JPS6329891A - Multiple light source shading device - Google Patents

Abstract

PURPOSE:To attain the shading display of an external form of a three- dimensional grapic based on a multiplex light source by forming tables corresponding to the number of light sources, and at the time of finding out luminance, adding values obtained from these tables in accordance with R, G and B. CONSTITUTION:Segment and plane graphics obtained from a processor 200 are applied to an image processor 300 as vertex coordinates and a unit normal vector. The image generating processor 300 calculates the position of a display point, a normal vector, a light source vector, and an intermediate direction vector between the light source and a visual point and the material index of a display object is simultaneously applied from a register 430 to the processor 300. The sum of luminance information read out from luminance tables 510-561 is found out by adders 610-630 in each color component to find out the luminance values or respective dots on patch planes to be respective faces of a similar polyhedral body and the luminance values are written in frame buffers 710-730. The luminance of a CRT monitor 90 is controlled from the frame buffers 710-730 through DA converters 810-830 to attain shading display.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a graphic processing device, and more particularly to a multiple light source shading device that performs shading display of a display object using multiple light sources in three-dimensional graphic processing.

[Conventional technology]

A conventional technique for displaying the outline of a three-dimensional figure with a three-dimensional effect by shading the figure is, for example, disclosed in Japanese Patent Application Laid-Open No.
It is described in 9-223922. In addition, regarding shading based on the light reflection model, J, D
, Foly, A, ”/andDam,' Funda
-mentals Of Interactive
Computer Graphics'.

Addison Wess17 Publishing
Discussed in Compan7.

The principle of shading using a reflection model will be outlined below.

Figure 2 is a schematic diagram of the reflection model introduced by B11nn, where N is the hive normal vector of the reflective surface, L is the unit vector from the reflection point P toward the light source, and ■ is the unit vector from the reflection point P toward the viewpoint. Here, H is a unit vector in the direction of the sum of L and V. Therefore, H is just a part of the angle formed by L and V.

In the figure, the light intensity at the viewpoint is expressed by equation (1).

I=I, to +IP(k, (N reference L)+, (N-
H'l' ) (1) However, ＆: Intensity of ambient light 1: Ambient light reflection coefficient ■,: Intensity of light from the light source 0: Diffuse reflection coefficient, : Direct reflection coefficient n: Surface roughness of object It is a constant between tens and hundreds of quantities that depends on the

In the prior art, equation (1) is divided into two parts: a part consisting of the first term and the second term, and a third term, and the first part is a function of N-L, and the second part is a function of N The brightness for the six values of these inner products is held as a function of -H, and the brightness is immediately calculated by holding a - set of table buttons and searching the table with the inner product value.

FIG. 4 is a block diagram showing the overall configuration of a single light source shading device according to the prior art, in which 1° is a host computer, 20 is a coordinate transformation processor, 30 is a pixel generation processor, 41 and 42 are inner product calculation processors, and 43 is a Material index register, 51 to 56 are brightness tables,
61 to 63 adders, 71 to 73 are frame buffers,
81 to 83 are DA converters, and 9 is a CRT monitor.

In the figure, a coordinate transformation processor 20 receives the coordinates of each vertex of the approximate polyhedron and the nest normal vector from the host computer 10, and rotates the coordinates as necessary.
Performs processing such as parallel movement.

Each figure on one line segment from the processor 20 is generated by the processor 5, which generates one pixel in the form of its vertex coordinates and unit normal vector.
given to 0. The pixel generation processor 30 calculates the position of a display point, a normal vector, a light source vector, and a light source/viewpoint intermediate direction vector. At the same time, the material index of the display object is given from the register 43. This material index is used to select a set of brightness tables having different contents for each material.

The inner product calculation processors 41 and 42 input the normal vector 11 of the approximate polyhedron of the figure and the light source/viewpoint intermediate direction I from the pixel generation processor 30, and calculate the inner product y(i-U) and (π・1), respectively. and register 43
It receives the material index of the display object from and outputs the reference address of the brightness table.

The brightness tables 51 to 56 show brightness coefficients ad corresponding to diffuse reflection and brightness 1. and the red component (R), green component (G), and blue component (B
).

The brightness information read from the brightness tables 51 to 56 is
The sum is calculated for each color component by adders 61 to 63,
As a result, the brightness of each dot on the patch surface, which is each surface of the approximate polyhedron, is found, and this is calculated using the 7 frame buffer 71.
~Write to 73.

From frame buffers 71 to 73, DA'& switch 81 to
The brightness of the CRT monitor 9 is controlled via step 83, and shading display is performed.

[Problem that the invention seeks to solve]

The conventional technology described above does not take into account shading when there are multiple light sources, and has a problem in that shading display using multiple light sources cannot be performed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multiple light source shading device capable of shading the outline of a three-dimensional figure using multiple light sources.

[Means for solving problems]

The above purpose was achieved even though the brightness table in the prior art only had one table for ambient light and diffused light and one table for specular reflection light for each RGB, as shown in Figure 4. On the other hand, this can be achieved by providing as many tables as there are light sources and adding the values obtained from these tables for each RGB when determining the brightness.

[Effect]

When there are multiple light sources, the light intensity at the viewpoint is expressed by equation (2) when Li is the *C vector directed from the reflection point P toward the light source i.

I=I, kll ten ΣI, 1kd(NL,)+ΣI,,
kfl(N - Hi)' (2) However, ■, 1: Intensity of light from light source 1 Here, especially considering the case of two light sources, equation (2) becomes (3
) can be written as the formula.

r==I, ni, +I,, ni, (N −L,) Jukou P
2, (N-L2) +I,, k, (N-H,)' + I, k, (N -H2)'...
- (3) As can be seen from equation (3), the luminance of light at the viewpoint is the sum of the luminance from the first light source and the luminance from the second light source. A brightness table is set for each of the four parts, the part consisting of the first term and the second term, the third term, the fourth term, and the fifth term of equation (3).

For the first table, (N-L,), for the second table (N-L2), and for the third table (N-)(,).

The fourth table is searched by (N-H2) and the luminance factor can be calculated by adding them together.

〔Example〕

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention, and is an example in which there are two light sources, 100V.
i host computer, 200 is coordinate transformation processor%
500 is a pixel generation processor, 410°411.420
, 421 is an inner product calculation processor, 430 is a material index register % 510, 511, 520° 521.5
50,551.540,541.550,551,56
0°561 is a brightness table, 610, 620, 630 are adders, 710.720, 730 are frame buffers,
810, 820, 830 are DA converters, and 90 is a CRT monitor.

In the figure, a coordinate transformation processor 200 receives the coordinates and unit normal vectors of each dot on the approximate polyhedron from the host computer 100, and performs processes such as rotation and translation of the coordinates as necessary. The contents of this process have no direct relation to the present invention, and are detailed in the above-mentioned book by Fo17 et al.

Each figure on one line segment from the processor 20[) is given to the processor 300 in the form of its vertex coordinates and unit normal vector. Pixel generation processor 5004-1
, display point position, normal vector, light source vector, light source
This is to calculate the viewpoint intermediate direction minus miktor. The material index of the display object is given from the register 430.

This material index selects a set of brightness tables whose contents are very different from the material.

The inner product calculation processors 410, 411, 420, and 421 receive the normal vector N of the approximate polyhedron of the figure and the light source vectors L, , L2 . Using the light source/viewpoint intermediate direction vectors H, , H2 as input, inner products (Nt, ), (N-L2), (N-H4), (N
-H2), receives the material index of the display object from the register 430, and outputs the reference address of the brightness table.

The brightness tables 510 to 561 show brightness values corresponding to diffuse reflection corresponding to each one of the inner products. di(i=1.
2) (However, when 1-1, % adi corresponds to the sum of ambient light and diffusely reflected light = see formula (3)) and brightness factor corresponds to direct reflection, 1 is the red component (R), Green component (G)
, blue component (B).

Here, in equation (3), if the light source is sufficiently far from the display object, I and I can be considered to be constant on the display object.

Also, ambient light is not proportional to the number of light sources, so only one need be taken into account at any given time.

Therefore, equation (3) consists of four parts: the first and second terms, the third, fourth, and fifth terms, and each part is treated as a function of a single inner product. It is something that can be done. Therefore, R,G.

It would be sufficient to create 14 tables for each of B.

The brightness information read from the brightness tables 510 to 561 is summed by adders 610 to 63o for each color component, and the brightness of each dot on the patch surface, which is each surface of the approximate polyhedron, is determined and sent to the frame buffer 710. ~Write to 730. Regarding the interpolation of the brightness of patch dots and the writing process to the frame buffer, refer to the above-mentioned Fol)'
Detailed in other books.

Frame buffers 7710, 720, and 730 control the brightness of CRT monitor 9o via DA converters 810 to 830 to perform shading display.

Incidentally, when the surface of the display object figure is composed of parts having several different reflection coefficients, it is sufficient to add as many brightness tables as the number of parts. However, when the number of additional brightness tables becomes too large due to the large number of types, the contents of tables that are used less frequently may be replaced so that they can be used.

〔Effect of the invention〕

As explained above, according to the present invention, by having a plurality of brightness tables, after obtaining the inner product for each pixel, each brightness table is searched using that value.

By calculating the sum of each brightness, it is possible to take advantage of the effect of multiple light sources, and it is possible to perform shading display using multiple light sources, as well as to display shading using multiple light sources when the display figure is made up of multiple parts with different reflection coefficients. It is possible to provide a multi-light source shading device that can perform shading and has excellent functions while eliminating the drawbacks of the prior art described above.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the overall configuration of an embodiment of the present invention, Figure 2 is a schematic diagram of a light reflection model when there is one light source, and Figure 3 is a light reflection model when there are two light sources. FIG. 4 is a block diagram showing the overall configuration of a shading device according to the prior art. 100: Host computer 200: Coordinate conversion processor 300: Pixel generation processors 410-421: Inner product generation processor 430: Registers 510-561: Brightness tables 610-630: Adders 710-730: Frame buffers 810-8.30: DA conversion Device 90: CRT monitor. ,′− 1′

Claims (1)

[Claims] 1. In displaying the outer shape of a three-dimensional figure, as a means for determining the brightness of each point as a function of vectors in the normal direction and light source direction of each point constituting the figure, the method uses the vector inner product. In a multi-light source shading device having a table holding a set of luminance data pre-calculated corresponding to a set of vector dot products of an expected range, searched based on
The table is provided corresponding to each light source, these values are searched by the inner product value for each light source, and the brightness is calculated by the sum of the values, thereby making it possible to display shading of a three-dimensional figure using a plurality of light sources. A multiple light source shading device featuring: 2. The multiple light source shading device according to claim 1, characterized in that when the surface of the three-dimensional figure has different reflection coefficients depending on the part, a brightness data table for the different reflection coefficients is provided. A multiple light source shading device. 3. In the multiple light source shading device according to claim 2, when there are many portions with different reflection coefficients and the table size to be prepared becomes too large, tables that are used less frequently are combined into one. , a multiple light source shading device characterized by having means for withholding the contents when necessary.