JPH04137075A - Image reproducer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention is a method for converting shape data of a three-dimensional object created in advance into two.
The present invention relates to an image generation device that performs visualization by projecting onto a dimensional display surface.

"Prior Art" In order to visualize the shape data of a 3D object created by various systems such as 3D CAD and 3D shape measuring equipment, this shape data is projected onto a 2D display surface,
A method of creating dimensional images is often used. At this time, in order to give the created image a three-dimensional effect, the brightness of the surface of the shape data is calculated by giving conditions such as the light source, viewpoint, surface characteristics, etc., and the brightness information is assigned to the projected surface to create shading. A method of attaching is used.

In addition, in the case of a three-dimensional object with a curved surface, the general f-/'
JLP-, Asshi, 1 1 ふ;;dhFJN? j5cho H
→Because it involves a lot of trouble, it is usually expressed approximately as a set of microplanes (hereinafter referred to as "patches"). In this case, when shading is performed using the method described above, discontinuities in brightness will occur at the boundaries of the patches on the projected display surface to which adjacent patches are assigned different brightnesses because the brightness is different. .

Such a phenomenon results in a result contrary to the physical property that the original object is an object having a smooth three-dimensional curved surface.

Therefore, in order to prevent discontinuities in brightness within the projected curved surface, the brightness or normal vector at the vertices of the patch is determined, and the brightness within the batch is determined by linearly interpolating the brightness or normal vector at these vertices. A method is proposed. An example of such a linear interpolation method is to calculate the normal vector at each point in the patch by linear interpolation, and calculate the brightness from this normal vector.
The Gouraud shading method is generally used, in which the brightness at each vertex of the patch is determined from the normal vector at this vertex, and the brightness at each point within the punch is determined by linear interpolation of the brightness at each vertex.

``Problems to be Solved by the Invention'' However, even though the conventional shading method described above is modulo, the brightness within the patch changes linearly, that is, linearly, continuously, but at the boundary of the patch, the brightness changes. The curvature of the change becomes discontinuous, and stripes called "matsuha" or "bands" occur in these areas, creating an unnatural appearance.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an image generation device that can generate a two-dimensional image in which brightness changes smoothly even at the boundaries of patches.

``Means for Solving the Problems'' Therefore, the present invention provides an image generation device that generates two-dimensional image data from shape data of a three-dimensional object. input means a into which the shape data of is input, and vertex brightness calculation means to calculate the normal vector and brightness at the apex of the microplane. Based on at least one of the normal vector and the brightness obtained by the projection means C for projecting the shape data onto the display surface and the vertex brightness calculation means, a high-order interpolation function is used to calculate the shape data corresponding to the pixel. A three-dimensional brightness calculation means d that calculates the normal vector or brightness of a point on a microscopic surface, and a pixel brightness calculation means that calculates the brightness of a corresponding pixel on a display surface based on the result of the three-dimensional brightness calculation means d. The above-mentioned problem is solved by providing an output means f for outputting the result calculated by the pixel brightness calculation means e as two-dimensional image data.

Here, it is preferable that the interpolation function has a continuous property up to its second derivative.

"Operation" In the present invention, based on the shape data of a three-dimensional object whose surface is approximated by a set of a plurality of microplanes, which is input by the input means a, the vertex brightness calculation means calculates the The shape data is projected onto a two-dimensional display surface on which the normal vector and brightness are calculated. Next, based on at least one of the normal vector and the brightness obtained in step 1.8b, the three-dimensional brightness calculation means d calculates the normal of the point on the microsurface corresponding to the pixel using a high-order interpolation function. After the vector or brightness is calculated, the 3
Based on the results of the dimensional brightness calculation means d, the pixel brightness calculation means e calculates the brightness of the corresponding pixel on the display screen.

The result calculated by the pixel brightness calculation means e is outputted as two-dimensional image data by the output means f.

In addition, the above-mentioned "means for solving the problem" and "action"
Although the description has been made using the reference numerals shown in FIG. 1 in the above section, it goes without saying that the present invention is not limited to the configuration shown in FIG.

"Embodiments" Examples of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing an image generation device that is an embodiment of the present invention. In the figure, reference numeral 1 indicates an input means such as a magnetic disk device, 2 indicates a storage means including a RAM (random write memory), 3 indicates a display means such as a display, and 4 indicates a CPU (central processing means). 5 is an output means consisting of a magnetic disk or the like.

Input means 1 receives shape data from another system capable of creating shape information of a three-dimensional object, such as a three-dimensional CAD, a three-dimensional modeling system, or a three-dimensional shape measuring device.

This other system creates shape information by approximating a three-dimensional curved surface with a plurality of microscopic planes called batches. The input means 1 is connected to the arithmetic processing means 4, and the shape data input by the input means 1 is output to the arithmetic processing means 4.

The storage means 2 is connected to the calculation processing means 4, and the storage means 2 temporarily stores the shape data of the three-dimensional object inputted by the input means 1, and also stores the shape data of the three-dimensional object inputted by the input means 1.
The calculation results are also temporarily stored.

The display means 3 is controlled by the arithmetic processing means 4, and the display means 3 displays the shape data of the three-dimensional object inputted by the input means 1 on the screen, and also displays the calculation result by the arithmetic processing means 4 on the screen. to be displayed.

The arithmetic processing means 4 calculates the normal vector and brightness at the apex of the micro-uneven plane, and projects the shape data onto a two-dimensional display surface formed by a plurality of pixels arranged in a plane. , further calculating the normal vector or brightness of a point on the microsurface corresponding to the pixel using a high-order interpolation function based on at least one of the calculated normal vector or brightness at the vertex of the microplane, Based on this result, it has a function of calculating the brightness of the corresponding pixel on the display screen.

The output means 5 is connected to the arithmetic processing means 4, and the output means 5 outputs two-dimensional image data based on the arithmetic results of the arithmetic processing means 4.

Next, the operation of the image generation device of this embodiment will be explained with reference to the flowchart shown in FIG.

(2) Shape Data Input First, shape data of a three-dimensional object is input using the input means 1 (step 5PI). Here, as mentioned above, 3
Another system that can create shape information of dimensional objects is the 4th system.
As shown in the figure, the surface S of a three-dimensional object is divided into batches P, , (
It is approximated by a set of rectangular minute planes called 1≦1≦n, 1≦j≦m, where i, j, n, and m are natural numbers).

In these systems, shape information is stored at each vertex V of the batch.
The batch consists of vertex information having three-dimensional coordinate values, edge information indicating the connection relationship between vertices, and surface information indicating all edges constituting the batch.

In other words, each system is common in terms of shape information. However, in a system that mathematically creates 3D shape information such as a 3D modeling system, the coordinate values of the vertices (of a batch) of the created shape information are true values, but the 3D shape measurement device In a system that creates three-dimensional shape information from measured values, it must be noted that the coordinate values of the vertices (of the batch) include measurement errors. Here, as shown in FIG. 4, it is assumed that shape information consisting of nXm batches has been created. This shape information is input into the input means 1 as shape data from the system.

At the same time, environmental information such as the surface characteristics of the object, the position of the light source, and the position of the viewpoint is also input via the input means 1.

The shape data etc. input in this way are temporarily stored in the storage means 2 via the arithmetic processing means 4. Also,
The input shape data is displayed on the screen via the display means 3 as necessary.

■Calculation of normal vectors and brightness of patch vertices The calculation processing means 4 calculates the normal vectors and brightness of the vertices of all batches based on the input shape data (step 5P2). The normal vector is the average of the normal vectors of the batches that exist around the vertex (in this embodiment, there are four batches around the vertex as shown in FIG. 4). The brightness may be calculated using a phono reflection model using environmental information such as the surface characteristics of the object, the position of the light source, and the position of the viewpoint, which are input at the same time as the normal vector of the vertex and the shape data.

In the following description, the normal vector and brightness at the vertex V of the patch are assumed to be H4, L, and I, respectively.

(3) Projection onto a two-dimensional display surface The calculation processing means 4 projects a three-dimensional object (i.e., a collection of patches) made up of the input shape data onto a display surface (step 5P3).

The patch projection method will be explained. As shown in FIG. 5, when considering a patch P 2 , first, the intersection points between the display surface and the straight line connecting each vertex of the patch P 2 and a predetermined viewpoint are found. In this embodiment, since the patch is formed in a rectangular shape, four points of intersection are determined. These intersection points are defined as patch P1. are sequentially connected by line segments according to the connection information of the vertices (that is, the edge information described above).

The area surrounded by these line segments becomes a patch projected onto the display surface. Repeat the above steps,
Project all the patches that make up the three-dimensional object.

(4) Intra-patch brightness calculation calculation processing means 4 colors the inside of the projected patch. Here, as shown in FIG. 6, the display surface is composed of a plurality of squares called pixels arranged in rows on the surface. Therefore, coloring inside the patch can be done by providing color information to all pixels within the projected patch.

First, the arithmetic processing means 4 selects one pixel in the projected patch to be colored, and finds a point on the patch in the three-dimensional space that corresponds to the selected pixel (step 5P4).
As shown in Fig. 5, the points on the punch in the three-dimensional space are connected to the straight line connecting the pixels in the projected batch and the viewpoint,
It can be determined as an intersection with a patch in three-dimensional space.

Next, color the points on this patch (Step 5P)
5). The coloring of a point on a patch can be determined by multiplying the brightness of the point by color information unique to the object. In addition, as shown in FIG. 7, the brightness of a point is determined by the vertices IV, kl i-1/ of 3×3 patches including the patch where the intersection exists.
2≦h≦i+(1-1)/2+1, j-1/2≦≦
Luminance sequence IL corresponding to j+(1-1)/2+1 l
h kl 1-1/2≦h≦i+(1-1)/2
+1, j-1/2≦to≦j+(1-1)/2 +1
It can be determined by using a value of 1 and applying a high-order interpolation function. However, l represents the dimension of the interpolation function. Examples of high-order interpolation functions that can be used include cubic spline interpolation, parabolic blending interpolation, Bezier curve interpolation, cubic B-spline interpolation, and the like.

In particular, cubic spline interpolation and parabolic blending interpolation have the property that, on a curved surface representing interpolated luminance, the luminance value at the patch vertex matches the luminance value at the patch vertex calculated in step SP2. There is. In other words, these interpolation functions have the property of always passing through the coordinate values to be interpolated.

Therefore, these interpolation functions are suitable for shape information created by a mathematical method such as a three-dimensional modeling system. On the other hand, in Bezier curve interpolation and cubic B-spline interpolation, on a curved surface representing interpolated brightness, the brightness value at the vertex of the patch and the brightness value at the patch vertex determined in step SP2 usually do not match. In other words, these interpolation functions attempt to interpolate between coordinate values to be interpolated using a curved surface as smooth as possible, and are suitable for shape information based on measured values that include errors. In this example, the cubic B expressed by the following equation is used.
Assume that spline interpolation is used.

No(t)=(-1/6)t3+(1/2)t2-(1
/2)t+1/6N, (t)=(1/2)t3-t2+
2/3N2(t)=(-1/2)t3+(1/2)t2
+(1/2)t+ 176N3(t)=(116)t3 By applying the high-order interpolation function in this way,
High-order continuity of brightness is guaranteed, and continuity at the patch boundaries is satisfied. For example, in the parabolic blending interpolation method, class C1 is continuous, while in other interpolation methods, class C2 is continuous.
1gL continuous flow is guaranteed.

Then, when coloring at each point of the patch in the three-dimensional space is completed, this coloring data is projected onto a two-dimensional display screen using the same method as in step SP3, and is used as coloring data for pixels on the display screen (step SP3). 5P6).

Finally, the two-dimensional image information on the display surface is displayed on the screen via the display means 3, and if necessary, is written as image data to the output means 5 and output (step 5P7). In this embodiment, since the brightness within a patch is interpolated using a high-order interpolation function, high-order continuity is guaranteed not only within the patch but also at its boundaries. This eliminates the occurrence of phenomena such as the generation of Matsuha bands due to discontinuities in the image, and it is possible to obtain images with smooth changes in brightness.

Note that the details of the image generation device of the present invention are not limited to the above-mentioned embodiments, and various modifications are possible. - For example, in the above embodiment, an interpolation function was applied to the luminance, but instead of the luminance sequence, a high-order interpolation function is applied to the normal vector sequence, and the phono reflection model is applied to this. The brightness can also be determined by In this case, compared to the case where luminance is interpolated, a high-quality image that is closer to reality can be obtained in highlight processing, etc., but the normal vector is
It is a dimensional vector, and requires about three times the amount of calculation for interpolation. Furthermore, since a phono reflection model is calculated for each pixel, it is necessary to select hardware that can withstand this calculation load.

"Effects of the Invention" As explained in detail above, according to the present invention, an image generation device that generates two-dimensional image data from shape data of a three-dimensional object is approximated by a set of a plurality of microplanes. an input means into which shape data of the three-dimensional object is input; a vertex brightness calculation means to calculate the normal vector and brightness at the apex of the microplane; and a plurality of pixels arranged in a plane. A projection unit that projects the shape data onto a two-dimensional display surface, and a high-order interpolation function that corresponds to the pixel based on at least one of the normal vector and brightness obtained by the vertex brightness calculation unit. three-dimensional brightness calculation means for calculating the normal vector or brightness of a point on the microsurface; and pixel brightness calculation means for calculating the brightness of a corresponding pixel on the display surface based on the result of the three-dimensional brightness calculation means. , and an output means for outputting the results calculated by the pixel brightness calculation means as two-dimensional image data, so that high-order continuity is guaranteed not only within the micro-uneven plane but also at the boundary thereof, and the above-mentioned Unlike conventional methods, phenomena such as the generation of Matsuha bands due to discontinuities at the boundaries of microplanes do not occur, and images with smooth changes in brightness can be obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic block diagram showing the overall configuration of the present invention, Figure 2 is a schematic block diagram showing the overall configuration of the present invention.
The figure is a block diagram showing an image generation device that is an embodiment of the present invention, FIG. 3 is a flowchart for explaining the operation of the embodiment, and FIGS. 4 to 7 are for explaining the operation of the embodiment. This is a diagram for 1...Input means, 2...Storage means, 3
...Display means, 4... Arithmetic processing means,
5... Output means, P... Patch (microplane) SF3... Vertex brightness calculation means, SF3...
... Projection means, SP4-SP5 ... Three-dimensional brightness calculation means, SF3 ... Pixel brightness calculation means.

Claims (2)

[Claims] (1) an input means into which shape data of a three-dimensional object whose surface is approximated by a set of a plurality of microplanes; a vertex brightness calculation means for calculating the normal vector and brightness at the apex of the microplane; based on at least one of a normal vector or brightness obtained by a projection means for projecting the shape data onto a two-dimensional display surface formed by arranging pixels in a plane, and the vertex brightness calculation means, three-dimensional brightness calculation means for calculating the normal vector or brightness of a point on the microsurface corresponding to the pixel using a high-order interpolation function;
Pixel brightness calculating means for calculating the brightness of a corresponding pixel on the display screen based on the result of the three-dimensional brightness calculating means, and output means for outputting the result calculated by the pixel brightness calculating means as two-dimensional image data. An image generation device equipped with (2) The image generation device according to claim 1, wherein the interpolation function has a continuous property up to its second derivative.