JP2524099B2 - 3D graphic display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional graphic display device provided with shading, and more particularly to a display device having a brightness control device suitable for shading display of an object based on a light reflection model.

[0002]

2. Description of the Related Art In order to display a three-dimensional figure on a two-dimensional device with a natural stereoscopic effect, it is well known that the brightness of each point of the figure to be displayed is changed depending on the location (shading). One of the model formulas for calculating the brightness is introduced in the following document.

"Fundamentals of Interactive Computer Graphics", Addison Wesley Publish Company ("Fundamen
tals of Interactive Computer Graphics ”, Addison W
esely Publishing Company), 1982, pp 575-5
78.

That is, the intensity (luminance) of reflected light arriving at a viewpoint from a point (reflection point) on a certain image (reflection surface).
Is represented by equation (1).

[0005]

[Equation 1]

FIG. 2 illustrates various vectors appearing in equation (1). Here, among the various variables, K _a, the value of K _d, K _s, k, other than n variables will vary depending on the position of each reflection point on the reflecting surface. K _a , K _d ,
K _s , n differs depending on the material forming the reflection surface, and does not depend on the position of each reflection point on the reflection surface.
Further, K _a , K _d , K _s , I _a , and I _p are divided into a red component (R), a green component (G), and a blue component (B), and equation (1) is established for each color component. I do. This is the same for the following equation.

[0007]

[Equation 2]

By the way, the inner product (→ R · → V) of the third term in the above equation (1) is calculated in the intermediate direction between the light source and the line of sight (→ L and → V
Unit vector of the direction of the sum of
→ H), and the equation (1) is transformed into the following equation (3).

[0009]

(Equation 3)

Formula (3) can be considered as the sum of the following two terms.

[0011]

[Equation 4]

[0012]

(Equation 5)

[0013] formula (4) is I _a K _a is the diffusion reflection light component caused by the ambient light, the remainder being diffuse reflected light component by the light from the light source. Therefore, I _ad ′ represents the diffuse reflection light component as a whole. On the other hand, the I _s ′ specular reflected light component of the equation (5) is shown. Moreover, these two components are both functions of the depth value (distance between the viewpoint and the reflection point) r and the unit normal vector → N of the reflection surface.

In the technique described in the above-mentioned publication pp543, 544, the brightness I of each point is changed and displayed only by the depth value r.

Further, in the figure shading device of Japanese Patent Application No. 59-223922 filed prior to the present application and published after the priority date of the present application, the depth value r in the equation (3) is regarded as constant, and The brightness I of each reflection point is calculated by the equation (6).
It was proposed to calculate and display.

[0016]

(Equation 6)

Where C: constant

[0018]

In a display device for displaying a three-dimensional figure two-dimensionally, a luminance I of a point (reflection point) on the three-dimensional figure corresponding to the display pixel is calculated for each display pixel. There is a need to. However, if the above equation (3) is used for the calculation, the calculation takes a very long time because the equation (3) includes multiplication and division.

Further, in the display technique in which the brightness is changed only by the depth value r, different surfaces having the same depth value r have the same brightness, and the three-dimensional value is not sufficient depending on the displayed figure.

Further, as in the display device of the above-mentioned formula (6) in which the depth value r is assumed to be constant, when the luminance changes only in the direction of the reflecting surface, when the pictures of a plurality of figures to be displayed exist in the same direction, However, when they are at the same angle as the direction of the light source / viewpoint, those figures are displayed with the same brightness, so if those figures are adjacent, the boundaries of those figures cannot be identified, The three-dimensional effect may be lost.

The depth value r depends on the use of the display device.
There is a case where it is desired to increase the luminance change due to the difference between the two, and a case where it is desired to increase the luminance change due to the difference of the direction of the reflection surface → N.
However, such a technique cannot be performed by the conventional technique.

An object of the present invention is to determine the luminance I of a point (reflection point) on a three-dimensional figure displayed at each display pixel position by using the normal direction of the reflection surface at the reflection point (hereinafter simply referred to as the direction of the display pixel). And a depth value of the reflection point (hereinafter simply referred to as a depth value of the display pixel), and a display device capable of determining the luminance I at a high speed. It is in.

Still another object of the present invention is to provide a depth value r
It is an object of the present invention to provide a device capable of appropriately changing the ratio of the luminance change due to the display pixel direction and the luminance change due to the display pixel direction → N.

[0024]

In the present invention, the equation (3) is modified as follows.

[0025]

I = I _r + I _N (7) where

[0026]

(Equation 8)

[0027]

[Equation 9]

[0028] Equation (8), equation (3) two inner product of a portion other than I _a K _a of (→ N · → L), respectively constants C ₁ and the value of (→ N · → H), C 2 This is an approximation. Where K
₁ , K _a , and K _s are quantities determined in advance by the material of the reflection surface of the figure to be displayed. Therefore, for a plurality of display pixels in the same plane, I
_r changes.

On the other hand, equation (9) is the depth value r of equation (3).
Is regarded as a constant value C ₄ . here,
K _d and K _a are predetermined amounts depending on the material of the reflection surface of the graphic to be displayed. Therefore, equation (9) shows that if the material of the picture of a figure is determined, two inner products (→ N · → L),
Depends on (→ N ・ → H).

By the way, in equations (8) and (9), K
_1, K ₂ is a numerical value for determining the I _r, the relative proportions of I _N. When the luminance I is calculated by Expression (7), which is the addition of Expression (8) and Expression (9), the value is different from the value calculated by Expression (3). However, in an actual graphic display device,
The precise value of the luminance I does not matter, but rather the luminance I is determined by the depth value r with respect to the display pixel, the pixel direction → N,
It depends on the material of the image. Therefore, even if a graphic is displayed with the luminance obtained by equation (7), the distribution of the luminance is not unnatural at all.

Further, since I _r and I _N depend only on one of r and → N, their calculations are easy. further,
By appropriately determining the ratio of K ₁ and K ₂ in Expressions (8) and (9), it is possible to arbitrarily change the ratio of the luminance change depending on the depth value and the luminance change depending on the pixel direction. This is useful for some display purposes.

According to the three-dimensional graphic display device of the present invention, a display means and a plurality of pixels constituting a display screen of the display means are provided.
For each display pixel included in the two-dimensional figure obtained by projecting the three-dimensional figure to be displayed on the two-dimensional plane, the display positions X and Y of each display pixel and the depth on the three-dimensional figure corresponding to the display position Pixel generating means for outputting a value and a luminance code determined depending on the normal direction of each surface of the three-dimensional figure;
A depth buffer which stores and holds the depth value output from the pixel generating means in correspondence with each display position, and a luminance code which depends on the direction output from the pixel generating means in correspondence with each display position A frame buffer to be held, a depth value from the depth buffer, and a luminance code from the frame buffer are inputted as reference addresses, and a color lookup table for converting into color information of each display position, and a color lookup table of the color lookup table. And a DA converter that converts the output into an analog luminance signal, and displays on the display means according to the luminance signal output by the DA converter.

[0033]

In the apparatus of the present invention, the first means outputs the depth value of each pixel of the display figure, the normal direction of the pixel, and the display position on the screen, and the second means outputs the first value. The means outputs the luminance corresponding to the depth value, the third means outputs the luminance corresponding to the normal direction of the pixel, which is the output of the first means, and the fourth means outputs the luminance. The signals to be sent to the display means having the display pixels are synthesized from the luminance signals output from the second and third means. The second and third luminance output means are obtained by referring to a table set in advance,
In the fourth means, the luminance that changes depending on the depth value and the luminance that changes depending on the pixel direction are combined to obtain the sum of the luminance signals of the two or the gain of the luminance signal that changes depending on the direction of the pixel corresponding to the depth value. By adjusting, brightness control can be performed at high speed.

[0034]

FIG. 1 shows the overall arrangement of a first embodiment of the present invention.

The coordinate conversion processor 20 receives display data and viewpoint position data relating to each of a plurality of figures to be displayed simultaneously from the host processor 10 and performs visual conversion for display and conversion for enlargement / reduction. And so on. Here, the display data includes three-dimensional polyline (line segment sequence) data or three-dimensional polygon (picture figure) data having coordinate values at each vertex of each figure and a unit normal vector, and a material number of each figure. Here, the coordinate values are the X and Y coordinate values projected on the screen by visual conversion in the coordinate conversion processor 20, and the Z coordinate values are perpendicular to the screen which is the projection surface of the three-dimensional figure from the viewpoint. It is the distance to the figure measured in the direction. In general, if the distance between the figure and the viewpoint is sufficiently longer than the distance between the figure and the projection plane (screen), the Z coordinate and the depth value r of the model equation can be approximated to the same value.

The pixel generation processor 30 sequentially performs the following processing for each figure. That is, the material number M of the figure being processed is set in the register 43. Next, the positions of a plurality of display pixels required to display the figure are determined from the display data after the coordinate conversion. The position of each display pixel (X,
Y, Z) are obtained by interpolation from the values of the vertices of each figure. As described above, the Z coordinate is used as the depth value r.

The depth buffer 74 has, for each display pixel on the display screen, an area for storing a depth value of a point on the figure displayed thereon.

Similarly, the frame buffers 71 to 73 are
For each display pixel on the display screen, the red component I _R , the green component I _G , and the blue component I _B of the luminance I of the point on the figure displayed there are
Has an area for storing each.

The pixel generation processor 30 calculates the X and Y coordinates of the display pixel as the address of the corresponding storage area in the depth value buffer 74 and the frame buffers 71 to 73 for the one determined display pixel. Output to buffer. Here, each storage area of the buffers 71 to 74 is provided corresponding to a pixel on the display screen.
The coordinates (X, Y) on the display screen and the address (X, Y) of the storage area have a one-to-one correspondence.

The depth buffer 74 sends the depth value r (Z coordinate) generated for the currently processed display pixel, and the internal calculation circuit 41 outputs the unit normal vector of the reflecting surface → N, the light source direction. The unit vector Σ is transmitted, the unit normal vector → N of the reflecting surface, the light source / line of sight intermediate direction unit vector → H are transmitted to the inner product calculating circuit 42, and the depth buffer 7
4. The address and write enable signal WE for the display pixel being processed are selected for the frame buffers 71 to 73. The depth value r generated in the depth buffer 74
Is written into the frame buffers 71 to 73, and the R, G, and B components I _{R of} the brightness I calculated as follows are calculated.
I _G and I _M are written.

The inner product calculation circuits 41 and 42 output the normal vector of the display pixel → N and the unit vector of the light source direction → L, and → N and the unit vector of the light source / gaze intermediate direction → H output from the pixel generation processor 30, respectively. , And calculate the inner products (→ N · → L) and (→ N · → H), respectively. The outputs of the processors 41 and 42 are combined with the material number M in the register 43 and used as a read address for the luminance tables 51 to 56.

The luminance tables 57 to 59 have depth values r.
And the luminance component, which depends on the surface material of the figure,
It is stored in advance for each of the G and B components. That is, the R, G, and B components I _ra , I _rG , and I _rB of the brightness I _r determined by the equation (8) are calculated by changing the depth value r for a certain material in advance. This calculation is performed by changing the material.
The data obtained in this way is sequentially stored in the storage positions determined depending on the material number and the depth value r in the tables 57 to 59 for each of the R, G, and B components. Therefore, the material number M in the register 43 and the pixel generation processor 3
When the depth values r output from 0 are combined and these luminance tables 57 to 59 are accessed as read addresses, the luminance components I _rR , I _rG , and I are respectively accessed.
_rN is output to the adders 64-66, respectively.

On the other hand, the luminance tables 51 to 56 previously store luminance components which are determined depending on the direction of the display pixel → N and the material of the reflection surface. That is, equation (9) can be further considered as the sum of two quantities.

[0044]

(10) I _M = I _ad + I _s (10)

[0045]

[Equation 11]

[0046]

(Equation 12)

The luminance I _{ad in the} equation (11) includes a reflected light component due to ambient light and a diffuse reflected light component. Luminance I _s of formula (12) is composed of only the specular reflection light component. in advance,
R, G, and B components I _{adR of} the luminance I _ad determined by Expression (11),
I _adG and I _adB are calculated by changing the value of the inner product value (→ N · → L) for a material with a graphic image, and the same calculation is performed by changing the material. The results obtained in this way are expressed by the material numbers and inner product values (→ N · → L) in the luminance tables 51 to 53, respectively.
Is stored in a storage location determined depending on

Meanwhile, R in intensity I _s determined by equation (12), G, likewise the material and the inner product value also B component (→
N.fwdarw.H) and store the calculated value in advance.

Therefore, when the output (→ N · → L) from the inner product calculation circuit 41 and the material number M in the register 43 are combined and supplied to the tables 51 to 52, the corresponding table is obtained from these tables. Luminance I _adR , I _adG , I _adB
Are output to adders 64-66, respectively.

Similarly, the output of the inner product calculating circuit 42 (→ N ·
→ H) and the material number M in the resist 43 are combined and supplied to the tables 54 to 56 as addresses, from these tables, the corresponding luminances I _sR , I _sG , and I _sB are added to the adders ₆₄ to ₅₆ , respectively. It is output to 66.

Thus, the adders 64-66 add the luminances I _r , I _r added by the equations (8), (11) and (12).
_ad, performs addition for R, G, B components of I _s, R a final luminance I, G, B component I _R, I _G, selects respectively the I _B in the frame buffer 71 to 73. These buffers are address output from the pixel generator processor 30 (X, Y) and in response to the write enable signal WE, and stores the output I _R of the adder 64 to 66, I _G, the I _B, respectively.

Thus, the generation of the luminance data and the writing to the frame buffers 71 to 73 for one pixel are completed.

Hereinafter, the same processing is performed for other display pixels.

The contents of the frame buffers 71 to 73 are raster-scanned and converted into analog video signals by DA converters 84, 85 and 86, respectively, to control the brightness of the CRT display 90.

The above-mentioned writing of data in the depth buffer 74 and the frame buffers 71 to 73 is not performed for so-called drawing data. That is,
Pixel generating processor 30, before writing the depth r of the depth buffer 74, reads out the previously stored depth value r _s to the write position. This value _ro is a depth value for a certain point on another graphic. The pixel processor 30 compares the depth value r _o with the depth value r generated by the pixel generation processor 30, and when the former is smaller than the latter, the pixel generation processor 30 sends the write enable signal WE to the buffers 70 to 74. Not sent to. That is,
The above-described rewriting is not performed on the depth buffer 74 and the frame buffers 71 to 73. Thus, when data r _o read from the depth buffer 74 is smaller than the depth value r generated by the pixel generator processor 30,
This is the case where another graphic exists before the graphic to be displayed by the pixel generation processor 30. In this case, in order to not display the latter (so-called drawing erasure), for the display pixel currently being processed, Buffer 7
No changes are made to 4, 71 to 73.

As is clear from the above, in this embodiment, since the data necessary for calculating the luminance I is stored in the luminance tables 51 to 59, the calculation of the luminance can be performed at high speed. Further, the data in each luminance table includes a depth value r, an inner product (→
N, → L) or (→ N, → H) and only the material of the image, so that the depth value r and the inner product values (→ N, → L), (→ N, → H). Further, the data stored in these tables is obtained by changing the coefficients K ₁ and K ₂ shown in Expressions (8) and (9) to obtain the luminance I _r depending on the depth value r or the inner product (→ N · → L), can be easily changed relative ratio of the luminance I _N that depends on (→ N · → H).

FIG. 3 shows a second embodiment of the present invention.

The host processor 10, the coordinate conversion processor 20, the pixel generation processor 30, the inner product calculation circuits 41 and 42, the register 43, the depth buffer 74, the DA converters 84 to 86, and the CRT display 90 are the same as those in the embodiment of FIG. Is the same. In FIG. 3, a frame having a storage area corresponding to each of the display pixels of the CRT display 90 for newly storing the material number M and the inner product values (→ N · → L) and (→ N · → H), respectively. Buffers 75 to 77 are newly provided. As shown in FIG. 1, the inner product calculation circuits 41 and 42 provide, for each pixel for displaying a figure,
The inner product values (→ N · → L) and (→ N · → H) are calculated.
The outputs of these circuits and the material number M in the register 43
Is written to the frame buffers 75 to 77 according to the address (X, Y) output from the amphibian generation processor 30 and the write enable signal. These frame buffers 75 to 77 and depth buffer 74
It is read in synchronization with the address 200 from the display 90.

The color lookup table 83 is shown in FIG.
Luminance data I _rR held in brightness table 57, 58 and 59 of, I _rG, collectively I _rB, the depth r and the material number M
Are stored in advance in storage locations corresponding to the combinations of.

The color lookup table 81 is shown in FIG.
The brightness data I _adR , I _adG , and I _adB held in the brightness tables 51, 52, and 53 are collectively stored in advance in a storage position corresponding to the combination of the material number M and the inner product value (→ N · → L). ing.

The color look-up table 82 is shown in FIG.
The brightness data I _sR , I _sG , and I _sB held in the brightness tables 54, ₅₅ , and ₅₆ are collectively stored in a storage position corresponding to the combination of the material number M and the inner product value (→ N · → H). are doing. As described above, when the depth buffer 77 and the frame buffers 75 to 77 are accessed in synchronization with the scanning of the CRT display 90, the depth value r, the material number M, the inner product value (→ N.fwdarw.L) and (.fwdarw.N.fwdarw.H) are read from the buffer, and the read depth value r and the material number M are supplied as addresses to the color lookup table 83 and correspond to them. Luminance data I _rR ,
I _rG and I _rB are read to the adders 101, 102 and 103, respectively. Similarly, the read material number M and the inner product value (→ N · → L) are supplied to the color lookup table 81 as an address, from which the luminance data I _adG ,
I _adR and I _adB are read out and are added to the adders 101 and 1 respectively.
It is sent to 02, 103. Similarly, the read material number M and the inner product value (→ N · → H) are input to the color lookup table 82 as addresses, and the brightness data I _sR , I _sG , and I _sB are read out, respectively. Adder 10
1, 102 and 103. Adders 101, 1
02 and 103 add the input luminance data to obtain final luminance data I _R ,
I _G, and sends to the CRT display to generate I _B.

Thus, FIG. 3 can obtain substantially the same result as the circuit of FIG.

FIG. 4 shows another embodiment of the present invention. FIG.
, 10, 20, 30, 41, 74, 75, 84
86, 90 are the same as those in FIG. 4, the frame buffers 76 and 77, the color lookup table 82, and the adders 101 to 103 of FIG. 3 are omitted. With the omission of the frame buffer 77, the inner product value (→ N) is stored in the color lookup tables 81 and 83, respectively.
... → L) and only the depth value r are given as addresses. In the present embodiment, it is assumed that even if there are a plurality of figures to be displayed at the same time, their materials are the same. In FIG. 4, the frame buffer 77 of FIG. 3 is omitted for this reason. What is important in FIG. 4 is that the inner product value (→ N
Instead of omitting the frame buffer 76 (FIG. 3) for holding (.fwdarw.H), the stored contents of the color look-up table 81 are different from those of FIG. Expression (1
The specular reflected light component shown in 2) is the inner product (→ N · → H)
Is close to 1, that is, only when the angle α (FIG. 2) formed by the unit normal vector → N and the unit vector of the light source / line-of-sight intermediate direction → H is within a range of 0 to 0. Here, if the angle formed by the light source direction vectors → L and → N is β and the angle formed by → L and → H is δ, then α = δ-β. Also c
osα = (→ N · → H) and cosβ (→ N · → L). Therefore, if the positions of the light source and the viewpoint are fixed, δ becomes constant. Therefore, only for a certain range (→ N · → L) close to β, the specular reflection component proportional to (→ N · → H) is generated. Is a significant value.

For the above reasons, the color look-up table 81 of FIG. 4 previously stores the value of the equation (12) with the equation (1) for the inner product value (→ N · → L) within a certain range.
The value I _ads added to 1) is stored. This allows
Brightness data reflecting the same specular reflected light component as when there are 76 and 82 in FIG. 3 is obtained.

In the color look-up table 83 of FIG. 4, the luminance for one material number of the data of the color look-up table 83 of FIG. 3 is stored at the position corresponding to the depth value r.

In the apparatus shown in FIG. 4, if a graphic of a different material is to be displayed, a color look-up table 8 is used.
This can be realized by changing the contents of 1 and 83 to the brightness of the corresponding material.

In FIG. 4, the outputs I _adsR , I _adsG , I _adsB of the color look-up table 81 and the outputs I
_rR, I _rG, I _rB represents this way the luminance data R obtained, G, and B components.

Another important point in FIG. 4 is that an adder for adding the outputs of the color look-up tables 81 and 83 is not used, and instead the color look-up table 8 is used.
The outputs I _adsR , I _adsG , and I _{adsB of 1} are respectively ₈₄ ,
The video amplifier 9 converts the video signal into an analog video signal by the 5,86 DA converter and further amplifies the video signal.
Output I _rR of the gain of 1-93 color look-up table 83, I _rG, is that allowed to increase in response to the value of I _rB.

As a result, the luminance of the video signal output to the CRT display 90 depends on both the outputs of the color lookup tables 81 and 83. Therefore, it depends on the depth value r, the inner product (→ N · → L) and (→ N · → H).

In this case, the luminance of the video signal is the luminance I depending on the depth value r as in the case of FIGS.
r (equation (8)) and the luminance I depending on the vector → N
_Although it depends on the product of _N (formula (9)), in the case of FIG. 4 as well, a screen similar to the display screen obtained in the case of FIG. 1 or 3 is obtained.

In the case of FIG. 4, the frame buffer 76 and the adders 101 to 103 in FIG. 3 can be omitted, and the circuit is accordingly simpler. In particular, the adders 101 to 1 shown in FIG.
In FIG. 3, the signal delay time must be made sufficiently small, but in FIG. 4, the elimination of such a circuit has a great practical advantage.

[0072]

According to the present invention, in a three-dimensional graphic display device, a change in luminance depending on the direction and the depth value of each display pixel can be controlled at an arbitrary ratio. Display is possible.

In addition, since a result of previously calculating brightness is set in a brightness table for a series of directions and depth values of display pixels and is referred to and added, a light reflection model is calculated for each display pixel. As compared with the case of performing the display processing, the display processing is remarkably speeded up, and the display control of the luminance that changes in both the direction and the depth value of the display pixel can be performed at high speed.

According to the means for enabling the brightness control based on the depth value by adjusting the gain of the video amplifier, there is an advantage that the addition of hardware is small and the display speed is not reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of a display system according to the present invention.

FIG. 2 is a diagram showing various vectors used to calculate the reflection intensity of a three-dimensional figure (object).

FIG. 3 is a block diagram of a second embodiment of the display system according to the present invention.

FIG. 4 is a block diagram of a third embodiment of the display system according to the present invention.

[Explanation of symbols]

30: pixel generation processor, 41, 42: inner product calculation circuit, 51, 59: luminance table, 71 to 73, 75 to 7
9: frame buffer, 74: depth buffer, 81 to
83: color look-up table, 64-66,10
1 to 103... Adders.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-217461 (JP, A) JP-A-61-272872 (JP, A)

Claims (1)

(57) [Claims] 1. A display means and each of display pixels included in a two-dimensional figure obtained by projecting a three-dimensional figure to be displayed on a two-dimensional plane among a plurality of pixels constituting a display screen of the display means. With respect to the display position X, Y of each display pixel, the depth value on the three-dimensional graphic corresponding to the display position, and the luminance code determined depending on the normal direction of each surface of the three-dimensional graphic. A depth buffer that stores and holds the depth value output from the pixel generating means in correspondence with each display position, and the direction dependent luminance code output from the pixel generating means in correspondence with each display position. A color look-up in which a frame buffer that is stored and stored, a depth value from the depth buffer, and a luminance code from the frame buffer are input as reference addresses and converted into color information at each display position. An up table and a DA converter for converting the output of the color look-up table into an analog luminance signal, and displaying on the display means according to the luminance signal output by the DA converter. Three-dimensional graphic display device.