JP2019031061A - Color signal processing unit, three-dimensional molding apparatus and color signal processing program - Google Patents

Abstract

To appropriately express a gloss feeling of a surface of a three-dimensional object in a configuration in which only one color ink is discharged for one voxel.SOLUTION: A color signal processing unit has second color signal generating means 158 for generating a second color signal including a base color signal (A signal) representing a base color component constituting an internal region other than a surface region of a three-dimensional object and a second color component signal representing a second color component (CMY signal) constituting an output color from a first color signal representing a first color component (RGB), and transparent signal generating means 162 for generating a white signal (W signal) representing white color and a transparent signal (T signal) representing transparent color at a mixing ratio according to a magnitude of the base color signal (A signal).SELECTED DRAWING: Figure 6

Description

  The present invention relates to a color signal processing apparatus, a three-dimensional modeling apparatus, and a color signal processing program.

  A three-dimensional modeling apparatus that models a three-dimensional object by stacking cross-sectional shapes based on shape data of a three-dimensional model is known. For example, an optical modeling type three-dimensional printer that forms a three-dimensional shape by forming and stacking cross-sectional shapes by discharging ultraviolet curable ink on a stage is known. In such a three-dimensional modeling apparatus, it is possible to form a three-dimensional object reflecting not only the shape but also the color by ejecting color ink onto a portion that becomes the surface of the three-dimensional object.

  In Patent Document 1, cyan (C), magenta (M), yellow (Y), and white (W) toners are used to form a color toner layer after covering the entire surface of a transparent sheet with a white toner layer. Thus, a method of manufacturing a three-dimensional structure with improved surface color gradation and color tone is disclosed. In this technique, CMY toners can be placed on one pixel or voxel in an overlapping manner.

  Patent Document 2 discloses modeling data obtained by applying error diffusion processing to a surface pixel aggregate corresponding to a surface portion of a modeled object in an apparatus that forms a three-dimensional modeled object by solidifying a three-dimensional modeled powder with a modeling liquid. A three-dimensional modeling data creation device is disclosed in which the vertical stripes of the color generated in the modeled object are suppressed. Also in this technique, CMYK toner can be placed on one pixel or voxel.

JP 2000-246804 A JP 2015-44299 A

  By the way, not only a configuration that expresses the surface color of a three-dimensional object by ejecting a plurality of colors of ink to one pixel or voxel, but only one color of ink per pixel or voxel due to the limitation of ink amount or the like. There are also configurations that can only discharge. Therefore, there is a need for a technique that can appropriately represent the surface color of a three-dimensional object in a configuration in which only one color of ink is ejected to one pixel or voxel.

  In the three-dimensional modeling apparatus, in order to appropriately express the surface color, it is necessary to appropriately express the glossiness, that is, the glossiness of the surface. However, if one of the white ink and the transparent ink is used in the technology using the white ink or the transparent ink in addition to the color ink, the glossiness of the surface may not be appropriately expressed. For example, when white ink is ejected in addition to color ink, light transmission to the formed object is blocked by the white ink, so light cannot reach the color ink in the deep part of the object, and the color of the object The concentration may become too low.

  According to the first aspect of the present invention, the second color component signal representing the second color component constituting the output color from the first color signal representing the first color component and the interior other than the surface region of the three-dimensional object A second color signal generating means for generating a second color signal including a base color signal representing a base color component constituting a region, and a white signal representing white at a mixing ratio according to the magnitude of the base color signal; A color signal processing apparatus comprising: a transparent signal generating unit that generates a transparent signal representing transparency.

  According to a second aspect of the present invention, the first color signal is set for each pixel, and the transparent signal generating means sets the ratio of the mixture of the white signal and the transparent signal to the distance from the object surface of the pixel. The color signal processing apparatus according to claim 1, wherein the color signal processing apparatus is set accordingly.

  The invention according to claim 3 is characterized in that the transparent signal generation means decreases the ratio of the mixture of the transparent signal with respect to the white signal in accordance with the distance of the pixel from the object surface. The color signal processing apparatus according to claim 1.

  The invention according to claim 4 is characterized in that the transparent signal generation means increases the ratio of the mixture of the transparent signal with respect to the white signal in accordance with the distance of the pixel from the object surface. The color signal processing apparatus according to claim 1.

  According to a fifth aspect of the present invention, the transparent signal generation means makes the white signal constant regardless of the distance of the pixel from the object surface, and increases the transparent signal according to the distance of the pixel from the object surface. The color signal processing apparatus according to claim 2, wherein:

  According to a sixth aspect of the invention, there is provided ink color selection means for selecting a color of ink to be ejected in accordance with a ratio of the white color signal and the transparent signal constituting the second color component signal and the base color signal. The color signal processing apparatus according to claim 1, wherein the color signal processing apparatus is a color signal processing apparatus.

  A seventh aspect of the present invention is a three-dimensional modeling apparatus including the color signal processing apparatus and further including an ink discharge unit that discharges ink of a color selected by the ink color selection unit.

  According to an eighth aspect of the present invention, the computer is configured to output from the first color signal representing the first color component, the second color component signal representing the second color component constituting the output color, and the first color signal. A second color signal generating means for generating a second color signal including a base color signal corresponding to the magnitude, a white signal representing white at a mixing ratio corresponding to the magnitude of the base color signal, and a transparency representing transparency A color signal processing program which functions as a transparent signal generating means for generating a signal.

  According to the first and eighth aspects of the invention, it is possible to generate a color signal that more appropriately represents the glossiness of the surface of the three-dimensional object than when one of the white ink and the transparent ink is used.

  According to the second, third, and fourth aspects of the invention, the glossiness of the surface of the three-dimensional object can be more appropriately expressed as compared with the case where the distance from the object surface is not considered.

  According to the fifth aspect of the present invention, when the ratio of the mixture of the white signal and the transparent signal is set according to the distance from the object surface of the pixel, the ratio is changed when the white signal and the transparent signal are changed complementarily. Thus, it is possible to increase parameters that can be adjusted to generate a color signal that appropriately represents the glossiness of the surface of the three-dimensional object.

  According to the sixth aspect of the present invention, it is possible to select ink that appropriately expresses the glossiness of the surface of the three-dimensional object in a configuration in which only one color of ink is ejected to one pixel or voxel.

  According to the invention described in claim 7, it is possible to form a three-dimensional object in which the glossiness of the surface is appropriately expressed.

It is a figure which shows the structure of the three-dimensional modeling apparatus in embodiment of this invention. It is a figure which shows the structure of the modeling part in embodiment of this invention. It is a figure which shows the structure of the ink head in embodiment of this invention. It is a figure which shows the structure of the control part in embodiment of this invention. It is a flowchart which shows the color signal process and modeling process in embodiment of this invention. It is a functional block diagram of the three-dimensional modeling apparatus in embodiment of this invention. It is a figure explaining the voxelization process in embodiment of this invention. It is a figure which shows the structural example of the 2nd color signal in 1st Embodiment. It is a figure which shows the change of the gradation expression by the ratio of the ink of white (W) and transparent color (T). It is a figure explaining control of the glossiness of the surface of a three-dimensional object. It is a figure which shows another example of a structure of the 2nd color signal in 1st Embodiment. It is a figure which shows another example of a structure of the 2nd color signal in 1st Embodiment. It is a figure which shows the structural example of the 2nd color signal in 2nd Embodiment. It is a figure which shows another example of a structure of the 2nd color signal in 2nd Embodiment.

<First Embodiment>
As shown in FIG. 1, the three-dimensional modeling apparatus 100 according to the first embodiment includes a modeling unit 102 and a control unit 104. The control unit 104 generates modeling data considering the surface color from the three-dimensional data representing the three-dimensional object, and controls the modeling unit 102 based on the modeling data to model the three-dimensional object.

  1 shows a configuration in which the modeling unit 102 and the control unit 104 are directly connected, but the modeling unit 102 and the control unit 104 may be connected via an information communication network such as the Internet.

  As shown in FIG. 2, the modeling unit 102 includes a modeling table 10, a stage 12, an ink tank 14, an ink head 16, and a head driving unit 18. The modeling table 10 is a component that serves as a foundation for mechanically supporting the modeling unit 102. On the modeling table 10, a stage 12, an ink tank 14, an ink head 16, and a head driving unit 18 are arranged.

  The stage 12 is a component serving as a table for forming a modeled object. The upper surface of the stage 12 is preferably a shape suitable for forming a modeled object, for example, a flat surface. In the present embodiment, the vertical direction (upward direction) is described as the Z-axis direction for convenience. The stage 12 includes a stage driving mechanism. The stage 12 can be moved up and down along the Z-axis direction according to a control signal from the control unit 104.

  The ink tank 14 is a component for storing ink for constituting a three-dimensional object to be shaped. In the present embodiment, since the modeled object is a three-dimensional object having a color surface, the ink tank 14 includes an ink storage unit that stores ink of color components constituting the output color. In the present embodiment, the color components constituting the output color are cyan (C), magenta (M), and yellow (Y). However, it is not limited to this. The ink tank 14 also includes an ink storage unit that stores base color ink. The base color is the color of ink that forms an internal region other than the surface region of the three-dimensional object to be shaped. The base color is preferably a bright achromatic color. Specifically, the base color ink may be white ink (W) and transparent ink (T). In this embodiment, it is assumed that the base color ink includes both white (W) and transparent ink (T).

  The ink head 16 is a component that discharges ink supplied from the ink tank 14. The ink head 16 includes a number of ink nozzles that can eject the color components constituting the output color and the base color ink. The ink head 16 is disposed on the stage 12. The ink tank 14 and the ink head 16 constitute an ink ejection unit.

  FIG. 3 shows a configuration example of the ink head 16. The ink head 16 includes a nozzle group 16A in which ink nozzles 16C, 16M, 16Y, 16W, and 16T corresponding to each color of CMYWT are arranged in the Y-axis direction. The ink head 16 has a nozzle array structure in which a plurality of nozzle groups 16A are arranged along the X-axis direction. It is preferable that the nozzle group 16 </ b> A is arranged as many as necessary to form a modeled object across the width of the stage 12 in the X-axis direction.

  Further, when the ink used in the modeling unit 102 is an ultraviolet curable type, the ultraviolet irradiation means 16 </ b> V may be provided in the ink head 16. As the ultraviolet irradiation means 16V, an ultraviolet lamp, an ultraviolet laser, or the like can be applied. The ultraviolet irradiation means 16V may be provided separately from the ink head 16. After the ink is ejected from the ink nozzles 16C, 16M, 16Y, 16W, and 16T, the ink can be cured by irradiating the ultraviolet rays from the ultraviolet irradiation means 16V.

  The head drive unit 18 is a component for moving the ink head 16 on the stage 12. The head drive unit 18 includes a rail 18a arranged along the Y-axis direction. Further, it may be configured to include a motor (not shown) for moving the ink head 16 along the rail 18a. The ink head 16 is supported by a rail 18a so as to be movable in the Y-axis direction, and is coupled to a motor via a driving member such as a ball screw. The head driving unit 18 can move the ink head 16 along the rail 18a, that is, along the Y-axis direction by rotating the motor in accordance with a control signal from the control unit 104. However, the configuration of the head drive unit 18 is not limited to this, and any configuration may be used as long as the ink head 16 can be moved relative to the stage 12 in order to form a three-dimensional object.

  The modeling unit 102 receives from the control unit 104 modeling data including position information of pixels (voxels: volume elements) constituting the three-dimensional object and color information of the voxels. The modeling unit 102 moves the stage 12 up and down to a position in the Z-axis direction corresponding to the position information received from the control unit 104, and moves the ink head 16 to a position in the Y-axis direction corresponding to the position information. Then, the ink of the color specified by the color information of the voxel is ejected from any one of the ink nozzles 16C, 16M, 16Y, 16W, and 16T in the X-axis direction corresponding to the position information.

  A three-dimensional object is represented by three-dimensional data including a group of voxels that are lattice units of volumes in the X-axis direction-Y-axis direction-Z-axis direction. The three-dimensional data has one layer for each voxel thickness along the X-axis-Y-axis plane. The modeling unit 102 ejects ink along the X-axis-Y-axis plane while moving the ink head 16 in the Y-axis direction. When modeling for one layer is completed, the stage 12 is moved downward along the Z-axis direction. Let me move on to the next layer. The modeling unit 102 models a three-dimensional object by repeating this.

  As shown in FIG. 4, the control unit 104 includes a processing unit 30, a storage unit 32, an input unit 34, an output unit 36, and a communication unit 38. The control unit 104 can be configured by a general computer. The processing unit 30 includes means for performing arithmetic processing such as a CPU. The processing unit 30 executes the color signal processing program stored in the storage unit 32 to realize the color signal processing in the present embodiment. Thereby, the control unit 104 functions as a color signal processing device. In addition, the control unit 104 executes a modeling process program stored in the storage unit 32 to output and control a signal that causes the modeling unit 102 to eject ink. The storage unit 32 includes storage means such as a semiconductor memory or a memory card. The storage unit 32 is connected to the processing unit 30 so as to be accessible, and stores a color signal processing program, a modeling processing program, and information necessary for the processing. The input unit 34 includes means for inputting information. The input unit 34 includes, for example, a keyboard, a touch panel, and a button that receive a command input from the user. The output unit 36 presents information regarding processing to the user. The output unit 36 can be, for example, a display that displays an image to the user. The communication unit 38 includes an interface for outputting information such as position information and color information to the modeling unit 102. Moreover, the communication part 38 may be provided with the interface for acquiring the three-dimensional data of the three-dimensional object used as modeling object from the outside via information communication networks, such as the internet.

  In the present embodiment, the control unit 104 is realized by executing a program in a general computer, but part or all of the control unit 104 may be realized by hardware such as an ASIC.

  Various programs such as a color signal processing program and a modeling processing program may be provided via the communication unit 38 or may be provided by a recording medium such as a CDROM.

  Hereinafter, with reference to the flowchart shown in FIG. 5, the modeling process of the three-dimensional object in this Embodiment is demonstrated. The control unit 104 executes the following process by executing the color signal processing program and the modeling process program. The three-dimensional modeling apparatus 100 functions as each unit shown in the functional block diagram of FIG. 6 by the following processing.

  In step S10, three-dimensional data acquisition processing is performed. The control unit 104 functions as the three-dimensional data acquisition unit 150 by the processing in this step. The processing unit 30 acquires three-dimensional data representing the outer shape of the three-dimensional object to be modeled via the input unit 34 or the communication unit 38. The acquired three-dimensional data is stored in the storage unit 32. The three-dimensional data includes three-dimensional object shape data designed by CAD or the like, or three-dimensional object shape data measured by a three-dimensional shape measuring instrument or the like.

  The three-dimensional data also includes color data (first color signal) of the surface of the three-dimensional object. In the present embodiment, the three-dimensional data includes color data representing the surface color of a three-dimensional object in an RGB color space composed of red (R signal), green (G signal), and blue (B signal) color components. Is included.

  In step S12, voxelization processing is performed. By the processing in this step, the control unit 104 functions as the voxelization processing unit 152. The processing unit 30 reads the three-dimensional data acquired in step S10 from the storage unit 32, and converts the three-dimensional data into voxel data. The voxel data is data representing a three-dimensional object represented by three-dimensional data as a set of normal lattice units (voxels) in a three-dimensional space. In the voxel data, each voxel includes information indicating the position of the voxel, information indicating whether or not a three-dimensional object defined by the three-dimensional data is configured, and information indicating a distance from the object surface.

  The voxelization process is performed as follows, for example. A three-dimensional space is divided into voxels having a shape and size as a unit of division. Then, data (for example, “1”) indicating that the three-dimensional object is configured is assigned to the voxels included in the space covered with the surface of the three-dimensional object, and three-dimensional is assigned to the voxels outside the space. Data (for example, “0”) indicating that the object is not configured is assigned. More specifically, for example, as shown in FIG. 7, the three-dimensional object 200 is cut out with the width of the voxel along the Z-axis direction. Furthermore, the inside of the cross-sectional shape of the object in the cut out X-axis-Y-axis plane is divided into a voxel width grid to obtain a voxel B. Then, data indicating that a three-dimensional object is configured is assigned to each voxel B. Further, the shortest distance from the surface of the three-dimensional object to the center point of the voxel B is calculated and assigned to each voxel B. Such processing is repeated along the Z-axis direction of the three-dimensional object, and voxel processing is performed by stacking voxel layers. The generated voxel data is stored in the storage unit 32.

  In step S14, color information is assigned to voxels. The control unit 104 functions as the color information assigning unit 154 by the processing in this step. The processing unit 30 assigns the color data (first color signal) included in the three-dimensional data to each voxel of the voxel data obtained in step S12. Among the voxels to which data indicating that a three-dimensional object is configured is assigned, the voxel (surface voxel) positioned on the surface of the three-dimensional object has color data (first color) of the surface position of the three-dimensional data. Signal). Here, the surface voxel means a voxel that is not completely covered with other voxels among the voxels constituting the object. Further, the color data of the voxel on the object surface closest to the voxel is assigned to the voxel (internal voxel) located inside the three-dimensional object. Here, the internal voxel means a voxel that is completely covered with other voxels among the voxels constituting the object.

  Note that color data may be assigned only to voxels within the reference distance D1 from the surface of the three-dimensional object, and a base color may be assigned to deep voxels exceeding the distance D1. That is, with the distance D1 as a threshold value, a surface color is assigned to a voxel located on the surface side of the distance D1, and a base color is assigned to a voxel located on the object inside of the distance D1. Further, the color data value assigned according to the distance of the voxel from the object surface may be weighted. For example, weighting is performed so that the surface color value decreases as the distance from the surface of the object increases, and the base color value increases. In addition, the value of the color data to be assigned may be weighted according to the deviation of the voxel position from the normal direction with respect to the object surface. For example, the value of color data weighted by the cosine value of the angle shifted from the normal direction of the voxel may be assigned to the voxel. Furthermore, these methods may be combined.

  In step S <b> 16, color space conversion processing is performed for converting the color data (first color signal) acquired as the three-dimensional data into color data for representing the output color output to the modeling unit 102. By this processing, the control unit 104 functions as the color space conversion unit 156. The three-dimensional data acquired in step S10 includes color data (first color signal) composed of a first color space composed of a first color component (RGB in the present embodiment). The output color output to the modeling unit 102 is represented by color data including a second color space composed of a second color component (CMY in the present embodiment) that can be expressed by the ink used in the modeling unit 102. The In this step, color space conversion processing from the first color space to the second color space is performed for each voxel to which color data is assigned in step S14.

  In the present embodiment, the output color is represented in a CMY color space composed of cyan (C signal), magenta (M signal), and yellow (Y signal) color components that can be expressed by the ink used in the modeling unit 102. Color data (color signal). However, the color components constituting the output color are not limited to these. For color space conversion from the RGB color space to the CMY color space, existing complementary color conversion processing or conversion processing using a 3D-LUT (three-dimensional lookup table) may be applied.

  In step S18, color data including a second color component signal representing the second color component from the color data converted into the second color space in step S16 and a base color signal corresponding to the magnitude of the first color signal ( A process for generating a second color signal) is performed. By this processing, the control unit 104 functions as the second color signal generation unit 158. In this embodiment, the base color (A) is used. That is, the processing unit 30 includes color data (CMY signal) converted to the second color space in step S16, including color data (C signal) representing a second color component and a base color signal (A signal). Conversion processing to a second color signal (CMYA signal) is performed.

First, the processing unit 30 generates an A signal from the CMY signal. The A signal can be obtained by Expression (1). Here, C, M, Y, and A indicate the magnitudes of the C signal, the M signal, the Y signal, and the A signal, respectively, and are real numbers from 0 to 1.
(Equation 1)
A = (1-C) (1-M) (1-Y) (1)

  As shown in Equation (1), the A signal is a value corresponding to the magnitudes of the C, M, and Y signals obtained by the color space conversion in step S16. Here, the C signal, the M signal, and the Y signal are obtained according to the magnitude of the first color signal (R signal, G signal, B signal) by color space conversion in step S16. Therefore, the A signal has a value corresponding to the magnitude of the first color signal.

  Further, the processing unit 30 causes the color data (C signal, M) of the second color component according to the A signal so that the color expressed by the first color signal is maintained in the second color signal including the A signal. Modified CMY data (C ′ signal, M ′ signal, Y ′ signal) obtained by correcting the signal and the Y signal) is generated. With this processing, the processing unit 30 functions as the second color signal correcting unit 160.

The corrected CMY data (C ′ signal, M ′ signal, Y ′ signal) can be obtained by Equation (2).
(Equation 2)
C '= C (1-M) (1-Y) + CM (1-Y) / 2 + C (1-M) Y / 2 + CMY / 3
M '= (1-C) M (1-Y) + CM (1-Y) / 2 + (1-C) MY / 2 + CMY / 3
Y '= (1-C) (1-M) Y + C (1-M) Y / 2 + (1-C) MY / 2 + CMY / 3 (2)

  Here, the A signal may be further modified. For example, the value of the A signal may be changed according to the distance of the voxel from the object surface. For example, when the value of the A signal is not changed according to the distance, as shown in FIG. 8, the value of the A signal calculated by the equation (1) is within the reference distance D1 from the surface of the three-dimensional object. The value of the A signal is maximum ("1") deeper than D1. In FIG. 8, the vertical axis indicates the ratio of each color signal (each color ink), and the horizontal axis indicates the distance (depth) from the object surface.

  In step S20, a process of generating a white signal (W signal) and a transparent signal (T signal) according to the base color signal (A signal) included in the second color signal generated in step S18 is performed. With this processing, the control unit 104 functions as the transparent signal generation unit 162.

Based on the A signal, the W signal and the T signal can be calculated based on Equation (3). Here, k is a real number satisfying 0 <k <1.
(Equation 3)
W = k x A
T = (1-k) x A (3)

  As a result, as shown in FIG. 8, regardless of the distance from the object surface, a W signal with a constant ratio k is generated according to the magnitude of the A signal, and a T signal with a ratio (1-k) is generated. The Thereby, by adjusting the ratio k, the ratio of voxels in which white (W) and transparent color (T) are used among the voxels constituting the object is adjusted, and the gloss of the color when viewed from the object surface is adjusted. A second color signal that appropriately expresses the feeling (glossiness) is generated.

  A voxel that is far from the object surface has less influence on color expression on the object surface. Therefore, only a W signal or a T signal may be assigned to a voxel that is a base material portion of an object having such a distance (for example, distance D1 in FIG. 8) or more.

  In step S22, a process for selecting the ink to be ejected is performed. By the processing in this step, the control unit 104 functions as the ink color selection unit 164. In the modeling unit 102 in the present embodiment, one ink of cyan (C), magenta (M), yellow (Y), white (W), and transparent color (T) is applied to one voxel from the ink head 16. It is set as the structure which discharges only. Therefore, the processing unit 30 selects ink to be ejected by the modeling unit 102 for each voxel based on the corrected CMY signal (C ′ signal, M ′ signal, Y ′ signal), the W signal, and the T signal. I do.

  The ink selection process is not particularly limited. In this embodiment, the ink selection rate selected from cyan (C), magenta (M), yellow (Y), white (W), and transparent color (T) is the C ′ signal, M ′ signal, and Y ′. It is preferable that the ink is selected so as to have a value corresponding to the ratio of the magnitudes of the signal, W signal, and T signal.

  For example, cyan (C) is selected when C ′ signal> a with respect to the reference value a generated by the sequence generator. If (C ′ signal + M ′ signal)> a, magenta (M) is selected. If (C ′ signal + M ′ signal + Y ′ signal)> a, yellow (Y) is selected. Also, when (C ′ signal + M ′ signal + Y ′ signal + W signal)> a, white (W) is selected. In other cases, the transparent color (T) is selected.

  Further, an ordered dither method may be applied. That is, a sequence (dither matrix) is applied as a reference value a for each voxel, cyan (C) is selected when C ′ signal> a, and magenta (M) when (C ′ signal + M ′ signal)> a. ), And when (C ′ signal + M ′ signal + Y ′ signal)> a, yellow (Y) is selected, and when (C ′ signal + M ′ signal + Y ′ signal + W signal)> a, white (W ) Is selected, otherwise the transparent color (T) is selected.

  Further, an error diffusion method (Error Diffusion) may be applied. In this method, a fixed value is used as the reference value a, but an error that occurs when an ink color is selected for a certain voxel is diffused in the selection process of surrounding voxels. Furthermore, ink may be selected for each voxel by the method disclosed in Japanese Patent Laid-Open No. 2006-295899.

  Further, a white noise method, a blue noise mask method, or the like may be applied. The white noise method is a method in which white noise (uniform random number) is applied as the reference value a for each voxel. In the blue noise mask method, the size of the dither matrix is increased so that the spatial frequency distribution of the dither matrix applied to the reference value a is equal to or higher than the spatial frequency at which the human visual sensitivity is low.

  In step S24, a slicing process for cutting out each layer to be modeled in the modeling unit 102 is performed. By this processing, the control unit 104 functions as the slice processing unit 166. Similar to the slicing in the Z-axis direction in the voxelization process in step S12, the processing unit 30 slices the voxels constituting the three-dimensional object along the Z-axis direction and cuts out one layer for each voxel. That is, the ink head 16 of the modeling unit 102 extracts a layer that can be ejected in one scan. For each layer, the ink color selected for each voxel included in the layer is read from the storage unit 32 and is used as modeling data to be output to the modeling unit 102. The modeling data includes information indicating the position of each voxel and information on the color of the selected ink.

  In step S <b> 26, ink ejection processing is performed in the modeling unit 102. By the processing in this step, the modeling unit 102 functions as the ink ejection unit 168. The processing unit 30 ejects ink of the selected color for each voxel for each layer constituting the three-dimensional object obtained in step S24. Each layer is stacked by repeating the ink ejection process from the lowermost layer to the uppermost layer in order along the Z-axis direction. Thereby, the three-dimensional object based on the input three-dimensional data is modeled.

  In the three-dimensional modeling apparatus 100 according to the present embodiment, the second color component (CMY), the white color (W), and the transparent color (T) are obtained from the first color signal composed of the first color component (RGB). A second color signal is generated. At this time, the ratio of white (W) and transparent color (T) to the second color component (CMY) is a value corresponding to the magnitude of the first color signal. Furthermore, the ratio of white (W) and transparent color (T) is determined according to the base color signal (A). Based on the second color signal generated in this way, the color of the ink to be ejected to each voxel is selected according to the ratio of the second color signal, and is selected for each voxel in the modeling unit 102. Ink is ejected. Accordingly, it is possible to model a three-dimensional object having a surface color that appropriately reproduces the input three-dimensional data by using the modeling unit 102 that ejects only one color ink for one voxel.

  Further, as shown in FIG. 9, the gradation expression changes depending on the ratio of the voxel ejected with the white (W) ink and the voxel ejected with the transparent color (T). As shown in FIG. 9, when the ratio of the transparent color (T) ink is increased, the density of the halftone is increased. Thus, by adjusting the ratio of voxels in which white (W) and transparent color (T) are used among the voxels constituting the object, the glossiness (glossiness) of the color when viewed from the object surface. Is properly expressed.

FIG. 10 shows an example of a three-dimensional object for explaining the effect of using white (W) and transparent color (T). In this example, it is assumed that four layers of voxels from the surface of the three-dimensional object are colored layers, and the fifth layer is a base material layer. In addition, white (W) ink is ejected to the voxel of the base material layer, and any one of three types of inks of magenta (M), white (W), and transparent color (T) is used for the voxel of the colored layer. Shall be discharged. As described above, when three types of ink are used for four layers of voxels, the ink arrangement is 81 (= 3 ⁴ ). FIG. 10 is an excerpt of nine out of 81 ink arrangements.

  Here, in FIG. 10, the third layer ink from the surface is white (W) in the fourth row, and is different from the transparent color (T) in the seventh row. That is, since the third layer is white (W) in the fourth row, light is reflected by the third layer. On the other hand, in the seventh row, since the third layer is a transparent color (T), the light passes through the third layer, passes through the fourth magenta (M), and passes through the fifth white layer as the base material layer. Reflected by (W). Therefore, the fourth row and the seventh row have different reflectances on the object surface. The reflectance on the entire object surface is represented by the product of the reflectance on the object surface of each ink array and its occurrence probability. According to the present embodiment, it is equivalent to controlling the probability of occurrence of rows having different reflectances, so that the glossiness (glossiness) of the object surface is appropriately controlled.

  Further, the ratio k may be changed according to the distance from the object surface. For example, in Equation (3), the ratio k may be increased in proportion to the distance from the object surface. As a result, as shown in FIG. 11, the W signal increases in proportion to the distance from the object surface, and the T signal decreases. Further, for example, in the formula (3), the ratio k may be decreased in proportion to the distance from the object surface. Thereby, as shown in FIG. 12, the W signal decreases in proportion to the distance from the object surface, and the T signal increases.

  As a result, the discharge ratio of white (W) ink and transparent color (T) ink changes according to the distance from the object surface, but white (W) ink and transparent are seen in the entire colored portion of the object. The ejection ratio of the color (T) ink is kept constant. Thus, by changing the ratio k in accordance with the distance from the object surface, the number of factors (parameters) used when controlling the glossiness of the object surface and the density of the gradation increases.

  The ratio k is not limited to a method of changing in proportion to the distance from the object surface, and the ratio k may be changed as a function using the distance from the object surface as an argument. For example, the ratio k may be changed in proportion to the square of the distance from the object surface, or may be changed exponentially with respect to the distance from the object surface.

<Second Embodiment>
As a second embodiment, the second color signal generation means 158 may obtain an A ′ signal obtained by correcting the A signal from the CMY signal. For example, the A ′ signal is calculated based on Equation (4). Here, the A signal is a value calculated by Equation (1), and is a real number between 0 and 1. A is a constant.
(Equation 4)
A '= (A + a) / (1 + a) (4)

Further, the second color signal correction means 160 corrects the corrected CMY data (C signal, M signal, Y signal) of the second color component in accordance with the A ′ signal based on the equation (5). C ′ signal, M ′ signal, Y ′ signal).
(Equation 5)
C '= (1-A') x C / (C + M + Y)
M '= (1-A') x M / (C + M + Y)
Y '= (1-A') x Y / (C + M + Y) (5)

Further, the transparent signal generating means 162 generates a W signal and a T signal in accordance with the A ′ signal based on Expression (6).
(Equation 6)
W = a / (1 + a)
T = A'-W (6)

  Hereinafter, similarly to the above embodiment, based on the C ′ signal, the M ′ signal, the Y ′ signal, the W signal, and the T signal generated by the ink color selection unit 164, the slice processing unit 166, and the ink ejection unit 168. Ink is ejected.

  FIG. 13 shows ink ejection ratios based on the C ′ signal, M ′ signal, Y ′ signal, W signal, and T signal generated in this embodiment. In FIG. 13, the vertical axis indicates the magnitude of the A ′ signal after correction, and the horizontal axis indicates the magnitude of the A signal before correction.

  In the three-dimensional modeling apparatus 100 according to the second embodiment, the glossiness (glossiness) of the object surface is easily controlled by changing the value of the constant a.

Note that the W signal and the T signal may be calculated using Equation (7) based on the base color signal (A signal) in the first embodiment.
(Equation 7)
W = a
T = AW (provided that A> = a)
= 0 (provided that A <a is satisfied) (7)

  FIG. 14 shows ink ejection ratios based on the C ′ signal, M ′ signal, Y ′ signal, W signal, and T signal when Expression (7) is used. In FIG. 14, the vertical axis indicates the magnitude of the corrected A ′ signal, and the horizontal axis indicates the magnitude of the A signal before correction.

  Also in this case, the glossiness (glossiness) of the object surface can be easily controlled by changing the value of the constant a.

  10 modeling stand, 12 stage, 14 ink tank, 16 ink head, 16A nozzle group, 16C, 16M, 16Y, 16W, 16T ink nozzle, 16V ultraviolet irradiation means, 18 head drive unit, 18a rail, 30 processing unit, 32 storage Unit, 34 input unit, 36 output unit, 38 communication unit, 100 3D modeling apparatus, 102 modeling unit, 104 control unit, 150 3D data acquisition unit, 152 voxelization processing unit, 154 color information allocation unit, 156 color space Conversion means, 158 second color signal generation means, 160 second color signal correction means, 162 transparent signal generation means, 164 ink color selection means, 166 slice processing means, 168 ink ejection means, 200 three-dimensional object.

Claims (8)

From the first color signal representing the first color component, the second color component signal representing the second color component constituting the output color and the base color component constituting the internal region other than the surface region of the three-dimensional object are represented. Second color signal generation means for generating a second color signal including a base color signal;
Transparent signal generating means for generating a white signal representing white and a transparent signal representing transparency at a hybrid ratio according to the magnitude of the base color signal;
A color signal processing apparatus comprising: The first color signal is set for each pixel,
The color signal processing apparatus according to claim 1, wherein the transparent signal generation unit sets a mixing ratio of the white signal and the transparent signal according to a distance of a pixel from an object surface.   The color signal processing apparatus according to claim 2, wherein the transparent signal generation unit decreases a ratio of the mixture of the transparent signal with respect to the white signal in accordance with a distance of a pixel from the object surface.   The color signal processing apparatus according to claim 2, wherein the transparent signal generation unit increases a ratio of the mixture of the transparent signal with respect to the white color signal according to a distance of a pixel from the object surface.   3. The transparent signal generation unit, wherein the white color signal is constant regardless of a distance of a pixel from the object surface, and the transparent signal is increased according to a distance of the pixel from the object surface. The color signal processing device according to 1.   6. An ink color selection unit that selects an ink color to be ejected in accordance with a ratio of the white color signal and the transparent signal constituting the second color component signal and the base color signal. The color signal processing apparatus according to any one of the above. Including the color signal processing device according to claim 1,
A three-dimensional modeling apparatus, comprising: an ink ejection unit that ejects ink of a color selected by the ink color selection unit. Computer
A first color signal representing a first color component, a second color component signal representing a second color component constituting an output color, and a base color signal corresponding to the magnitude of the first color signal; Second color signal generation means for generating a two-color signal;
Transparent signal generating means for generating a white signal representing white and a transparent signal representing transparency at a hybrid ratio according to the magnitude of the base color signal;
A color signal processing program characterized by being made to function.

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