JPS63191286A - Smooth shading system - Google Patents

Abstract

PURPOSE:To shorten a smooth shading processing time by dividing a smooth shading subject graphic into plural triangles. CONSTITUTION:For instance, a partial triangle P1AB of a triangle P1P2P3 undergoes the smooth shading via scanning. Thus the smooth shading is possible for all points of other triangles AP2C, BCP3 and CBA by performing the arithmetic processes via subtractors 4 and 5 and an adder 6. Therefore a scanning process is given to the triangle P1AB only and the smooth shading processing time is shortened. The processing time is also shortened even with another type of pattern by dividing the graphic into triangles and applying the smooth shading process in the same way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a smooth shading method for realistically displaying a graphic surface displayed on a screen.

(Prior Art) Conventionally, for example, a triangle P1°P2 . P
When performing smooth shading of P1, P2.3, perform the scan indicated by the arrow. The color brightness at all points on the triangular plane is determined by interpolation from the position, color brightness, and Z value of each point in P3, and the color brightness of each point on the triangular plane is changed depending on the position to perform smooth shading processing. It is carried out. Therefore, since it is necessary to interpolate colors on all planes during smooth shading, there is a drawback that smooth shading processing becomes slow.

(Problems to be Solved by the Invention) In the conventional smooth shading method described above, all points on the triangular plane are scanned and the brightness of the color at each point is determined by interpolation, so the smooth shading process takes a long time. There was a drawback that it took a while. SUMMARY OF THE INVENTION In order to eliminate the above-mentioned drawbacks, the present invention aims to provide a smooth shading method that can perform smooth shading of an entire plane by scanning only a portion of a triangular plane.

[Structure of the Invention] (Means for Solving the Problems) The present invention is directed to an apparatus that performs smooth shading processing by determining the color brightness of all points of a triangle from the color brightness of each vertex constituting the triangle. a smooth shading means for dividing a smooth shading target figure into a plurality of triangles, and performing smooth shading processing on all points of the triangle by scanning one of the triangles over the entire area; and the smooth shading processing. a coefficient calculating means for calculating a coefficient for each remaining triangle that makes all points forming the triangle subjected to the above process correspond one-to-one to all points forming each remaining triangle; and calculation means for performing smooth shading processing on each of the remaining triangles by calculating the brightness of the color of all the points forming each of the remaining triangles from all the points using the coefficients.

(Operation) In the smooth shading method of the present invention, the smooth shading means divides the smooth shading target figure into a plurality of triangles, and scans one of the triangles over the entire area, thereby smoothing all points of this triangle. A shading process is performed and the result is given to the calculation means. The coefficient calculation means calculates coefficients for each of the remaining triangles to make all the points forming the triangle subjected to the smooth shading process correspond one-to-one to all the points forming each remaining triangle, and sends these coefficients to the calculation means. give.

The calculation means uses the coefficients to calculate the color brightness of all points forming each remaining triangle from all points forming the triangle subjected to smooth shading processing, and performs smooth shading processing on each remaining triangle. .

(Example) An example of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing an embodiment of a smooth shading processing device to which the smooth shading method of the present invention is applied. 1.2 is a midpoint calculator that calculates the smooth shading information of the midpoint between the two vertices from the xy coordinates, color brightness, and z value that are the smooth shading information of the vertices of the triangle; 3 is the midpoint calculator 1 and 2. Smooth shading is performed by calculating smooth shading information on this triangular plane for all points from the smooth shading information of the vertex and the two midpoints of a triangle formed by a given midpoint and one vertex. The smooth shading device 4 and 5 calculate the coefficients α and β for transferring the smooth shading information of all points on the triangular plane on which the smooth shading has been performed to the other three triangular planes, and calculate the coefficients α and β for transferring the smooth shading information of all points on the triangular plane on which the smooth shading has been performed, and A subtractor having a shift circuit that creates smooth shading information of a corresponding point on a square triangular plane from smooth shading information of an arbitrary point above, 6 is smooth shading information of all points on the triangular plane that have undergone the smooth shading. The coefficient M for transferring to the other three triangular planes
7 is an adder having a shift circuit that calculates the value and creates smooth shading information of a corresponding point on another triangular plane from the smooth shading information of an arbitrary point on the triangular plane that has undergone smooth shading; A comparator that compares the binary value with the binary value of the corresponding x and y coordinate point of the 2 buffer, and opens the gate 10 only when the former is larger than the latter. 8 stores the Z value for all points on the display screen. 9 is a frame buffer for storing graphic information subjected to smooth shading, and 10 is a gate for controlling whether or not the brightness of the color of the smooth shading target point is supplied to the frame buffer.

Next, the operation of this embodiment will be explained. First, the smooth shading target figure is triangle P1P shown in Figure 2.
2P3. In addition, A, B, and C are used. The midpoint calculators 1 and 2 have smooth shading information at each point of the triangle P1P2P3 (×1.yl, zl, 11
), P2(X2+'/2.Z2.f2), P3 (
X3. 'l/3°Z3,13) is given. As a result, the midpoint calculator 1 calculates the smooth shading information of the midpoint A from the smooth shading information P1, P2,
A((X1+X2)/2, (yl+y2)/2,
(zl +Z2)/2, (i 1+i 2)/
2) is calculated. The midpoint calculator 2 also uses the smooth shading information P1. Smooth shading information from P3 to midpoint B, B((X1+X3)/2, (
yl +y3) / 2, (Z1+Z trigram) /2, (+
1+i 3 )/2 ) is calculated. The smooth shading information of the midpoints A and B calculated as described above is provided to the smooth shading device 3 and the adder 6. In the smooth shading device 3, the given P
Scanning of the entire triangle P1AB is performed as usual based on the smooth shading information of each point of l, A, and B, and smooth shading of all points of this triangle is performed,
Smooth shading information for all points of the triangle P1AB is output. On the other hand, the subtracter 4 uses the smooth shading information p1. From p2, the coefficient α[(XIX2)/2, ('i/I V2)/2, ('i/I V2)/2, (
zl-Z2)/2, (11-1□)/2) are calculated and stored. The subtracter 5 also uses smooth shading information P1. From P3, a coefficient β((X
l −x3 ) /2, (yl−y3)/2, (zl−
z3 )/2, (i 1i 3 )/2) are calculated and stored. Furthermore, the adder 6 calculates a coefficient M(2
l, 2yIIl, 2zII1121. ) is calculated and stored. However, (xm "m ' zm, i) is ((2
x1 +X2 +X3 )/2, (2y1+ y2 +
y3 )/2, (2z1+22 +23 )/2, (
2i 1+i 2 113)/2).

Next, the subtractor 4.5.6 is the smooth shading device 3.
The smooth shading information of all points of triangle P1AB output from triangle AP C and triangle BC are respectively
P3, by converting the smooth shading information of all points of triangle CBA using the coefficients α, β, and M,
Perform smooth shading for each triangle. For example, when performing smooth shading of triangle AP2C in subtractor 4, the coefficient α is subtracted from the smooth shading information (xp, yp, zl), i p ) of point P of triangle P1A8 output from smooth shading device 3. and the smooth shading information PcX(X, -X (Z-yp'
J cr, Z p Z a, i p i a ) are determined, and this smooth shading information is output. Similarly, in the subtractor 5, the coefficient β is subtracted from the smooth shading information of the P point of the triangle P1AB, and the smooth shading information Pβ(X, -Xβ) of the corresponding Pβ point of the triangle BCP3.

yI)-yβ, zl)-2β, i, -iβ) is obtained, and this smooth shading information is output. Further, in the adder 6, by subtracting the smooth shading information of the point P of the triangle P1AB from the coefficient M, the smooth shading information of the corresponding PT point of the triangle CBA is obtained.

2y -y, 2zIII-zp, 2iIl, -i,)
is determined as p, and this smooth shading information is output.

Triangle P output from smooth shading device 3
The x1y coordinates of smooth shading information of all points of 1AB are input to 2 buffer 8 and frame buffer 9, and Z
The value is input to a comparator 7, and the i value (color brightness) is input to a gate 10. In addition, the x1y coordinates of the smooth shading information of all points of the triangles AP2C1BCP3 and CBA output from the subtracter 4.5 and the adder 6, respectively, are stored in the Z buffer 8.
, is input to the frame buffer 9, and the Z value is input to the comparator 7.

A 1 value (color brightness) is input to gate 10. Comparator 7
Then, compare the two values of the smooth shading point with the two values in the two buffer 8 corresponding to this point (given by xy coordinates), and if the former two values are larger than the Z value of the latter, the comparator 7 selects the gate 10. is released and the i value of the smooth shading point is written to the corresponding point (given in xy coordinates) of the 7-frame buffer 9, resulting in the triangle P1P2P
All points of 3 are subjected to hidden surface processing and smooth shading by the comparator 7, buffer 8 and gate 10, and are written into the frame buffer 9.

According to this embodiment, if smooth shading of triangle P1AB, which is a part of triangle P1P2P3, is performed by scanning in the conventional manner, smooth shading of all points of other triangles AP2C2BCP3 and CBA is performed by subtracters 4 and 5 and adder 6. This can be done by performing arithmetic processing. Therefore, since scanning is performed only on the triangle P1AB in FIG. 4, the smooth shading processing time can be shortened.

In addition, in the above embodiment, an example was explained in which one large triangle is divided into four parts and smooth shading processing is performed, but other shapes can also be divided into triangles and smooth shading processing similar to the above is performed. For example, processing time can be reduced compared to the conventional example.

[Effects of the Invention] As described above, according to the smooth shading method of the present invention, smooth shading of the entire plane can be performed by scanning only a part of the triangular plane.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a smooth shading processing device to which the smooth shading method of the present invention is applied, FIG. 2 is a diagram showing an example of a figure to be subjected to smooth shading, and FIG. 3 is the same as that shown in FIG. 1. FIG. 4 is a diagram illustrating a conventional smooth shading method. 1.2... Midpoint calculator 3... Smooth shading device 4.5... Subtractor 6... Adder 7... Comparator 8... 2 buffer 9... Frame buffer 10・・・Gate agent Patent attorney Nori Chika Ken Yudo Sanno − C Engineering ° ゛go

Claims (1)

[Claims] A device that performs smooth shading processing by calculating the color brightness of all points of the triangle from the color brightness of each vertex constituting the triangle, divides the smooth shading target figure into a plurality of triangles, and calculates the color brightness of one of the triangles. a smooth shading means that performs smooth shading processing on all points of the triangle by scanning the entire area of the triangle; and a smooth shading means that performs smooth shading processing on all points of the triangle; a coefficient calculating means for calculating a coefficient for each remaining triangle that has a one-to-one correspondence with the coefficient; 1. A smooth shading method, comprising: calculation means for performing smooth shading processing on each remaining triangle by calculating using .