JPWO2007074728A1 - Uneven texture generation program and uneven texture generation apparatus - Google Patents

Abstract

An uneven texture that realistically represents the characteristics of a biological skin is generated. The virtual particle arrangement unit 102 sets a closed space CS in the virtual three-dimensional space, and arranges a plurality of virtual particles P in the closed space. The virtual particle growing unit 112 grows the virtual particles P according to the growth pattern of the skin cells of the organism. The external force calculation unit 111 calculates van der Waals force f, gravity FG, and constraint force FS that act on each virtual particle P. The position calculation unit 113 calculates the position of each virtual particle by solving the equation of motion of each virtual particle P. The uneven texture generating unit 104 projects the grown virtual particles P on the bottom surface BS to generate an uneven texture. [Selection] Figure 2

Description

  The present invention relates to a computer graphics technique.

  In recent years, wrinkles composed of fine irregularities have been widely adopted as patterns on the housing surface of home appliances and the surface of automobile instrument panels. There are various types of wrinkles, but among them, many are used that are based on the surface shape of animal skin such as reptiles. On the other hand, when a designer of home appliances or the like forms a wrinkle on a housing or the like of a home appliance, it is common to select a favorite one from a predetermined wrinkle pattern and apply it to the surface of the design target article. Has been made. For this reason, when there is no wrinkle suitable for the design object, a new wrinkle needs to be generated.

  On the other hand, in Non-Patent Document 1, for the purpose of automatically generating a detailed shape of an object surface that affects the quality of a CG image, the object surface is subjected to pseudo Voronoi division using a particle model, and each divided polygon is divided into polygons. On the other hand, a technique for generating a detailed shape of an object surface by generating a subdivision curved surface with fractal noise is disclosed.

However, when creating a new wrinkle, it is common for designers to make some arrangements to existing wrinkles, or to arrange an actual animal skin pattern, etc. There was a certain limit to the generation of the grain that realistically represented the skin of animals. In addition, the technique of Non-Patent Document 1 does not take into account the growth pattern of biological skin cells, and leaves room for further improvement in order to more realistically represent the characteristics of biological skin.
Kazuaki Miyata, Takayuki Ito, Kenji Shimada, “Generation of organic Textures with Controlled Anisotropy and Directionality via packing rectangular and EllipticalCells, IEEE CG & A Vol. .23 No.3. Pp.38-45,2003) ", Information Processing Society of Japan, 62nd National Convention Special Track (2) Proceedings, Special 2-53-60

  The objective of this invention is providing the uneven | corrugated texture production | generation program and the uneven | corrugated texture production | generation apparatus which represent the characteristic of the skin of a living organism realistically.

  The uneven texture generation program according to the present invention is an uneven texture generation program for generating an uneven texture, which sets a closed space in a virtual three-dimensional space and has a predetermined mass and a predetermined size in the set closed space. Virtual particle placement means for placing a plurality of virtual particles, and simulating the growth pattern of biological skin cells, increasing the number of virtual particles placed by the virtual particle placement means and the size of each virtual particle; Virtual particle growth means for growing each virtual particle in the closed space; interparticle force calculation means for calculating an interparticle force acting between the virtual particles determined based on the distance between the virtual particles; Position calculation means for calculating the position of each virtual particle by solving the equation of motion of each virtual particle when interparticle force is applied to each virtual particle; Based on the location and size, it is intended for causing a computer to function as uneven texture generating means for generating an uneven texture.

  The uneven texture generating device according to the present invention is an uneven texture generating device that generates an uneven texture, wherein a closed space is set in a virtual three-dimensional space, and a predetermined mass and a predetermined size are set in the set closed space. Virtual particle placement means for placing a plurality of virtual particles having the same, and the growth pattern of biological skin cells are simulated to increase the number of virtual particles placed by the virtual particle placement means and the size of each virtual particle Virtual particle growth means for growing each virtual particle in the closed space; and interparticle force calculation means for calculating an interparticle force acting between the virtual particles determined based on a distance between the virtual particles; Position calculation means for calculating the position of each virtual particle by solving the equation of motion of each virtual particle when the interparticle force is applied to each virtual particle, and the position and position of the virtual particle in the closed space Based on size and is characterized in that it comprises a concave-convex texture generating means for generating an uneven texture.

  According to these configurations, the number and size of the virtual particles in the closed space are increased according to the growth pattern of the skin cells of the organism. An interparticle force determined based on the distance between the virtual particles is acting on each virtual particle existing in the virtual three-dimensional space, and the interparticle force acting on each virtual particle is calculated.

  Further, the position of each virtual particle is calculated by solving the equation of motion of each virtual particle when an interparticle force is applied to each virtual particle as an external force. And the uneven | corrugated texture is produced | generated based on the position and magnitude | size of the virtual particle in closed space.

  That is, when the closed space is assumed to be skin tissue, the size and number of virtual particles are determined according to the growth pattern of the skin cells contained in the skin tissue, and the uneven texture is determined based on the position and size of the virtual particles. Since it is generated, it is possible to generate an uneven texture that more realistically represents animal skin characteristics.

It is a block diagram which shows the hardware constitutions of the uneven | corrugated texture production | generation apparatus by embodiment of this invention. It is a functional block diagram of the uneven | corrugated texture production | generation apparatus shown in FIG. It is a flowchart which shows operation | movement of this uneven | corrugated texture production | generation apparatus. It is the figure which showed the closed space produced | generated in virtual three-dimensional space. (A), (b) is the figure which showed an example of the pattern texture. It is a graph which shows the van der Waals force of Formula (1), the vertical axis | shaft shows f (w) and the horizontal axis has shown w. It is the figure which showed the Van der Waals force which acts on a virtual particle. It is a figure explaining the constraint force which acts on virtual particles. It is a graph of the function shown in Formula (4), the vertical axis | shaft has shown the increase number of the virtual particle added newly, and the horizontal axis has shown the growth time. It is the figure which showed the closed space at the time of the end of simulation. It is a figure explaining the process which produces | generates an uneven | corrugated texture. It is a figure which shows an example of the uneven | corrugated texture produced | generated by this uneven | corrugated texture production | generation apparatus, (a), (c), (d) shows the produced | generated uneven | corrugated texture, without producing | generating a potential field in closed space. , (B) shows the uneven texture generated when the potential field PF is generated in the closed space CS. It is the figure which showed the rendering result when the uneven | corrugated texture produced | generated using this uneven | corrugated texture production | generation apparatus is bump-mapped on the dashboard of a motor vehicle, and the virtual three-dimensional model of the interior of a motor vehicle was rendered.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a hardware configuration of an uneven texture generating device according to an embodiment of the present invention. The concavo-convex texture generating apparatus is composed of a normal computer or the like, and includes an input device 1, a ROM (read only memory) 2, a CPU (central processing unit) 3, a RAM (random access memory) 4, an external storage device 5, and a display device. 6 and a recording medium driving device 7. Each block is connected to an internal bus, and various data and the like are input / output through this bus, and various processes are executed under the control of the CPU 3.

  The input device 1 includes a keyboard, a mouse, and the like, and is used by an operator to input various data and operation commands. The ROM 2 stores a system program such as BIOS (Basic Input / Output System). The external storage device 5 is composed of a hard disk drive or the like, and stores a predetermined OS (Operating System), an uneven texture generation program, and the like. The CPU 3 reads an uneven texture generation program or the like from the external storage device 5 and controls the operation of each block. The RAM 4 is used as a work area for the CPU 3.

  The display device 6 is composed of a liquid crystal display device or the like, and displays various images under the control of the CPU 3. The recording medium driving device 7 includes a CD-ROM drive, a flexible disk drive, and the like.

  The uneven texture generation program is stored in a computer-readable recording medium 8 such as a CD-ROM and distributed on the market. The user installs the uneven texture generation program in the computer by causing the recording medium driving device 7 to read the recording medium 8. Alternatively, the uneven texture generation program may be installed in a computer by storing the uneven texture generation program in a server on the Internet and downloading from the server.

  FIG. 2 shows a functional block diagram of the uneven texture generating apparatus shown in FIG. The uneven texture generating apparatus includes a processing unit 100, a storage unit 200, an input unit 300, and a display unit 400. The processing unit 100 includes functions of a potential field generation unit 101, a virtual particle arrangement unit 102, a simulation execution unit 103, an uneven texture generation unit 104, a rendering unit 105, and a display control unit 106. These functions are realized by the CPU 3 executing the uneven texture generation program.

  The potential field generation unit 101 reads a pattern texture selected by the user by operating the input unit 300 from the pattern texture storage unit 201, and generates a potential field in a closed space according to the read pattern texture. Here, the potential field is a virtual object that gives repulsive force to the virtual particles arranged in the virtual three-dimensional space. The pattern texture is image data representing a pattern that is a basis when the potential field is generated, and is two-dimensional and binary image data.

  The virtual particle placement unit 102 sets a rectangular parallelepiped closed space in the virtual three-dimensional space. Further, the virtual particle arrangement unit 102 reads the particle data stored in the particle data storage unit 202, performs predetermined processing on the read particle data in accordance with an operation instruction from the user received by the input unit 300, and generates virtual particles. The shape is deformed, and a plurality of virtual particles are arranged in the closed space.

  The simulation execution unit 103 includes an external force calculation unit 111, a virtual particle growth unit 112, a position calculation unit 113, and a counter 114, and executes a simulation for growing virtual particles arranged in a closed space according to a growth pattern of skin cells.

  The external force calculation unit 111 calculates an external force that acts on each virtual particle arranged in the closed space. Here, the external force includes van der Waals force acting between molecules when one virtual particle is assumed as one molecule, repulsive force received from the above-described potential field, and gravity. In addition, when the external force acting on a certain virtual particle exceeds a predetermined value, the external force calculation unit 111 erases the virtual particle from the closed space and kills the virtual particle.

  Assuming one virtual particle as one skin cell, the virtual particle growth unit 112 increases the number of each virtual particle and increases the size of each virtual particle according to the growth pattern of the skin cell. Growing the particles.

  The position calculation unit 113 moves each virtual particle in a closed space by solving an equation of motion established in each virtual particle when the external force calculated by the external force calculation unit 111 is applied to each virtual particle. Calculate the position and velocity of each virtual particle. The counter 114 is a counter that measures the growth time of virtual particles. When the counter 114 increments the count value by 1, the virtual particle growth time elapses a predetermined time.

  The concavo-convex texture generation unit 104 obtains the distance between the virtual particle grown by the simulation execution unit 103 and the surface on one of the six surfaces constituting the closed space, and projects the virtual particle onto the surface. A surface is obtained, and height data is given to the surface based on the obtained projection surface, the virtual particle, and the distance between the surfaces to generate an uneven texture. Further, the uneven texture generation unit 104 stores the uneven texture in the uneven texture storage unit 203 as necessary.

  The rendering unit 105 reads a virtual three-dimensional model stored in advance in the three-dimensional model storage unit 204, and the uneven texture generated by the uneven texture generation unit 104 or the uneven texture storage unit 203 for the read virtual three-dimensional model. Rendering using the uneven texture stored in is performed.

  The display control unit 106 causes the display unit 400 to display the virtual three-dimensional model rendered by the rendering unit 105. In addition, the display control unit 106 reads a plurality of pattern textures from the pattern texture storage unit 201 and causes the display unit 400 to display a list on the display unit 400 in order to allow the user to select a pattern texture. Further, the display control unit 106 reads out the particle data stored in the particle data storage unit 202 and causes the display unit 400 to display the virtual particles in order to allow the user to set the shape of the virtual particles. Further, the display control unit 106 causes the display unit 400 to display the uneven texture generated by the uneven texture generation unit 104 or the uneven texture stored in the uneven texture storage unit 203.

  The storage unit 200 includes the external storage device 5 illustrated in FIG. 1 and the like, and includes functions of a pattern texture storage unit 201, a particle data storage unit 202, an uneven texture storage unit 203, and a three-dimensional model storage unit 204. These functions are realized by the CPU 3 executing the uneven texture generation program.

  The pattern texture storage unit 201 stores image data representing a base pattern when a potential field is generated. The particle data storage unit 202 stores particle data representing the default shape of virtual particles. This particle data is three-dimensional shape data. The particle data storage unit 202 stores mass data indicating the mass per unit volume of the virtual particles.

  The uneven texture storage unit 203 stores one or more uneven textures generated by the uneven texture generation unit 104. The three-dimensional model storage unit 204 stores a virtual three-dimensional model created in advance by a user using known application software that generates a three-dimensional model.

  The input unit 300 includes the input device 1 shown in FIG. 1 and accepts various operation commands issued by the user. The display unit 400 includes the display device 6 shown in FIG. 1 and displays various images under the control of the display control unit 106.

  In the present embodiment, the virtual particle arrangement unit 102 corresponds to an example of a virtual particle arrangement unit. The potential field generation unit 101 corresponds to an example of a virtual object generation unit. The external force calculation unit 111 corresponds to an example of an interparticle force calculation unit, a repulsion force calculation unit, and a virtual particle killing unit. Further, the virtual particle growth unit 112 corresponds to an example of a virtual particle growth unit. The position calculation unit 113 corresponds to an example of a position calculation unit. The potential field corresponds to an example of a virtual object.

  Next, the operation of the uneven texture generating apparatus will be described using the flowchart of FIG. First, the potential field generation unit 101 sets a rectangular parallelepiped closed space in the virtual three-dimensional space (step S1). FIG. 4 is a diagram illustrating a closed space generated in the virtual three-dimensional space by the potential field generation unit 101. As shown in FIG. 4, x, y, and z axes that are orthogonal to each other are set in the virtual three-dimensional space. Virtual gravity is acting in the -z direction. Note that the virtual three-dimensional space may be represented by another coordinate system (for example, a polar coordinate system) instead of the orthogonal coordinate system of the x, y, and z axes.

  The origin O, which is the intersection of the x, y, and z axes, is set at the lower left vertex of the closed space CS. Further, each side constituting the closed space CS is set in parallel with any one of the x, y, and z axes. Here, although the length of each side constituting the closed space CS is determined in advance, the potential field generation unit 101 determines the length of the closed space CS according to the operation command received from the user by the input unit 300. You may change suitably. In addition, the potential field generation unit 101 may adopt a shape other than a rectangular parallelepiped, for example, a sphere, a cube, or the like as the shape of the closed space CS.

  In step S2 shown in FIG. 3, the potential field generation unit 101 generates a potential field according to the pattern texture selected by the user. FIGS. 5A and 5B are diagrams showing examples of pattern textures. As shown in FIGS. 5A and 5B, the pattern texture is a rectangular image in which a long and narrow stripe pattern is represented. The pattern texture shown in (a) is composed of a single line meandering in the vertical direction and a line branched from two points of the line. The pattern texture shown in (b) is composed of three streaks arranged so as to spread concentrically. The pattern texture shown in FIGS. 5A and 5B is a binary image, and pixels constituting the stripe are represented by “1”, for example, and pixels constituting the background other than the stripe are “0”, for example. It is represented by

  In addition, the pattern texture shown to Fig.5 (a), (b) is only an example, You may employ | adopt the thing of another pattern. Further, an image created by the user using drawing software may be adopted as the pattern texture.

  The potential field generation unit 101 performs a filter process using a filter (for example, a Gaussian filter) that smoothes an image on the pattern texture selected by the user, and the pattern texture is set to each pixel having 0 to 255, for example. After conversion into a multi-valued image represented by 256 gradations, height data proportional to the number of gradations is given to each pixel. Thereby, the pattern texture is converted into three-dimensional image data.

  Next, the potential field generation unit 101 pastes the pattern texture converted into the three-dimensional image data on the inside of the surface on the XY plane (hereinafter referred to as the bottom surface BS) of the closed space CS shown in FIG. 4 by, for example, texture mapping. wear. As a result, as shown in FIG. 4, a potential field PF composed of streaky ridges and a plane parallel to the XY plane is formed on the bottom surface BS.

  In step S3 shown in FIG. 3, the virtual particle placement unit 102 reads shape data representing the default shape of the virtual particles P stored in the particle data storage unit 202, and places it in the closed space CS according to an operation command from the user. The number and position of the virtual particles P to be determined are determined, and the virtual particles P are arranged in the closed space CS by deforming the shape of the virtual particles P.

  Here, as the number of virtual particles P arranged in the closed space CS, for example, a value determined based on the number per unit volume of skin cells immediately after the birth of an animal such as a human and the volume of the closed space CS is adopted. can do. However, this value is appropriately changed according to an operation command from the user.

  The default shape of the virtual particle P is an ellipsoid in which the shorter two principal axes of the three principal axes have the same length. Hereinafter, of the three main axes of the ellipsoid, one long main axis is referred to as a long axis, and the remaining two main axes having the same length are referred to as short axes. Predetermined default values are adopted for the lengths of the major and minor axes of the ellipsoid. However, this default value is appropriately changed according to an operation command from the user. Further, a sphere may be adopted as the default shape of the virtual particle P. Further, the three main axes of the ellipsoid may have different lengths. Furthermore, an ellipsoid and a sphere may be mixed and arranged in the closed space.

  The virtual particle arrangement unit 102 uses a predetermined probability density function (for example, a normal distribution), a random number, or the like with respect to the default values of the major axis and the minor axis, or the lengths of the major axis and the minor axis changed by the user. By giving a certain variation, the length of the short axis and the long axis of each virtual particle P arranged in the closed space CS is determined, and the shape of the virtual particle P is changed. In addition, when it replaces with an ellipsoid and a sphere is employ | adopted, the user can change the shape of the virtual particle P by setting the radius of a sphere.

  Then, the virtual particle placement unit 102 does not overlap the virtual particles P in the closed space CS, the bottom surface BS is regarded as the skin surface, and the skin cell when the z direction is regarded as the skin depth direction. Virtual particles P are arranged according to the distribution. FIG. 4 shows the closed space CS immediately after the virtual particle placement unit 102 places the virtual particles P in the closed space CS. As shown in FIG. 4, it can be seen that a plurality of virtual particles P with moderately varying sizes are arranged in the closed space CS so as not to overlap. Here, the virtual particle arrangement unit 102 may arrange the virtual particles P so that the major axis directions of the virtual particles P are parallel to each other, or the virtual particles P may be appropriately dispersed by varying the major axis direction. May be arranged.

In step S4 shown in FIG. 3, the counter 114 sets the count value to i = 0 and initializes the growth time of the virtual particles P. In step S <b> 5, the external force calculation unit 111 calculates van der Waals forces acting on each virtual particle P using equation (1).
f (w) = K ₀ / l ₀ (5/4 · w ³ −19 / 8 · w ² +9/8) (1)
However,
f (w): van der Waals force K ₀ : spring coefficient w = l / l ₀ for determining attractive force and repulsive force between virtual particles
l: Distance l ₀ (P _i , P _j ) = 1/2 (d (P _i ) + d (P _j )) between the center of virtual particle P _{i and} the center of virtual particle P _j
P _i : i-th virtual particle P _j : j-th virtual particle d (P): length of major axis of virtual particle P

FIG. 6 is a graph showing the van der Waals force of equation (1), where the vertical axis indicates f (w) and the horizontal axis indicates w. As shown in FIG. 6, f (w) takes a positive value when w is in the range from 0 to 1. This is because when the virtual particle P _i, is P _j are overlapped as shown in FIG. 7 (b), shows that the repulsive force acts on the virtual particle P _i, P _j.

Further, f (w) takes a value of 0 when w is 1. This shows that when the virtual particles P _i and P _j are in contact with each other, as shown in FIG.

Further, f (w) takes a negative value when w is in the range of 1 to about 1.3. As shown in FIG. 7A, when virtual particles P _i and P _j are present within a certain distance range, an attractive force acts on the virtual particles P _i and P _j . . Further, f (w) takes a positive value when w is larger than 1.3. This indicates that repulsive force acts when the virtual particles P _i and P _j are separated by a certain distance or more.

In step S <b> 6 illustrated in FIG. 3, the external force calculation unit 111 calculates the constraint force FS from the potential field PF that acts on each virtual particle P. FIG. 8 is a diagram illustrating the constraint force FS acting on the virtual particle P. In addition, the diagonal slanting line shown in FIG. 8 shows the cross section of the potential field PF. External force calculation unit 111, a center O1 of the virtual particle _{P i,} obtains a straight line L1 connecting the potential field PF in the shortest distance, determining the intersection O2 of the straight line L1 and the potential field PF. Next, determine the normal vector V1 intersection O2, the force multiplied by a predetermined constant to a normal vector V1 determined, determined as the constraint force FS _i acting on virtual particle P _i. Here, as a predetermined constant, for example, can be employed mass of virtual particles P _i, may be employed magnitude of the gravitational acceleration as the magnitude of the normal vector V1.

In the case of the virtual particle P _k , since the intersection of the straight potential field PF connecting the center and the potential field PF with the shortest distance exists on the XY plane, the virtual particle P _k has the constraint force FS _{k in the} z direction. Will receive. However, since the virtual particle P _k receives the gravity FG _{k in the} −z direction, the constraint force FS _k and the gravity FG _k are canceled, and only the van der Waals force f from other virtual particles P is received. Become. As in the case of the virtual particle P _k , the virtual particle P _j is canceled because the constraint force FS _j and the gravity FG _j are directed in opposite directions, and only the van der Waals force f from the other virtual particles P is canceled. Will receive.

Therefore, the virtual particles P _i located in the vicinity of the slope of the raised object on the potential field PF are moved away from the raised object by the constraint force FS _i from the potential field PF.

  In step S <b> 7 shown in FIG. 3, the external force calculation unit 111 calculates the mass of each virtual particle P, and multiplies the calculated mass by the gravitational acceleration that acts in the −z direction, whereby the gravity FG that acts on each virtual particle P. Ask for. Here, the external force calculation unit 111 calculates the volume of the virtual particle P from the lengths of the major axis and the minor axis of the virtual particle P, and multiplies this volume by the mass data stored in the particle data storage unit 202 to obtain a virtual The mass of the particle P is determined.

  In step S <b> 8, the external force calculation unit 111 combines the van der Waals force f received by the virtual particle P from the other virtual particle P, the constraint force FS received from the potential field PF, and the gravity FG to act on the virtual particle P. The external force Fo is determined, and it is determined whether or not the magnitude of the external force Fo exceeds a predetermined value. Then, the virtual particles P to which the external force Fo exceeding the predetermined value acts are erased from the closed space CS, and the virtual particles P are killed. As this predetermined value, a value determined in advance based on the magnitude of pressure for killing actual skin cells is adopted.

  In step S9, the counter 114 increments the count value i by 1 and advances the virtual particle growth time by a predetermined time.

  In step S10, the position calculation unit 113 obtains the growth time t of the virtual particle P from the count value i, and solves the equation of motion shown in the equation (2) using the Runge-Kutta method, whereby the virtual particle P at the growth time t is obtained. Find the position and speed of. Note that the position calculation unit 113 may calculate the position and velocity of the virtual particle P using the Euler method or the like instead of the Runge-Kutta method.

但し
ｍ_ｉ：仮想粒子Ｐ_ｉの質量
ｘ_ｉ：仮想粒子Ｐ_ｉの位置
ｃ：閉空間ＣＳの粘性係数
ｔ：成長時間
ｆ_ｉ：仮想粒子Ｐ_ｉに作用するファンデルワールス力
ＦＳ_ｉ：仮想粒子Ｐ_ｉに作用する制約力
ＦＧ_ｉ：重力

However _{m i:} mass _{x i} of the virtual particles _{P i:} position of the virtual particles _{P i} c: viscosity coefficient of the closed space CS t: growth time _{f i:} virtual particle _{P i} Van der Waals forces acting on FS _i: virtual particle constraints force acting on the P _i FG _i: gravity

Here, x _i , f _i , FS _i , and FG _i are each a three-dimensional vector composed of x, y, and z components. As the viscosity coefficient c, a value determined in advance based on the viscosity coefficient of the cytoplasm of actual skin cells is employed.

  In step S11, the virtual particle growth unit 112 uses the function shown in Expression (3) indicating the actual increase in the size of the skin cell to determine the lengths of the major axis and the minor axis of the virtual particle P in the closed space CS. The virtual particle P is enlarged by increasing the height.

但し、
ＣＳ（ｃｕｒｒｅｎｔ＿ｓｉｚｅ）：成長時間ｔにおける仮想粒子Ｐの短軸及び長軸の長さ
ＩＳ（ｉｎｉｔｉａｌ＿ｓｉｚｅ）：仮想粒子配置部１０２により閉空間ＣＳに配置されたときの仮想粒子Ｐの短軸及び長軸の長さ
ｒ：成長率
ｔ：成長時間

However,
CS (current_size): Length of short axis and long axis of virtual particle P at growth time t IS (initial_size): short axis and long axis of virtual particle P when arranged in closed space CS by virtual particle arrangement unit 102 Length r: growth rate t: growth time

  Here, the growth rate r is a value determined in advance based on the actual increase rate of the skin cell size. In step S12, the virtual particle growth unit 112 is represented by a sigmoid curve, and the virtual particle newly added to the closed space CS is added using the function shown in Expression (4) representing the change over time of the actual increase in skin cells. The number of particles P (the number of increased virtual particles P) is obtained, the position where the added virtual particles P are arranged is obtained, and new virtual particles P are born in the closed space CS.

但し、
ＮＯＢ（ｎｕｍｂｅｒ＿ｏｆ＿ｂｉｒｔｈ）：新たに追加する仮想粒子の数
ａ，ｋ：定数
ｔ：成長時間
ｔ０：式（４）に示す関数の変曲点

However,
NOB (number_of_birth): number of newly added virtual particles a, k: constant t: growth time t0: inflection point of function shown in equation (4)

  FIG. 9 is a graph of the function shown in Expression (4), where the vertical axis indicates the number of newly added virtual particles, and the horizontal axis indicates the growth time. As shown in FIG. 9, it can be seen that the number of newly added virtual particles gradually decreases as the growth time t increases. It can also be seen that an inflection point exists at the time when the growth time t is t0. It can also be seen that t0 is about half of the growth time until the number of increase of the virtual particles P becomes almost zero.

  In step S13 shown in FIG. 3, the counter 114 determines whether or not the count value i has reached N (N is a positive integer) corresponding to the simulation end time, and the count value i is set to N. If it is determined that it has become (YES in S13), the process proceeds to step S14. On the other hand, when the counter 114 determines that the count value i is not N (NO in S13), the process returns to step S5. Here, the value of N is appropriately changed according to an operation command from the user.

  As described above, until the count value i becomes N, the processes from Steps S5 to S13 are repeatedly executed, and the simulation for growing the virtual particles P in the closed space CS is executed. FIG. 10 is a diagram illustrating the closed space CS at the end of the simulation. As shown in FIG. 10, the size and number of virtual particles P existing in the closed space CS are increased compared to FIG. 4 showing the closed space CS at the start of simulation, and the virtual particles P grow in the skin cells. You can see that it is growing according to the pattern.

  Moreover, it turns out that the virtual particle P located in the vicinity of the slope of the raised object of potential field PF is arrange | positioned away from the raised object by the constraint force FS from potential field PF.

  In step S14 shown in FIG. 3, the uneven texture generating unit 104 generates an uneven texture by projecting virtual particles P onto the bottom surface BS. FIG. 11 is a diagram illustrating a process in which the uneven texture generation unit 104 generates an uneven texture. First, the uneven texture generating unit 104 obtains a distance H between the center O1 of the virtual particle P and the bottom surface BS as shown in (a). Next, as shown in (b), the virtual particle P is projected onto the bottom surface BS, and the projection surface S1 of the virtual particle P formed on the bottom surface BS is obtained. Then, as shown in (c), the projection surface S1 and the distance H are connected by a Gaussian curved surface, height data is given to the projection surface S1, and an uneven texture is generated. Here, an ellipsoid may be used instead of the Gaussian curved surface.

  FIG. 12 is a diagram illustrating an example of the uneven texture generated by the uneven texture generating apparatus. (A), (c), and (d) are generated without generating the potential field PF in the closed space CS. (B) shows the uneven texture generated when the potential field PF is generated in the closed space CS.

  It can be seen that the uneven texture shown in (a) has a larger variation in the size of the wrinkle diameter than the uneven texture shown in (c). This is due to the fact that the virtual particle arrangement unit 102 increases the variation in the shape of the virtual particles P and arranges the virtual particles P in the closed space CS. Moreover, it can be seen that the uneven texture shown in (d) has a larger number of wrinkles than the uneven texture shown in (a) to (c). This is because the virtual particle placement unit 102 increases the number of virtual particles P and places them in the closed space CS, or lengthens the simulation time.

  Moreover, since the uneven texture shown in (b) forms the potential field PF generated based on the pattern texture shown on the left side in the closed space CS, and the virtual particles P are grown, on the right side of (b) As shown, it is understood that the texture is formed so as to avoid the streak portion indicated by the pattern texture.

  FIG. 13 is a diagram illustrating a rendering result when the uneven texture generated by using the uneven texture generating apparatus is bump-mapped on the dashboard of the automobile and a virtual three-dimensional model of the interior of the automobile is rendered. As shown in FIG. 13, it is understood that the texture on the dashboard surface is realistically reproduced by rendering using the three-dimensional model generated by the texture generation apparatus.

  As described above, according to the uneven texture generating device, the number and size of the virtual particles P arranged in the closed space CS are increased according to the growth pattern of the animal skin. Van der Waals force f, gravity FG, and constraint force FS act on each virtual particle P, and each time each virtual particle P grows for a certain period of time, these forces are calculated.

  In addition, the motion equation of each virtual particle P when the van der Waals force f, gravity FG, and constraint force FS are given to each virtual particle P is calculated each time the virtual particle P grows for a certain time using the Runge-Kutta method. By solving the above, the position and velocity of each virtual particle P are calculated. And the uneven | corrugated texture is produced | generated by projecting the virtual particle P grown for the predetermined time on the bottom face BS.

  Here, the virtual particles P are projected onto the bottom surface BS. Since the virtual particles P are grown according to the growth pattern of the living body skin, the texture formed on the surface of the bottom surface BS is a feature of the living body skin. Will be incorporated. As a result, it is possible to generate an uneven texture that realistically represents the characteristics of the skin of a living thing.

(Summary of the present invention)
(1) The uneven texture generation program according to the present invention is an uneven texture generation program for generating an uneven texture, which sets a closed space in a virtual three-dimensional space, and has a predetermined mass and a predetermined size in the set closed space. Virtual particle placement means for arranging a plurality of virtual particles having a thickness, and a growth pattern of biological skin cells, and the number of virtual particles arranged by the virtual particle placement means and the size of each virtual particle Virtual particle growth means for increasing and growing each virtual particle in the closed space; and interparticle force calculation means for calculating the interparticle force acting between the virtual particles determined based on the distance between the virtual particles. And position calculating means for calculating the position of each virtual particle by solving a motion equation of each virtual particle when the interparticle force is applied to each virtual particle, and a virtual in a closed space Based on the position and size of the child, it is characterized in causing a computer to function as uneven texture generating means for generating an uneven texture.

  The uneven texture generating device according to the present invention is an uneven texture generating device that generates an uneven texture, wherein a closed space is set in a virtual three-dimensional space, and a predetermined mass and a predetermined size are set in the set closed space. Virtual particle placement means for placing a plurality of virtual particles having the same, and the growth pattern of biological skin cells are simulated to increase the number of virtual particles placed by the virtual particle placement means and the size of each virtual particle Virtual particle growth means for growing each virtual particle in the closed space; and interparticle force calculation means for calculating an interparticle force acting between the virtual particles determined based on a distance between the virtual particles; Position calculation means for calculating the position of each virtual particle by solving the equation of motion of each virtual particle when the interparticle force is applied to each virtual particle, and the position and position of the virtual particle in the closed space Based on size and is characterized in that it comprises a concave-convex texture generating means for generating an uneven texture.

  According to these configurations, the number and size of the virtual particles in the closed space are increased according to the growth pattern of the skin cells of the organism. An interparticle force determined based on the distance between the virtual particles is acting on each virtual particle existing in the virtual three-dimensional space, and the interparticle force acting on each virtual particle is calculated.

  Further, the position of each virtual particle is calculated by solving the equation of motion of each virtual particle when an interparticle force is applied to each virtual particle as an external force. And the uneven | corrugated texture is produced | generated based on the position and magnitude | size of the virtual particle in closed space.

  That is, when the closed space is assumed to be skin tissue, the size and number of virtual particles are determined according to the growth pattern of the skin cells contained in the skin tissue, and the uneven texture is determined based on the position and size of the virtual particles. Since it is generated, it is possible to generate an uneven texture that more realistically represents animal skin characteristics.

  (2) Further, in the above configuration, a virtual object generating means for generating a virtual object that causes a repulsive force on each virtual particle in the closed space based on an operation command from a user, and the virtual particle grows for a certain period of time. Each time, the computer is further functioned as a repulsive force calculating means for calculating a repulsive force from the virtual object acting on each virtual particle, and the position calculating means includes the repulsive force calculated by the repulsive force calculating means and the interparticle force. Is preferably applied to each virtual particle to solve the equation of motion.

  According to this configuration, the virtual particles are moved away from the virtual object by the repulsive force from the virtual object, so that the virtual particles can be appropriately dispersed.

  (3) In the above configuration, the computer further functions as a texture storage unit that stores one or more types of textures representing a predetermined pattern, and the virtual object generation unit stores the texture stored in the texture storage unit. It is preferable to select any one of the textures according to an operation command from the user and generate the virtual object based on the selected texture pattern.

  According to this configuration, when the user selects a texture, a virtual object is generated based on the pattern represented by the texture, and each virtual particle is moved by the repulsive force from the virtual object. An uneven texture that represents a pattern can be generated.

  (4) Moreover, in the said structure, while the said closed space is a hexahedron, the said uneven | corrugated texture production | generation means calculates | requires the distance of one surface with the said hexahedron, and each virtual particle, and the said surface of each virtual particle It is preferable that a projection surface is obtained, and height data is given to the surface based on the obtained distance and projection surface to generate an uneven texture.

  According to this configuration, since the virtual particles are projected onto one surface of the hexahedron to generate the uneven texture, the uneven texture representing the unevenness appearing on the skin surface when this surface is regarded as the skin surface of a living organism. Can be generated.

  (5) Further, in the above configuration, virtual particles in which the resultant force between the interparticle force calculated by the interparticle force calculating unit and the repulsive force calculated by the repulsive force calculating unit is larger than a predetermined value are removed from the closed space. It is preferable to further include virtual particle killing means for killing the virtual particles.

  According to this configuration, it is possible to grow virtual particles that exist in a closed space taking into consideration the characteristics of the skin of an organism that will die when subjected to a certain force, and to create an uneven texture that more realistically represents the characteristics of the skin. Can be generated.

  (6) Further, in the above configuration, the virtual particle growth means may increase the number of virtual particles using a predetermined function indicating a change with time of the number of skin cells expressed based on a sigmoid curve. preferable.

  According to this configuration, since the number of virtual particles is increased by using a predetermined function indicating a change with time of the number of skin cells expressed based on the sigmoid curve, the number of virtual particles is increased to the actual growth of skin cells. Can be increased according to the pattern. As a result, it is possible to generate an uneven texture that more realistically represents skin characteristics.

  (7) Further, in the above configuration, the virtual particle growth means increases the size of the virtual particle using a predetermined function indicating a change with time of the size of the skin cell expressed based on an exponential function. It is preferable.

  According to this configuration, the size of the virtual particle is increased by using a predetermined function that indicates a change with time in the size of the skin cell expressed based on the exponential function. It can be increased according to the growth pattern of skin cells. As a result, it is possible to generate an uneven texture that more realistically represents skin characteristics.

  (8) In the above configuration, the interparticle force calculation means preferably calculates the interparticle force using a predetermined function indicating Van der Waals force.

According to this configuration, since van der Waals force is applied to the virtual particles, it is possible to generate an uneven texture that more realistically represents the growth pattern of skin cells.

Claims (9)

An uneven texture generating program for generating an uneven texture,
Virtual particle placement means for setting a closed space in the virtual three-dimensional space and placing a plurality of virtual particles having a predetermined mass and a predetermined size in the set closed space;
Virtual particles for simulating a growth pattern of biological skin cells, increasing the number of virtual particles arranged by the virtual particle arrangement means and the size of each virtual particle, and growing each virtual particle in the closed space Growth means,
An interparticle force calculating means for calculating an interparticle force acting between the virtual particles determined based on the distance between the virtual particles;
Position calculating means for calculating the position of each virtual particle by solving the equation of motion of each virtual particle when the interparticle force is applied to each virtual particle;
An uneven texture generation program that causes a computer to function as uneven texture generation means for generating an uneven texture based on the position and size of virtual particles in a closed space. Virtual object generating means for generating a virtual object in which repulsive force is applied to each virtual particle in the closed space based on an operation command from a user;
Each time the virtual particles grow for a certain period of time, the computer further functions as a repulsive force calculating means for calculating repulsive force from the virtual object acting on each virtual particle,
2. The uneven texture generating program according to claim 1, wherein the position calculating means solves the equation of motion by applying the repulsive force calculated by the repulsive force calculating means and the interparticle force to each virtual particle. Further causing the computer to function as texture storage means for storing one or more types of textures representing a predetermined pattern;
The virtual object generation means selects any one of the textures stored in the texture storage means according to an operation command from a user, and generates the virtual object based on the selected texture pattern. The program for generating uneven texture according to claim 2, wherein: The closed space is a hexahedron,
The concavo-convex texture generation means obtains a distance between one surface of the hexahedron and each virtual particle, obtains a projection surface of each virtual particle on the surface, and based on the obtained distance and the projection surface, 4. The uneven texture generating program according to claim 3, wherein height data is given to the surface to generate an uneven texture.   A virtual particle that kills a virtual particle by removing from the closed space a virtual particle whose resultant force between the interparticle force calculated by the interparticle force calculating unit and the repulsive force calculated by the repulsive force calculating unit is larger than a predetermined value. The uneven texture generating program according to claim 2, further causing a computer to function as the particle killing means.   The virtual particle growing means increases the number of virtual particles in a closed space using a predetermined function indicating a change with time of the number of skin cells expressed based on a sigmoid curve. The uneven | corrugated texture production | generation program in any one of 1-5.   The virtual particle growth means increases the size of the virtual particle using a predetermined function indicating a change with time of the size of the skin cell expressed based on an exponential function. The uneven | corrugated texture production | generation program in any one of.   The uneven particle texture generation program according to any one of claims 1 to 7, wherein the interparticle force calculation means calculates the interparticle force using a predetermined function indicating Van der Waals force. An uneven texture generating apparatus for generating an uneven texture,
Virtual particle placement means for setting a closed space in the virtual three-dimensional space and placing a plurality of virtual particles having a predetermined mass and a predetermined size in the set closed space;
Virtual particles for simulating a growth pattern of biological skin cells, increasing the number of virtual particles arranged by the virtual particle arrangement means and the size of each virtual particle, and growing each virtual particle in the closed space Growth means,
An interparticle force calculating means for calculating an interparticle force acting between the virtual particles determined based on the distance between the virtual particles;
Position calculating means for calculating the position of each virtual particle by solving the equation of motion of each virtual particle when the interparticle force is applied to each virtual particle;
The uneven | corrugated texture production | generation apparatus provided with the uneven | corrugated texture production | generation means which produces | generates an uneven | corrugated texture based on the position and magnitude | size of the virtual particle in closed space.

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