JPH04220782A - Three-dimensional image display processing method - Google Patents

Abstract

PURPOSE:To correctly display a transparent object even when the object is multiplexed. CONSTITUTION:In a three-dimensional image display processing method for displaying the transparent object by means of alpha blending method, an opaque Z buffer 3 storing the Z value of a latest opaque object and an opaque picture element value buffer 4 storing the picture element value of the latest opaque object are provided. The Z value of the object to be displayed is compared with the Z value in the opaque Z buffer 3 and when the object to be displayed is further than the latest opaque object, the picture element value of the object to be displayed will not be the object of picture element calculation. When the object to be displayed is closer than the latest opaque object and the object to be displayed is higher in speed than the latest object in a Z buffer 7, the picture element value is restored from the picture element value in a picture element value buffer 8, that in the opaque picture element value buffer 4 and transparency in a alpha, buffer 9 and a new picture element value is calculated based on the picture element of the object to be displayed, the tansparency in the alpha buffer 9 and the restored picture element.

Description

[Detailed description of the invention]

(Table of Contents) Industrial Application Fields (FIG. 8) Conventional Technology (FIGS. 9 to 11) Problems to be Solved by the Invention (FIGS. 12 to 14) Means for Solving the Problems (FIG. 1) Functional Examples (a) Description of one embodiment (FIGS. 12 to 7) (b) Description of other embodiments Effects of the invention

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional image display processing method for displaying transparent objects using an alpha blending method.

With recent advances in hardware, it has become possible for computers to display three-dimensional images at high speed. The Z-buffer method is known as this basic technology. The Z-buffer method is a method for eliminating hidden surfaces caused by overlapping objects when objects placed in three-dimensional space are viewed from a certain perspective, and is especially essential for high-speed three-dimensional image display. It is a great technology.

FIG. 8 is an explanatory diagram of the Z-buffer method.

As shown in FIGS. 8(C) and 8(D), the Z-buffer method uses a Z-buffer 7 that stores the Z value, which is the most recent position in the depth direction of a figure from the viewpoint, for each pixel on the screen. and,
A pixel value buffer 8 is used to store the pixel values of the figure.

As shown in FIG. 8(A), the Z value (position in the depth direction from the viewpoint) of each pixel of the figure to be displayed (here, a triangle is taken as an example) and FIG. ), calculate the pixel value of each pixel of the figure, and if the Z value is closer to the viewpoint than the Z value of the corresponding pixel in the Z buffer 7, then Then, the contents of the corresponding pixels in the pixel value buffer 8 and Z buffer 7 are replaced with the Z value and pixel value of the pixel in the figure to be displayed (Fig. 8
(Bold line parts in (E) and (F)) If the distance is far, the Z value and pixel value are not replaced, so that only the surface or part of the surface that can be seen from the viewpoint is finally displayed.

The disadvantage of this Z-buffer method is that it cannot display transparent objects because it considers objects to be opaque and only determines their context.

[0008] Therefore, there is a need for a three-dimensional display processing technique that can display transparent objects three-dimensionally.

[0009]

2. Description of the Related Art FIG. 9 is an explanatory diagram of the prior art.

As shown in FIG. 9, for displaying a transparent object, pixel information (pixel value, Z value, transparency) corresponding to the object to be displayed is stored for each pixel in the pixel value buffer 8.
There is a method of storing the objects as a list in the order of their appearance, sorting by Z value when information on all objects is collected, and determining pixel values taking into account transparency until an opaque object appears.

[0011] According to this method, three-dimensional images including transparent objects can be displayed correctly, but creating a list requires a huge amount of memory and the list must be sorted by Z value, resulting in a huge amount of data. The drawback is that it requires extensive calculations and is difficult to implement in hardware.

[0012] Therefore, an alpha blending method has been proposed as a method that can quickly provide a sense of transparency, although it may not be possible to display a three-dimensional image including a transparent object correctly. This method uses the Z-buffer method to remove hidden surfaces, but
In addition to the Z buffer, an α buffer is prepared to store the object's transparency, and when displaying a transparent object, the pixel value of the corresponding pixel previously stored in the pixel value buffer 8 is set according to the object's transparency. The pixel values of transparent objects are added.

FIGS. 10 and 11 are explanatory diagrams of the conventional alpha blending method.

As shown in FIG. 10(A), the Z buffer 7
In addition to the pixel value buffer 8 and the
PU) 1 performs alpha blending processing.

For example, as shown in FIG. 10(B), if the Z value is Z
1 transparent object (transparency a = 0.5, pixel value D = 8) is displayed, an opaque object with Z value Z2 (transparency a
= 0.0, pixel value D = 16).

The contents of the Z buffer 7, α buffer 9, and pixel value buffer 8 at this time are those of a transparent object with a Z value of Z1, as shown in FIG. 10(B). One pixel of an opaque object with a Z value of Z2 overlaps with a transparent object with a Z value of Z1, but in this case, the pixel value Db after blending is as follows (1)
Calculated by the formula.

[0017]

[Math 1]

Here, Dt is the pixel value of the transparent object, at is the transparency of the transparent object, and Di is the pixel value of the opaque object.

In areas where transparent objects and opaque objects do not overlap, it is sufficient that the pixel values of the transparent object and the pixel values of the opaque object are displayed as they are, so the Z after alpha blending
The contents of the buffer 7, α buffer 9, and pixel value buffer 8 change as shown in FIG. 10(C).

This process flow is shown in FIG. 11.

Pixel information (X, Y, Z, α, D) of the figure to be displayed is read from the input buffer 2, and the pixel information is transferred to the Z buffer 7.
, α buffer 9, and pixel value buffer 8 at positions corresponding to X and Y, and set them as Z', α', and D', respectively. Flosser 1 compares Z and Z', sets the Z value of Z and Z' that is closer to the viewpoint as Z", sets the α value as α1,
Let the D value be D1, the α value of Z and Z' that is farther from the viewpoint be α2, and the D value be D2. And update transparency α
” is calculated using the following equation (2).

[0022]

[Math 2]

Next, D1 is replaced by Dt in the above equation (1), and a
Substitute α1 for t and D2 for Di to obtain D''. Then, X of Z buffer 7, α buffer 9, and pixel value buffer 8
, Y are updated with Z'', α'', and D''.

[0024] In this way, three-dimensional display of an opaque object through a transparent object such as glass becomes possible.

[0025]

[Problem to be solved by the invention] Figures 12, 13, and 1
4 is a diagram illustrating problems with the conventional alpha blending technology.

After the blending shown in FIG. 10(C) is performed, an opaque object with a Z value of Z3 is mixed with a transparent object with a Z value of Z1 with a Z value of Z2, as shown in FIG. 12(A). When inserted between an opaque object, it may be placed after the opaque object whose Z value is Z2, as shown in FIG. 12(B). In these cases, if the conventional alpha blending method of FIG. 11 is applied, the Z buffer 7, α
Blending processing is performed from the contents of buffer 9 and pixel value buffer 8 and the contents of pixel information of an opaque object whose Z value is Z3, and as shown in FIG. 13(A), the blended pixel value has a Z value of All corresponding pixel values of the object Z1, Z2, and Z3 are reflected.

By the way, the original state of FIG. 12(A) is
As shown in FIG. 13(B), the opaque object whose Z value is Z2 is hidden by the opaque object whose Z value is Z3, and due to the invisible state, the original state of FIG. 12(B) is
As in A), by an opaque object whose Z value is Z2,
An opaque object with a Z value of Z3 is hidden and cannot be seen.

Therefore, the correct display result is as shown in FIG. 12(A).
Then, from the pixel values of a transparent object whose Z value is Z1 and an opaque object whose Z value is Z3, it should be determined as shown in Figure 14 (B), and in Figure 12 (B), the Z value is It should be determined as shown in FIG. 14(C) from the pixel values of a transparent object whose Z value is Z1 and an opaque object whose Z value is Z2.

[0029] In this way, in the conventional alpha blending method, emphasis is placed on high speed with hardware implementation in mind, so regardless of the order of the objects, it is assumed that there is only one object and the processing is performed. , when objects are multiplexed, there is a problem that transparent objects cannot be displayed correctly.

Therefore, in the present invention, even if objects are multiplexed,
An object of the present invention is to provide a three-dimensional image display processing method that can correctly display transparent objects.

[0031]

[Means for Solving the Problems] FIG. 1 is a diagram showing the principle of the present invention.

Claim 1 of the present invention provides a Z buffer 7 that stores a Z value that is the depth position of the most recent object from a viewpoint for each pixel, and stores the transparency of the most recent object for each pixel. It has an α buffer 9, a pixel value buffer 8 that stores the pixel value of each pixel, and a processing unit 1, and removes hidden surfaces by comparing the Z value of the object to be displayed with the Z value of the Z buffer 7. At the same time, a new pixel value is calculated based on the transparency of the α buffer 9 and the pixel value of the object to be displayed. an opaque Z buffer 3 for storing Z values;
An opaque pixel value buffer 4 is provided to store the recent pixel value of the opaque object, and the Z value of the object to be displayed is compared with the Z value of the opaque Z buffer 3 to determine whether the object to be displayed is If the object is further away than the recent opaque object, the pixel value of the object to be displayed is not subject to pixel value calculation, and if the object to be displayed is closer than the recent opaque object, and the object to be displayed is The object is the Z buffer 7
If the object is further away than the recent object, the pixel value buffer 8
The pixel value is restored from the pixel value of the object to be displayed, the pixel value of the opaque pixel value buffer 4, and the transparency of the α buffer 9, and the pixel value of the object to be displayed and the transparency of the α buffer 9 are restored. A new pixel value is calculated based on the restored pixel value.

[0033] Claim 2 of the present invention provides the following in claim 1:
When the object to be displayed is a transparent object, a new pixel value is calculated based on the pixel value and transparency of the object to be displayed, the transparency of the α buffer 9, and the restored pixel value, and the The transparency of the object to be displayed and the above α
A new transparency is calculated from the transparency of the buffer 9, and a new pixel value is calculated based on the new pixel value, the new transparency, and the pixel value of the opaque pixel value buffer 4.

[0034] Claim 3 of the present invention provides the following in claim 1:
If the object to be displayed is closer than the recent opaque object, and if the object to be displayed is closer than the recent object in the Z buffer 7, the object to be displayed is a transparent object. Then, the pixel value is restored from the pixel value of the pixel value buffer 8, the pixel value of the opaque pixel value buffer 4, and the transparency of the α buffer 9, and the pixel value and transparency of the object to be displayed are determined. , calculating a new pixel value based on the transparency of the α buffer 9 and the restored pixel value, calculating the new transparency from the transparency of the object to be displayed and the transparency of the α buffer 9,
A new pixel value is calculated based on the new pixel value, the new transparency, and the pixel value of the opaque pixel value buffer 4.

[0035]

[Action] Considering the overlap between transparent and opaque objects,
As for opaque objects, once they appear, all objects behind them are invisible from that point of view. That is, the displayed image only needs to have information up to the opaque object closest to the viewpoint. Therefore, in claim 1 of the present invention, an opaque Z buffer 3 that stores the Z value of the most recent opaque object and an opaque pixel value buffer 4 that stores the pixel value of the most recent opaque object are provided.

[0036] If an opaque object that is displayed later is farther from the viewpoint than an opaque object that is displayed earlier,
If you do not blend the pixel values of the subsequent opaque object,
Transparent objects can be displayed correctly. Therefore, the Z value of the object to be displayed is compared with the Z value of the opaque Z buffer 3, and if the object to be displayed is further away than the recent opaque object, the pixel value of the object to be displayed is It is no longer included in the value calculation.

Furthermore, if the opaque object to be displayed later is closer to the viewpoint than the opaque object to be displayed first, if the blended pixel values can be recalculated, the transparent object can be displayed correctly. Therefore, if the object to be displayed is closer than the recent opaque object, and if the object to be displayed is farther than the recent object in the Z buffer 7, the pixel value in the pixel value buffer 8 and the opaque pixel value buffer 4 Restore the pixel value from the pixel value of and the transparency of α buffer 9,
A new pixel value is calculated based on the pixel value of the object to be displayed, the transparency of the α buffer 9, and the restored pixel value.

According to claim 2 of the present invention, even when the object to be displayed is a transparent object, multiple transparent objects can be displayed in consideration of the transparency of the transparent object.

According to claim 2 of the present invention, even if the object to be displayed is a transparent object closest to the viewpoint, multiple transparent objects can be displayed in consideration of the transparency of the transparent object.

[0040]

[Embodiment] (a) Description of one embodiment FIG. 2 is a block diagram of one embodiment of the present invention. In the figure, the same parts as shown in FIGS. 1 and 10 are indicated by the same symbols. be.

In FIG. 2, the Z buffer 7, α buffer 9, pixel value buffer 8, opaque Z buffer 3, and opaque pixel value buffer 4 are composed of one memory.

FIGS. 3 and 4 are three-dimensional image processing flow diagrams of an embodiment of the present invention, FIG. 5 is an explanatory diagram of an embodiment of the present invention, and FIG. 6 is a three-dimensional image processing flow diagram of an embodiment of the present invention. Explanatory diagram,
FIG. 7 is an explanatory diagram of the case where the object is inserted between a transparent object and an opaque object.

■The processor 1 reads the pixel information (X, Y, Z, α, D) of the object to be displayed from the input buffer 2, reads the contents of the position corresponding to X and Y in the opaque Z buffer 3, Let's say Zu.

(2) Processor 1 compares Z and Zu. If Z>Zu, as shown in FIGS. 5A and 6, the object to be displayed is behind (far away from) the opaque object and is hidden by the opaque object, so all buffers 3 and 4 are ,7,
Do not change the contents of 8 and 9 and return to step (■).

■ If the object to be displayed is not behind (far away from) the opaque object, the processor 1 determines the positions corresponding to X and Y of the Z buffer 7, α buffer 9, pixel value buffer 8, and opaque pixel value buffer 4. Read the contents of Z' respectively.
, α', D', and Du. Furthermore, processor 1
and Z' are compared. If Z>Z', Fig. 5 (B), (C
), the object to be displayed is between a transparent object and an opaque object, so proceed to step ■, and if Z<Z', display in Figure 5 (
As shown in D) and (E), since the object to be displayed is in front of the transparent object, the process proceeds to step 2 (B in FIG. 4).

(2) If the object to be displayed is between a transparent object and an opaque object, first restore the pixel values. Restored pixel value D
1 is calculated using the following equation (3) using D' of the pixel value buffer 8, Du of the opaque pixel value buffer 4, and α' of the α buffer 9.

[0047]

[Math 3]

Next, the processor 1 determines whether the transparency α of the object to be displayed is not "0" (opaque). If α is not "0" (opaque), the object to be displayed is transparent (as in Figure 5 (C)), so step ■ (Figure 4
Proceed to step A).

On the other hand, when α is "0" (opaque), the object to be displayed is opaque (as shown in FIG. 5(B)), so as shown in FIG. 7, the restored pixel values D1, A new pixel value D'' is calculated using the following equation (4) using α' of the α buffer 9 and the pixel value D of the object to be displayed.

[0050]

[Math 4]

This equation is the same as equation (1). Then, the contents of the positions corresponding to X and Y in the pixel value buffer 8, opaque Z buffer 3, and opaque pixel value buffer 4 are updated with new pixel values D'', Z, and D, respectively, and the process returns to step (2).

■If α is not “0” (opaque), the object to be displayed is transparent, so two transparent objects are lined up as shown in FIG. 5(C), so the new pixel value D” Calculate the integrated transparency α”.

First, the restored pixel value D1, α of the α buffer 9
', the pixel value D of the object to be displayed, and the transparency α, a new pixel value D'' is calculated using the following equation (5).

[0054]

[Math 5]

Next, using α' of the α buffer 9 and the transparency α of the object to be displayed, the integrated transparency α'' is calculated using the following equation (6).

[0056]

[Math 6]

Furthermore, using the new pixel value D'', the integrated transparency α'', and the pixel value Du of the opaque pixel value buffer 4, the new pixel value D
” is calculated using the following equation (7).

[0058]

[Math 7]

[0059] Then, the α buffer 9 and the pixel value buffer 8
The contents of the positions corresponding to X and Y are updated with the integrated transparency α'' and the new pixel value D'', respectively, and the process returns to step (2).

(2) In step (2), if the object to be displayed is in front of the transparent object, the processor 1 determines whether the transparency α of the object to be displayed is not "0" (opaque). If α is not "0" (opaque), the object to be displayed is transparent (as in FIG. 5(E)), and the process proceeds to step (2).

On the other hand, when α is "0" (opaque), the object to be displayed is opaque (as shown in FIG. 5(D)), and other objects are hidden by this, so the Z buffer 7 , the contents of the positions corresponding to X and Y of the α buffer 9, opaque Z buffer 3, and opaque pixel value buffer 4, respectively, are the Z value Z, transparency α, Z value Z, and pixel value D of the object to be displayed.
Update with and return to step ■.

■In step ■, if α is not "0" (opaque), the object to be displayed is transparent (as shown in FIG. 5(E)), so the restored pixel is value D
Calculate 1. Since the object to be displayed is transparent, two transparent objects are lined up as shown in Figure 5(E).
A new pixel value D'' and integrated transparency α'' are calculated.

First, the restored pixel value D1, α of the α buffer 9
', the pixel value D of the object to be displayed, and the transparency α, a new pixel value D'' is calculated using the following equation (8).

[0064]

[Math. 8]

Next, using α' of the α buffer 9 and the transparency α of the object to be displayed, the integrated transparency α'' is set to (
6) Calculate using the formula.

Furthermore, using the new pixel value D'', the integrated transparency α'', and the pixel value Du of the opaque pixel value buffer 4, the new pixel value D
” is calculated using equation (7) in step (■).

[0067] Then, the contents of the positions corresponding to X and Y of the Z buffer 7, α buffer 9, and pixel value buffer 8 are calculated using the Z value Z of the object to be displayed, the integrated transparency α'', and the new pixel value D'', respectively. Update and return to step ■.

In this way, even if objects are multiplexed, transparent objects can be displayed correctly in three dimensions.

(b) Description of other embodiments Although the processing unit is a processor and is implemented by a program, it may also be implemented by hardware.

Although the present invention has been described above with reference to examples, various modifications can be made within the scope of the present invention, and these are not excluded from the scope of the present invention.

[0071]

[Effects of the Invention] As explained above, according to the present invention,
It has the following effects.

■An opaque Z buffer and an opaque pixel value buffer are provided, and if the object to be displayed is farther than the nearest opaque object in the opaque Z buffer, it will not be subject to pixel value calculation. Depending on the pixel value, it is possible to prevent the transparent object from being displayed incorrectly and to correctly display the transparent object in three dimensions.

■If the object to be displayed is closer than the nearest opaque object in the opaque Z buffer, but further away than the nearest object in the Z buffer, the pixel values are restored and alpha blending is performed, so that Depending on the pixel value, it is possible to prevent the transparent object from being displayed incorrectly and to correctly display the transparent object in three dimensions.

[0074] Furthermore, the high speed of the alpha blending method can be maintained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is a three-dimensional processing flow diagram of an embodiment of the present invention.

FIG. 4 is a three-dimensional processing flow diagram of an embodiment of the present invention.

FIG. 5 is an explanatory diagram of an embodiment of the present invention.

FIG. 6 is an explanatory diagram of an embodiment of the present invention when inserted after an opaque object.

FIG. 7 is an explanatory diagram of an embodiment of the present invention when inserted between a transparent object and an opaque object.

FIG. 8 is an explanatory diagram of the Z buffer method.

FIG. 9 is an explanatory diagram of a prior art.

FIG. 10 is an explanatory diagram of a conventional alpha blending method.

FIG. 11 is an explanatory diagram of a conventional alpha blending method.

FIG. 12 is a diagram illustrating problems in the prior art.

FIG. 13 is a diagram illustrating problems in the prior art.

FIG. 14 is a diagram illustrating problems in the prior art.

[Explanation of symbols]

1 Processing unit (processor) 3. Opaque Z buffer 4. Opaque image source value buffer 7 Z buffer 8 Pixel value buffer 9 α buffer

Claims (3)

[Claims] 1. A Z buffer (7) that stores the Z value that is the depth position of the recent object from the viewpoint for each pixel, and an α buffer (7) that stores the transparency of the recent object for each pixel.
9) and a pixel value buffer (8) that stores the pixel value of each pixel.
) and a processing unit (1), which performs hidden surface removal by comparing the Z value of the object to be displayed with the Z value of the Z buffer (7), and also determines the transparency of the α buffer (9). In an image processing device that displays a transparent object by calculating a new pixel value based on the pixel value of the object to be displayed, an opaque Z buffer (3 ) and an opaque pixel value buffer (4) that stores the pixel value of the recent opaque object, and compares the Z value of the object to be displayed with the Z value of the opaque Z buffer (3), If the object to be displayed is farther than the recent opaque object, the pixel value of the object to be displayed is not subject to pixel value calculation, and the object to be displayed is closer than the recent opaque object. and if the object to be displayed is farther than the recent object in the Z buffer (7), the pixel value in the pixel value buffer (8) and the pixel value in the opaque pixel value buffer (4) The pixel value is restored from A three-dimensional image display processing method characterized by calculating a value. 2. When the object to be displayed is a transparent object, the pixel value is updated based on the pixel value and transparency of the object to be displayed, the transparency of the α buffer (9), and the restored pixel value. A pixel value is calculated, a new transparency is calculated from the transparency of the object to be displayed and the transparency of the α buffer (9), and the new pixel value, the new transparency, and the pixel of the opaque pixel value buffer (4) are calculated. 2. The three-dimensional image display processing method according to claim 1, wherein the new pixel value is calculated based on the pixel value. 3. If the object to be displayed is closer than the recent opaque object, and if the object to be displayed is closer than the recent object in the Z buffer (7), the object to be displayed is When the object is a transparent object, the pixel value of the pixel value buffer (8), the pixel value of the opaque pixel value buffer (4), and the α buffer (9)
The pixel value is restored from the transparency of the object to be displayed, a new pixel value is calculated based on the pixel value and transparency of the object to be displayed, the transparency of the α buffer (9), and the restored pixel value, A new transparency is calculated from the transparency of the object to be displayed and the transparency of the α buffer (9), and a new pixel is calculated based on the new pixel value, the new transparency, and the pixel value of the opaque pixel value buffer (4). 2. The three-dimensional image display processing method according to claim 1, further comprising calculating a value.