JP2014224718A - Image processing apparatus and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To faithfully reproduce texture of an object.SOLUTION: An image processing apparatus includes: an input part for inputting gloss characteristic data indicating gloss characteristics of an object; a setting part which sets a focus position on the basis of the gloss characteristic data inputted by the input part and a reference gloss value; and an acquisition part which acquires deflection characteristic data of the object measured with a plurality of angles and focus positions, on the basis of the focus position.

Description

  The present invention relates to a texture reproduction technique for an object.

  In recent years, in the design stage of products such as cameras, computer graphics (hereinafter referred to as CG) is used to check a design on a monitor instead of creating a mockup. In order to confirm the finished product, it is required to reproduce the texture such as glossiness faithfully in the CG.

  As a reproduction method that is faithful to the texture of the real object, BRDF that represents the change in the angle of the object accompanying the change in the angle of the incident light / outgoing light and the BTF that is the BRDF distribution for each position of the object are actually measured, and the measured value is obtained. There is a method to reproduce the texture of an object. BRDF is an abbreviation of Bidirectional Texture Distribution Function, and BTF is an abbreviation of Bidirectional Texture Function.

  Depending on the gloss characteristics of the object, the sharpness of the image in which the surroundings are reflected in the object changes. Further, when the sharpness of the reflection is high, a human observes the reflected image, whereas when the sharpness of the reflection is low, the person tends to observe the object surface.

  On the other hand, the variable angle characteristic of an object differs depending on the focus position, which is the distance from the measuring instrument to the focus surface. For this reason, even if the measured value of the variable angle characteristic of an object is simply used for CG, it may not match the texture that humans feel. Therefore, in Patent Document 1, an exaggerated parameter is set, and the set exaggerated parameter is multiplied by a measured value of the angle change characteristic to reproduce the texture when a human observes the object.

JP 2008-243046 A

However, in the method of Patent Document 1, since the characteristics at the time of human observation are not associated with measurement, it is necessary to set exaggeration parameters in advance. In addition, since the angle change characteristic data is generated by simple multiplication, the generated angle change characteristic data does not necessarily reflect the actual characteristic, and the texture may not be faithfully reproduced.
Therefore, an object of the present invention is to faithfully reproduce the texture of an object.

  An image processing apparatus according to the present invention includes an input unit that inputs gloss characteristic data indicating the gloss characteristics of an object, and a setting unit that sets a focus position based on the gloss characteristic data and the reference gloss value input by the input unit. And an acquisition unit that acquires the variable angle characteristic data of the object measured at a plurality of angles and a plurality of focus positions based on the focus position.

  The present invention can faithfully reproduce the texture of an object.

1 is a block diagram illustrating a configuration of an image processing apparatus according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating the principle of processing performed by the image processing apparatus of the image processing apparatus according to the first embodiment. 3 is a flowchart illustrating processing in the image processing apparatus according to the first exemplary embodiment. The conceptual diagram which shows the acquisition method of a variable angle characteristic. The figure which shows an example of the variable angle characteristic data. 7 is a flowchart of focus position setting processing in Embodiment 1. The figure which shows the difference in the variable angle characteristic of an object with a high gloss characteristic, and an object with a low gloss characteristic. FIG. 4 is a block diagram illustrating a configuration of an image processing apparatus according to a second embodiment. 9 is a flowchart showing processing of an image processing apparatus in Embodiment 2. 9 is a flowchart of a variable angle characteristic acquisition process in the second embodiment. 10 is a flowchart of light amount calculation processing in the second embodiment. The figure which showed an example of the geometric conditions for implementing rendering. 10 is a flowchart of a variable angle characteristic acquisition process according to the third embodiment.

  Hereinafter, image processing according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition, about the same structure, the same code | symbol is attached | subjected and demonstrated.

  The configuration of the image processing apparatus according to the present embodiment will be described with reference to the block diagram of FIG. The material characteristic input unit 11 inputs gloss characteristic data of a target object (hereinafter also referred to as an object) whose texture is to be reproduced. The focus position setting unit 12 sets a focus position that is a distance from the measuring instrument to the focus surface when measuring the variable angle characteristic of the object based on the gloss characteristic data input by the material characteristic input unit 11. The variable angle characteristic measuring unit 13 measures the variable angle characteristic of the object based on the focus position set by the focus position setting unit 12. The variable angle characteristic output unit 14 outputs the measurement data measured by the variable angle characteristic measuring unit 13 to the variable angle characteristic holding unit 15. The variable angle characteristic holding unit 15 holds the measurement data output from the variable angle characteristic output unit 14. The image processing apparatus includes a central processing unit (CPU) (not shown) that controls the entire apparatus, and includes a read-only storage device (ROM) and a storage device (RAM) that the CPU temporarily reads and writes during calculation processing.

<Processing Performed by Information Processing Device in Embodiment 1>
The principle of processing executed by the image processing apparatus in this embodiment will be described. When a human observes an object with high gloss characteristics (for example, a mirror), he / she pays attention to an image reflected on the object. Therefore, for example, when an object is observed indoors, illumination reflected in the object is observed. On the other hand, when observing an object with low gloss characteristics (for example, a solid coated plate having a matte surface), attention is paid to the texture of the object surface. Therefore, for example, when an object is observed indoors, fine textures and scratches on the surface of the object are observed.

  FIG. 2 shows an angle change characteristic when the same object is irradiated with parallel light from a direction with an elevation angle of 45 degrees and when the focus position is set on the sample surface and when the focus position is set on the reflected illumination image. The measured data is shown.

  FIG. 2A is a diagram showing the relative relationship between the reflection intensities of the two deflection characteristics. In FIG. 2A, a solid line 201 is a measured value of the variable angle characteristic with the focus position set on the sample surface (hereinafter also referred to as sample surface focus), and a wavy line 202 sets the focus position on the illumination image (hereinafter referred to as “focus position”). This is a measured value of the variable angle characteristic (also called illumination image focus). The solid line 201 and the wavy line 202 are normalized so that the maximum value of the reflection intensity of the wavy line 202 is 1. As shown in FIG. 2A, the sample surface focus measurement data has a reflection intensity range of 100: 1, whereas the illumination image focus reflection intensity has a range of 300: 1 and two measurement data. The range is very different.

  FIG. 2B is a diagram comparing the relative relationship between the shapes of the two deflection characteristics. The solid line 203 is the declination characteristic data set with the focus position set on the sample surface, and the wavy line 204 is the declination characteristic data set with the focus position on the illumination image, normalized so that each reflection intensity becomes 1. FIG. As shown in FIG. 2B, it can be seen that the difference between the half-value widths (angles when the reflection intensity is halved from regular reflection) of both data is different from about 0.3 degrees.

  Therefore, in order to faithfully reproduce the texture of the object, it is important to use the variable angle characteristic measured at an appropriate focus position in accordance with the gloss characteristic of the object. The image processing apparatus in the present embodiment uses a variable angle characteristic in which the focus position at the time of observation is appropriate according to the gloss characteristic of the object.

  Hereinafter, processing executed by the image processing apparatus according to the first embodiment will be described with reference to the flowchart of FIG.

  In step S301, the gloss characteristic data of the target object instructed by the user from the material characteristic input unit 11 is input. In this embodiment, as the gloss characteristic data of the target object, the object is measured in advance at a predetermined multiple angles and focus positions, and selected from a plurality of variable angle characteristic data held in a memory (not shown) according to a user instruction. It is assumed that the input is input.

  In step S <b> 302, the focus position setting unit 12 sets the focus position D based on the gloss characteristic data input by the material characteristic input unit 11. Details of the processing in step S302 will be described later.

  In step S <b> 303, the variable angle characteristic measuring unit 13 measures the variable angle characteristic of the object based on the focus position D set by the focus position setting unit 12. FIG. 4 is a diagram showing the concept of the variable angle characteristic measuring method executed by the variable angle characteristic measuring unit 13. In FIG. 4, a light source 401 is a parallel light source for irradiating a target object 403. For example, in addition to a white halogen lamp, laser light or the like can be used. The light receiver 402 can change the angle around the center position of the target object 403. The light receiver 402 acquires the amount of reflected light emitted from the light source 401 and reflected by the target object 403. Here, the light receiver 402 will be described as an imaging device, but the imaging device is not necessarily an imaging device, and may have any light receiving element on a plane. An image 404 is an illumination image reflected on the sample.

As the image 404 indicates, the illumination image reflected on the target object 403 can be regarded as being in a symmetric position with respect to the target object plane. Therefore, the light receiver 402 with respect to the light source 401, for example, if installed in the specular direction, the image 404 can be regarded as a distance D _L away when directly facing the light receiver 402.

  A position 405 is a position set by the focus position setting unit 12. That is, as shown in FIG. 4, the light receiver 402 performs imaging so as to focus on a position 405 separated from the light receiver by D in the direction of the sample surface.

In the configuration as described above, the variable angle characteristic measurement unit 13 performs imaging while changing the incident angle (θ _in , φ _in ) and the light receiving angle (θ _out , φ _out ) with respect to the object. In the above description, the deflection characteristic of the object is acquired by photographing. On the other hand, a plurality of variable angle characteristic data indicating the variable angle characteristics of the object measured in advance by a plurality of angles and a plurality of focus positions are held in a memory (not shown), and the focus position D set in step S302 is stored therein. Deflection characteristic data corresponding to may be acquired.

In step S304, the variable angle characteristic output unit 14 collects the pixel values of the common pixel positions for each image of the captured data captured by the variable angle characteristic measurement unit 13 in step S303 for each captured image. The converted angle characteristic data is output to the variable angle characteristic holding unit 15. FIG. 5 is a diagram showing an example of the angle change characteristic data held by the angle change characteristic holding unit 15. As shown in FIG. 5, in addition to information on the focus position at the time of measurement, reflectance data for each incident angle (θ _in , φ _in ) and each receiving angle (θ _out , φ _out ) for each position (x, y). Is stored.

<Details of Step S302>
Hereinafter, the focus position setting method in step S302 will be described with reference to the flowchart of FIG.

  In step S601, an angle θ satisfying Equation 1 is calculated from the gloss characteristic data input in step S301.

  In Expression (1), Imax is the maximum value of the reflection intensity, and θ corresponds to a half-value width that is an angle at which the reflection intensity becomes half value.

  FIG. 7 is a diagram showing the deflection characteristics of two materials having different gloss characteristics. A solid line 701 represents the angle change characteristic of an object having high gloss characteristics, and a wavy line 702 represents the angle change characteristic of an object having low gloss characteristics. As shown in FIG. 7, the full width at half maximum of an object with high gloss characteristics is as low as about 0.5 degrees, while the full width at half maximum of an object with low gloss characteristics is as high as about 5.0 degrees. Therefore, in this step, the half-value width θ of the variable angle characteristic is used as the gloss value indicating the gloss characteristic of the object.

In step S602, using the ratio between the half-value width θ calculated in step S601 and the gloss value (reference gloss value) of the reference high-gloss sample and low-gloss sample, the focus is calculated by the following equation (2). The position D is calculated. In Equation (2), θ _H is the half-value width of the variable angle characteristic of the reference high-gloss sample, for example, the half-value width of black polished glass (BK7). θ _L is the half-value width of the variable angle characteristic of the low-gloss sample as a reference, for example, the half-value width of a solid coated plate in which pigment particles (metal oxide or the like) are dispersed in enamel (binder). θ _H and θ _L are stored in advance in a memory (not shown). As shown in FIG. 4, _DH is the distance from the light receiver 402 to the target object 403, and _DL is the distance from the light receiver to the light source when facing the light receiver (that is, the light receiver 402). And the distance of the illumination image 404).

  According to the present embodiment, it is possible to acquire variable angle characteristic data appropriate for the gloss characteristic of an object in consideration of human characteristics during object observation.

  In the first embodiment, the method for measuring the angle change characteristic according to the gloss characteristic of the object has been described. In the present embodiment, a method for reproducing the texture of an object using measured deflection angle characteristic data will be briefly described focusing on differences from the first embodiment.

  The configuration of the image processing apparatus according to the second embodiment will be described with reference to the block diagram of FIG. In FIG. 8, the variable angle characteristic holding unit 81 holds variable angle characteristic data obtained by measuring the variable angle characteristic of an object at a plurality of focus positions. The material characteristic input unit 82 inputs gloss characteristic data of an object that is a target for reproducing a texture. The variable angle characteristic acquisition unit 83 acquires the variable angle characteristic data of the object to be reproduced from the variable angle characteristic data of the variable angle characteristic holding unit 81 based on the material characteristic data input by the material characteristic input unit 82. The rendering unit 86 includes the variable angle characteristic data acquired by the variable angle characteristic acquisition unit 83, the ambient light information held in the environment information holding unit 84, and the tertiary of the object held in the 3D shape holding unit 85. A CG image is generated using the original shape data. The image output unit 87 outputs the CG image calculated by the rendering unit 86 to an external output device such as a display.

  Hereinafter, processing executed by the image processing apparatus according to the second embodiment will be described with reference to the flowchart of FIG.

  Since step S901 is the same as step S301 in the first embodiment, description thereof is omitted.

  In step S902, the variable angle characteristic acquisition unit 83 acquires variable angle characteristic data of the object based on the gloss characteristic data input in step S901. Details of step S902 will be described later.

  In step S903, the variable angle characteristic data of the object acquired in step S902, the ambient light information held in the environment information holding unit 84, and the three-dimensional shape data of the reproduced object held in the 3D shape holding unit 85 are obtained. Based on this, the amount of light reflected by the object is calculated to generate a CG image. Details of step S903 will be described later.

  In step S904, the image output unit 87 outputs the CG image calculated in step S902 to an external output device such as a display.

<Details of Step S902>
In the following, the variable angle characteristic acquisition method according to the second embodiment will be described with reference to the flowchart of FIG.

  Steps S1001 and S1002 are the same as steps S601 and S602 in the first embodiment.

  In step S1003, the variable angle characteristic data of the object measured at the focus position D calculated in step S1002 is acquired from the variable angle characteristic holding unit 81.

<Details of Step S903>
Hereinafter, the light amount calculation processing in step S903 in the second embodiment will be described with reference to the flowchart of FIG.

  In S1101, the illumination data stored in the environment information holding unit 84 is read.

  In S1102, the 3D shape data of the object stored in the 3D shape holding unit 85 is read.

  In step S1103, the virtual camera, virtual screen, object position, and illumination position geometric conditions for rendering are set. FIG. 12A is a diagram illustrating an example of a geometric condition for performing rendering.

  In step S1104, the target pixel on the virtual screen is set to an initial value (for example, a pixel with X = 0, Y = 0).

  In S1105, a straight line connecting the virtual camera and the target pixel on the virtual screen is set as a line-of-sight vector, and an intersection (xc, yc, zc) between the line-of-sight vector and the target object is calculated.

  In S1106, the normal vector N of the target object at the intersection calculated in S1105 is calculated.

  In S1107, an illumination vector N that connects the intersection calculated in S1105 and the illumination is calculated.

  In S1108, the angle-changing characteristic data of the target object at the intersection calculated in S1105 is set. Specifically, BTF (x, y, φ), which is the deflection characteristic of the position (x, y) corresponding to the intersection calculated in step S1105, is set.

  In S1109, the luminance value of the target pixel is calculated using the variable angle characteristic data calculated in S1108, the line-of-sight vector, the normal vector, and the illumination vector.

  In S1110, it is determined whether or not the luminance calculation processing has been performed for all the pixels on the virtual screen. If completed, the process proceeds to S1112. If not completed, the process proceeds to S1111.

  In step S1111, the target pixel is changed to an unprocessed pixel on the virtual screen, and the process returns to step S1105.

  In S1112, a CG image is drawn based on the luminance data calculated in S1109.

  FIG. 12B shows the relationship between the line-of-sight vector, the normal vector, and the illumination vector in steps S1105 to S1108.

  According to the present embodiment, it is possible to faithfully reproduce the texture at the time of object observation by using the variable angle characteristic data suitable for the gloss characteristic of the object.

  In the second embodiment, the explanation is made on the assumption that the measured value of the changing angle characteristic of the focus position is measured in advance in the changing angle characteristic acquisition unit. However, measurement data measured at a desired focus position is not always held in the variable angle characteristic holding unit. Therefore, in this embodiment, the variable angle characteristic acquisition unit estimates the variable angle characteristic of an arbitrary focus position even when the measured value of the desired focus position is not held. A case where the texture is faithfully reproduced using the estimated angle-change characteristic data will be briefly described focusing on differences from the first and second embodiments.

<Details of Process Regarding Deflection Characteristic Acquisition Method in Example 3>
Hereinafter, the variable angle characteristic acquisition process in the third embodiment will be described with reference to the flowchart of FIG.

  Step S1301 and step S1302 are the same as step S1001 and step S1002.

In step S1303, focus positions _DN and _{DN +} 1 satisfying the following expression (3) are acquired. In Expression (3), _DN is a value smaller than D and closest to D, and _{DN + 1} is a focus position larger than D and closest to D. However, _DN and _{DN + 1} are focus positions used for measurement.

In step S1104, the variable angle characteristic data corresponding to _DN and _{DN + 1} acquired in step S1103 is acquired from the variable angle characteristic holding unit, and the variable angle characteristic data corresponding to the focus position D is obtained by the following equation (4). Generate.

In Expression (4), BTF _N and BTF _{N + 1} are the angle change characteristic data of the focus position D and the angle change characteristic data of the focus position D _{N + 1} , respectively.

  According to this embodiment, even if the angle change characteristic at a desired focus position is not measured in advance, the texture of the object can be reproduced by estimating the angle change characteristic data at an arbitrary focus position. It becomes.

[Other Examples]
In the third embodiment, the method of estimating the variable angle characteristic data when the desired measurement value is not measured has been described. However, the estimation is not necessarily required. For example, the change angle characteristic data of the focus position closest to the focus position D may be selected from the change angle characteristic holding unit.

  In the above embodiment, the angle difference characteristic data simply measured as the material characteristic of the object is input and the half-value width is calculated. However, the present invention is not limited to this as long as the data corresponds to the gloss characteristic. For example, the calculated data may be the maximum value of the reflection intensity of the variable angle characteristic of the object instead of the half width. In this case, if the object has high gloss characteristics, the value is large, and if the object has low gloss characteristics, the value is small. Therefore, the maximum value can be used.

  The input data may be data on the surface roughness of the object. In this case, the dispersion value of the surface roughness can be calculated, and the higher the dispersion value, the lower the gloss, and the smaller the dispersion value, the higher the gloss. Therefore, the roughness data can be used.

  The present invention can also be realized by supplying a storage medium storing a program code of software for realizing the functions of the above-described embodiments (for example, the steps shown in the above flowchart) to a system or apparatus. In this case, the functions of the above-described embodiments are realized by the computer (or CPU or MPU) of the system or apparatus reading and executing the program code stored in the storage medium so that the computer can read the program code. Further, the program may be executed by one computer or may be executed in conjunction with a plurality of computers.

Claims (8)

An input unit for inputting gloss characteristic data indicating the gloss characteristic of the object;
A setting unit for setting a focus position based on the gloss characteristic data and the reference gloss value input by the input unit;
An image processing apparatus comprising: an acquisition unit configured to acquire change angle characteristic data of an object measured at a plurality of angles and a plurality of focus positions based on the focus position.   The acquisition unit measures an angle change characteristic of an object measured at a plurality of angles and a plurality of focus positions based on the focus position, and the focus position is a distance between a light receiver and a focus surface at the time of the measurement. The image processing apparatus according to claim 1, wherein the image processing apparatus is provided.   3. The image processing apparatus according to claim 1, wherein the gloss characteristic includes at least one of a reflection intensity, a half-value width, and a surface roughness dispersion value of the variable angle characteristic data. .   The focus position set by the setting unit is the distance between the light receiver and the sample surface, the distance when the light receiver and the light source are directly opposed, the reflection intensity calculated from the material characteristics of the object, the half width, The image processing apparatus according to claim 1, wherein the image processing apparatus is calculated from a ratio of any one of the dispersion values of the surface roughness. A generation unit that generates a CG image using the deflection characteristics for each pixel of the object;
The image processing apparatus according to claim 1, wherein the generation unit generates the CG image from the variable angle characteristic data acquired by the acquisition unit.   The said acquisition part estimates the angle-change characteristic of arbitrary focus positions using the angle-change characteristic data acquired in these focus positions, The Claim 1 thru | or 5 characterized by the above-mentioned. Image processing apparatus.   A program that causes a computer to function as each unit of the image processing apparatus according to any one of claims 1 to 6. An input step in which the input unit inputs gloss characteristic data indicating the gloss characteristics of the object;
A setting step in which the setting unit sets a focus position based on the gloss characteristic data and the reference gloss value input by the input unit;
An image processing method comprising: an acquisition unit that acquires, based on the focus position, variable angle characteristic data of an object measured at a plurality of angles and a plurality of focus positions.

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