calculation can be easily performed by matching the axis vector c with any coordinate axis.

Now, the quaternion Q representing this rotation is
Q = (c _x sin (ψ / 2), _cy sin (ψ / 2), c _z sin (ψ / 2), cos (ψ / 2))
It can be expressed as

The quaternion R for the position vector c = (r _x , r _y , r _z ) is
R = (r _x , r _y , r _z , 0)
It can be expressed as

Then, the operation for rotating the quaternion R by the quaternion Q is as follows when the quaternion for the position vector r ′ is R ′:
R '= QRQ ^*
Can be expressed as Where ^* is the quaternion conjugate.
R '= (r _x ', r _y ', r _z ', r _w ')
If,
r '= (r _x ', r _y ', r _z ')
It is.

  In addition, it is also possible to adopt a method of obtaining the vector r ′ by rotating the vector r around the vector d × s by the angle ψ. In this case, depending on the position of the viewpoint 206, the corrected position of the mouth 255 also moves up and down.

  In addition, the correction amount and the correction direction are prepared in a table format in advance in association with the combination of the positional relationship between the vector d and s and the vector c at that time. It is also possible to obtain r ′ from r by referring to the data.

  17, 18, and 19, after correcting the positions of the mouth 255 and the nose 254 by shifting the viewpoint 206 of the face 201 of the character with various facial expressions to the right side when viewed from the character in the technique of the present invention. It is explanatory drawing which shows a mode that this was seen from the front of the character. Each corresponds to the examples of FIGS.

  As can be seen from these figures, the positions of the mouth 255 and the nose 254 are shifted to the left side of the image by correcting the positions of the control points 203 that define the shapes of the mouth 255 and the nose 254 closer to the viewpoint 206. It is supposed to be.

  In particular, in the correction of the position of the mouth 255, all of the control points 203 are moved to the left side. However, in the correction of the position of the nose 254, a part of the control points 203 (the control point at the lower end of the nose 254) is moved to the left side. ing. In this way, it is possible to limit the control point 203 for correcting the position to a part.

  Such movement correction of the position of the object due to the change in the position of the viewpoint 206 does not actually occur, but by performing the correction, the position of the object in the image viewed from the viewpoint 206 is changed to manga or animation. It is very similar to the drawing method in.

  Therefore, according to the present invention, when an image of a character's face is generated by a character's three-dimensional model and three-dimensional graphics, a viewer who is familiar with the drawing method of manga and animation is in line with the drawing method. It will be possible to provide “natural face” images.

  As described above, according to the present invention, an image generating apparatus, an image generating method, and the like that are suitable for generating an image of a head of a character arranged in a virtual space by a drawing method widely used in manga and animation, In addition, it is possible to provide a program that realizes these on a computer.

It is a schematic diagram which shows the outline | summary structure of the typical information processing apparatus which performs the function of the image generation apparatus of this invention by running a program. It is explanatory drawing showing the model of the face of the character in virtual space. In prior art, it is explanatory drawing which shows a mode that the face of the character was seen from the viewpoint arrange | positioned in front of the character. In prior art, it is explanatory drawing which shows a mode that the face of the character was seen from the viewpoint arrange | positioned in front of the character. In prior art, it is explanatory drawing which shows a mode that the face of the character was seen from the viewpoint arrange | positioned in front of the character. In prior art, it is explanatory drawing which shows a mode that the face of the character was seen from the viewpoint arrange | positioned on the right side seeing from the character. In prior art, it is explanatory drawing which shows a mode that the face of the character was seen from the viewpoint arrange | positioned on the right side seeing from the character. In prior art, it is explanatory drawing which shows a mode that the face of the character was seen from the viewpoint arrange | positioned on the right side seeing from the character. In this embodiment, it is explanatory drawing which shows a mode that the face of the character was seen from the viewpoint arrange | positioned on the right side seeing from the character. In this embodiment, it is explanatory drawing which shows a mode that the face of the character was seen from the viewpoint arrange | positioned on the right side seeing from the character. In this embodiment, it is explanatory drawing which shows a mode that the face of the character was seen from the viewpoint arrange | positioned on the right side seeing from the character. It is explanatory drawing which superimposes and displays the image of the face of the character of a prior art, and the image of the character's face of this embodiment. It is explanatory drawing which shows schematic structure of the image generation apparatus which concerns on this embodiment. It is explanatory drawing which shows the flow of control of the calculation process performed with an image generation apparatus. It is explanatory drawing which looked at the mode that the position vector r of a control point was brought close to a viewpoint, and was corrected to r 'from the upper part of the character's head. It is explanatory drawing which looked at the mode that the position vector r of a control point was brought close to a viewpoint, and was corrected to r 'from the upper part of the character's head. In this embodiment, it is explanatory drawing which shows a mode that the state after correcting the position of a mouth and a nose as a character's face is seen from the viewpoint arrange | positioned on the right side seeing from a character is seen from the front of the character. is there. In this embodiment, it is explanatory drawing which shows a mode that the state after correcting the position of a mouth and a nose as a character's face is seen from the viewpoint arrange | positioned on the right side seeing from a character is seen from the front of the character. is there. In this embodiment, it is explanatory drawing which shows a mode that the state after correcting the position of a mouth and a nose as a character's face is seen from the viewpoint arrange | positioned on the right side seeing from a character is seen from the front of the character. is there.

Explanation of symbols

100 Information processing apparatus 101 CPU
102 ROM
103 RAM
104 Interface 105 Controller 106 External Memory 107 Image Processing Unit 108 DVD-ROM Drive 109 NIC
DESCRIPTION OF SYMBOLS 110 Speech processing part 111 Microphone 201 Character face 202 Face bone 203 Control point 204 1st direction (front direction of a character)
205 Center point 206 Viewpoint 207 Second direction (direction from character to line of sight)
211 Bone of neck 213 Position after correction of control point 214 Circumference around the center point 251 Head 252 Neck 253 Eye 254 Nose 255 Mouth 501 Image generation device 502 Storage unit 503 Correction unit 504 Generation unit

Claims (8)

A generating unit that generates an image of the head of the character placed in the virtual space as seen from the viewpoint placed in the virtual space;
When the first direction fixed to the character's head and the second direction from the character's head to the viewpoint are shifted, the position of the object placed on the character's head is An image generation apparatus comprising: a correction unit that corrects the image to approach the viewpoint and causes the generation unit to generate the image. The image generation apparatus according to claim 1,
The image generation apparatus characterized in that the correction unit corrects the position of the object by rotating the position of the object around a rotation axis fixed to the head of the character. The image generation apparatus according to claim 2,
The correction unit acquires a rotation angle around the rotation axis from a plane extending from the rotation axis and the first direction to a plane extending from the rotation axis and the second direction. An image generating apparatus, wherein the position of the object is corrected by rotating the position of the object by a rotation amount obtained by multiplying the rotation angle by a proportional constant greater than 0 and less than 1. The image generation apparatus according to claim 1, wherein
The correction unit corrects the position of the object by an amount associated in advance with an amount of deviation between the first direction and the second direction. The image generation apparatus according to any one of claims 1 to 4, wherein:
The correction unit corrects the position of the object when the difference between the first direction and the second direction is equal to or less than a predetermined threshold. The image generation apparatus according to any one of claims 1 to 5,
The image generation apparatus, wherein the object is an object representing the nose or mouth of the character. An image generation method executed by an image generation device including a generation unit and a correction unit,
A generating step in which the generating unit displays an image of the head of the character placed in the virtual space as seen from the viewpoint placed in the virtual space;
An object placed on the head of the character when the correction unit is displaced from the first direction fixed to the head of the character and the second direction from the head of the character to the viewpoint; An image generation method comprising: a correction step of correcting the position of the image so as to approach the viewpoint and generating the image in the generation step. Computer
A generating unit that generates an image of the head of the character placed in the virtual space as seen from the viewpoint placed in the virtual space;
When the first direction fixed to the character's head and the second direction from the character's head to the viewpoint are shifted, the position of the object placed on the character's head is A program that is corrected so as to approach a viewpoint and functions as a correction unit that causes the generation unit to generate the image.

Images