JP2019040419A - Image processing apparatus and program - Google Patents

Abstract

To provide an image processing apparatus capable of reducing the load in image processing such as a deformation operation, and a program.SOLUTION: An image processing apparatus, which is configured to divide a virtual space forming a virtual polygon model into virtual cells of a predetermined polygonal shape to form the polygon model, accepts value data distributed in a virtual space to be processed, determines a value for the position of each vertex of the polygonal shape of the cell on the basis of the value data, sets side identification information for identifying each side element, with sides not overlapping each other as side elements, among the sides of each cell, specifies side identification information of the side element at which the vertex of the polygon passing through the cell is located on the basis of values corresponding to the positions of vertices at both ends of each side element, and generates information representing the polygon model using the specified side identification information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image processing apparatus and a program for processing medical images and the like.

  In recent years, for example, a technique for processing image data obtained from, for example, a medical diagnostic apparatus (such as a CT apparatus) to express a tissue such as a blood vessel as a three-dimensional polygon model and visualize it as a three-dimensional image is widely known. It has been. As such processing for modeling and visualization, for example, in the medical field, image processing called a marching cube method is generally used (for example, Patent Document 1).

JP 2012-245374 A

  However, in the image processing using the conventional marching cube, visualization is possible, but the following problems arise when performing a deformation operation of the tissue polygon model in order to perform a simulation during surgery.

  That is, in the normal marching cube method, tetrahedral cells are arranged in a matrix in a virtual space, and a numerical value (for example, a luminance value of the image data) is set in the virtual space based on a plurality of image data. Then, for each of the cells, it is determined whether or not a plane having a predetermined value (isosurface) is included, and information for specifying the isosurface is generated for the cell that is supposed to include the isosurface. .

  Here, a pair of cells adjacent to each other includes sides (called common sides) arranged at the same position. Specifically, as illustrated in FIG. 10, in the cells A and B adjacent to each other, the sides A1 to A4 constituting the bottom surface of the cell A and the sides B5 to B8 constituting the top surface of the cell B are common sides. Included as However, in the normal marching cube method, since the isosurface is set independently for each cell, for example, when it is determined that the isosurface set for the cell A crosses the point Ax on the side A1, The isosurface will also cross the point Bx on the side B5 of the cell B which is the common side with respect to the side A1. Here, although the point Ax and the point Bx are the same point in the virtual space, in the marching cube method, processing is performed for each cell. Therefore, the points Ax and Bx are identified as different points and used for processing. Is done.

  This is not usually a problem when used only for visualization. However, when a vertex editing operation such as a deformation operation is performed on this polygon model, the corresponding point Bx is changed when the position of the point Ax is changed. By searching, the position of the point Bx must be changed in the same manner as the point Ax.

  For this reason, the processing load of the deformation operation increases, and it may be difficult to perform processing such as performing vertex editing operations in real time. Also, when processing for integrating vertices at the same coordinates prior to the vertex editing operation, the processing load is large.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image processing apparatus and a program that can reduce an image processing load such as vertex editing operation.

  The present invention for solving the problems of the above-described conventional example is an image processing apparatus for forming a polygon model by dividing a virtual space forming a virtual polygon model into virtual cells having a predetermined polygon shape, Means for accepting value data distributed in the virtual space to be processed; means for determining a value for each vertex position of the polygonal shape of the cell based on the value data; and Of these, sides that do not overlap each other are set as side elements, side identification information for identifying each side element is set, and the cell passes through the cell based on the values corresponding to the vertex positions at both ends of each side element. Means for identifying edge identification information of the edge element where the vertex of the polygon to be positioned is located, and polygon model generation means for generating information representing the polygon model using the identified edge identification information. Information of the polygon model represented with the one in which it was decided to be subjected to predetermined processing including visualization and modification operations.

  According to the present invention, it is possible to reduce an image processing load such as a deformation operation.

It is a block diagram showing the example of a structure of the image processing apparatus which concerns on embodiment of this invention. It is a functional block diagram showing an example of the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing showing the example of the cell and edge element which the image processing apparatus which concerns on embodiment of this invention sets. It is explanatory drawing showing the example of a setting of temporary vertex identification information by the image processing apparatus which concerns on embodiment of this invention. It is a flowchart figure showing the example of operation of the image processing device concerning an embodiment of the invention. It is explanatory drawing showing the operation example of the image processing apparatus which concerns on embodiment of this invention. It is another explanatory drawing showing the example of operation of the image processing device concerning an embodiment of the invention. It is explanatory drawing showing contrast with the process by the image processing apparatus which concerns on embodiment of this invention, and the process of a prior art example. It is explanatory drawing showing the effect of the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing showing the setting method of the vertex in the conventional process.

  Embodiments of the present invention will be described with reference to the drawings. As illustrated in FIG. 1, the image processing apparatus 1 according to the embodiment of the present invention includes a control unit 11, a storage unit 12, an operation unit 13, a display unit 14, and an interface unit 15.

  The control unit 11 is a program control device such as a CPU, and operates according to a program stored in the storage unit 12. In the present embodiment, the control unit 11 divides a virtual space that forms a virtual polygon model into virtual cells having a predetermined polygonal shape to form a polygon model, and information on the polygon model And a predetermined process of visualization and vertex editing operation (deformation operation, etc.) using.

  Here, in the process of forming the polygon model, the control unit 11 accepts value data distributed in the virtual space to be processed. This value data is, for example, image data obtained by a medical device such as CT or MRI. Further, the control unit 11 specifies a value for each position of each vertex of the polygonal shape of the cell based on the value data, and among the sides of each cell, the sides whose positions do not overlap with each other are used as side elements. Set side identification information that identifies each side element, and based on the values corresponding to the positions of the vertices at both ends of each side element, the side element through which the polygon passes (the intersection of this polygon and the side element is the vertex of the polygon) Is specified). Then, the control unit 11 generates information representing the polygon model using the specified edge identification information. The specific processing contents of the control unit 11 will be described later.

  The storage unit 12 stores a program executed by the control unit 11. This program may be provided by being stored in a computer-readable and non-transitory recording medium and stored in the storage unit 12. In the present embodiment, the storage unit 12 also operates as a work memory of the control unit 11.

  The operation unit 13 is a keyboard, a mouse, or the like, and accepts a user instruction input and outputs the content of the instruction input to the control unit 11. The display unit 14 is a display or the like, and displays and outputs information according to an instruction input from the control unit 11.

  The interface unit 15 is an interface such as a USB (Universal Serial Bus), and receives data from an external device and outputs the data to the control unit 11. The interface unit 15 may output information instructed to an external device in accordance with an instruction input from the control unit 11.

  Here, the operation of the control unit 11 of the present embodiment will be described. As illustrated in FIG. 2, the control unit 11 according to the present embodiment executes a program stored in the storage unit 12 to functionally include a polygon model generation unit 20 and a drawing processing unit 30. It is configured to include. Here, the polygon model generation unit 20 includes a data receiving unit 21, a cell setting unit 22, a side element setting unit 23, a temporary vertex identification information acquisition unit 24, and a polygon model setting unit 25.

  In one example of the present embodiment, the data receiving unit 21 of the polygon model generating unit 20 receives image data obtained by a medical device such as CT or MRI. These image data generally include a plurality of images and can express a three-dimensional shape related to a tissue in a human body. A method for obtaining pixel values (value data distributed in a virtual space to be processed) at each point in a three-dimensional space from image data obtained by CT, MRI or the like in this manner is widely known. Therefore, detailed explanation here is omitted.

  The cell setting unit 22 sets a virtual cell having a predetermined polygonal shape in a space where a pixel value is set (a virtual space to be processed). Specifically, here, the virtual space is a regular hexahedron-shaped space having a size of L × L × L, and the vertex of any one of the regular hexahedrons including the origin is defined as the three hexagonal sides of the regular hexahedron including the origin. Assume that the XYZ orthogonal coordinate system is set with the directions as the X, Y, and Z axis directions, respectively. The cell setting unit 22 is, for example, a regular hexahedron having a size of l × l × l (where l is a divisor of L) and the arrangement direction is the X, Y, and Z axis directions. Arrange the cells to match. In the following description, the cell at the origin is expressed as (0, 0, 0), and the adjacent cell sharing the surface with the surface having the normal line in the X-axis direction of this cell is (1, 0, 0). And so on. That is, a cell located at the origin at the ξ-th in the X-axis direction, the η-th in the Y-axis direction, and the ζ-th in the Z-axis direction is represented as (ξ, η, ζ). Also, in the figure, the lower left point on the near side is the origin, the vertical upper direction is the Z-axis positive direction, the right direction is the X-axis positive direction, and the far-side direction is the Y-axis positive direction.

  The cell setting unit 22 sets unique cell identification information for each cell. Specifically, this cell has a cubic (regular hexahedron) shape, and the cell setting unit 22 arranges the cubic shaped cells in a virtual space in a three-dimensional matrix without a gap. The cell setting unit 22 determines a value corresponding to the position of each vertex of the cell based on the value data received by the data receiving unit 21 and records the value.

  The side element setting unit 23 sets side identification information for identifying each side element by using, as side elements, sides whose positions do not overlap among the sides of the three-dimensional shape of the cell. When the cell is specifically a cube, the side element setting unit 23, as illustrated in FIG. 3, uses side identification information of sides 0 to XI belonging to the cubic cell (in this description, to distinguish it from a code). For convenience, numerals other than 0 are indicated by Roman numerals, but may be managed by Arabic numerals or the like in the processing of the control unit 11, predetermined vertices (for example, the bottom of the cell cube vertices (Z-axis direction)) Of the surface having the normal to the side closer to the origin), the three orthogonal sides (side 0, FIG. 3) sharing the point where the X and Y coordinate values are the smallest (P in FIG. 3). Let III, VIII) be edge elements. Thus, the side IX of the cell A in FIG. 3 is expressed as a side element VIII of the cell B adjacent to the right side (X-axis positive side), and the side IV of the cell A is on the upper side (Z-axis positive side). It will be expressed as side element 0 of the adjacent cell C. Here, among the sides parallel to the X-axis of the bottom surface, the sides 0, I, II, III, and the top surface (counterclockwise when viewed from above (Z-axis positive side) in order from the side closer to the origin) Of the sides parallel to the X axis in the surface having the normal line in the Z-axis direction, the counterclockwise when viewed from above (the Z-axis positive side) in order from the side closer to the origin. Sides IV, V, VI, and VII around, the side parallel to the Z axis from point P is side VIII, and the Z axis is on the X axis positive side of the near side (the side having sides 0, IV, and VIII) The side parallel to the side IX, the side parallel to the Z-axis on the positive Y-axis side of the right side surface (the side having the sides I, V, IX) is the side X, and the end of the hexahedron different from these sides 0 to X One side is designated as side XI (FIG. 3).

  Further, in the virtual space to be processed, the sides I, II, IV, V, VI, VII, and X of the cells at the X-axis positive end, the Y-axis positive end, and the Z-axis positive end IX, X, and XI may be treated as not existing.

  The vertex temporary identification information acquisition unit 24 specifies the edge identification information of the edge element where the vertex of the polygon is located. Specifically, the temporary vertex identification information acquisition unit 24 compares a value corresponding to each vertex of the cell with a predetermined value (a value at a position corresponding to the surface of the polygon). It is determined whether the object is inside or outside the solid defined by the polygon model, and the result of the determination is recorded for each vertex of the cell.

  Then, the temporary vertex identification information acquisition unit 24 sequentially selects each cell as a target cell, and 256 indicates whether the vertex of the cell is inside or outside the solid represented by the polygon for the selected target cell. It is determined which one of the corresponding patterns (substantially 15 patterns for symmetry) corresponds to the polygon (for example, a triangle) corresponding to the determined pattern, the polygon and the target cell. Identify points that intersect with sides. Since this method is the same as the processing in the conventional marching cube method, a detailed description thereof is omitted here. At this stage, the temporary vertex identification information acquisition unit 24 identifies the polygon to be drawn, issues polygon identification information unique to each polygon, and records the issued polygon identification information.

  In the present embodiment, the temporary vertex identification information acquisition unit 24 identifies, for each polygon specified here, a point where the polygon intersects the side element of the target cell (the vertex of the polygon on the side element of the target cell). Temporary identification information (information for temporarily identifying a vertex of a polygon on the side element of the cell of interest) is issued. At this time, one of the characteristic features in this embodiment is that instead of using edge identification information for each cell as temporary identification information for temporarily identifying the vertex of this polygon, the cell of interest or its neighbor The edge identification information for specifying the edge element of the cell to be used is used. Here, the edge identification element includes cell identification information for specifying a cell to which the edge element belongs and edge identification information.

  That is, as illustrated in FIG. 4, specifically for the target cell α, the cell β adjacent to the upper side in the drawing, the cell γ adjacent to the right side in the drawing, and the cell γ are adjacent to the upper side. When the cell δ is arranged, it is determined that the two vertices P and Q shown in FIG. 4 of the cell of interest α are determined to be inside the solid and the other vertices are determined to be outside the solid. . At this time, the two polygons (triangles) A and B are polygons existing in the cell of interest, but in this embodiment, as temporary identification information representing the vertices of these triangles (intersections with the sides of the cells) Assume that cell identification information and edge identification information for identifying edge elements for each cell are used.

  Therefore, in the example of FIG. 4, the temporary vertex identification information acquisition unit 24 records the polygon A as having each vertex on the sides 0, III, and VIII of the cell α. Further, the temporary vertex identification information acquisition unit 24 records that the polygon B has each vertex on the side 0 of the cell β, the side VIII of the cell γ, and the side III of the cell δ. Further, the vertex temporary identification information acquisition unit 24 specifies another polygon C different from the polygons A and B in the cell γ when the adjacent cell γ is processed as the target cell. One vertex of the polygon C is recorded as being on the side VIII of the cell γ. That is, one of the vertices of the polygon B and one of the vertices of the polygon C are specified by the same temporary identification information (information that is assumed to be in the side VIII of the cell γ).

  As described above, in the present embodiment, for each polygon, the common vertices are first abstracted using cell identification information and edge identification information for identifying edge elements so that the same temporary identification information is given. (In actual rendering, each vertex is identified by a unique number or the like different from each other, and is expressed as “abstract” here). That is, the temporary identification information specified here functions as an abstract identifier.

  The polygon model setting unit 25 generates information representing the polygon model by using the edge identification information specified by the vertex temporary identification information acquisition unit 24 for each polygon. In other words, the polygon model setting unit 25 identifies, for a plurality of polygons specified by the vertex temporary identification information acquisition unit 24, temporary identification information indicating each vertex of each polygon (this information identifies the cell identification information and the side element for each cell). Polygon model information including the edge identification information to be generated).

  In the present embodiment, using the polygon model information generated here, predetermined processing including visualization and deformation operations is executed. Specifically, the control unit 11 first converts the temporary identification information of each polygon included in the polygon model information into vertex identification information (information representing the position of the vertex, so-called real identification information) used for actual drawing. .

  This conversion process can be performed by issuing identification information such as a unique number or character string for each temporary identification information as vertex identification information. At this time, in order to perform processing such as drawing, it is necessary to associate the polygon and vertex identification information representing the vertex. Therefore, in the present embodiment, the control unit 11 achieves this association process as follows.

  That is, the control unit 11 performs a histogram pyramid (Christopher Dyken, et.al., High-speed Marching Cubes using Histogram Pyramids, Computer Graphics Forum, Vol. 27, issue 8, December 2008, pages as processing of the polygon model setting unit 25. The temporary identification information is converted into vertex identification information using the same method as in 2028-2039), and the vertex identification information obtained by the conversion is associated with the polygon identification information using the histogram pyramid method.

  Specifically, the control unit 11 converts the temporary identification information into the vertex identification information by the same method as the histogram pyramid. That is, the control unit 11 sequentially selects each cell as a target cell, and selects the side elements of the selected target cell in a predetermined selection order (for example, in the order of side 0, side III, side VIII if the cell is a regular hexahedron). Then, the number of vertices of the polygon on the side element is counted and accumulated. And the control part 11 records the sum (accumulated value) of the value obtained by the said count about each side element as a count value (base level count value) about an attention cell.

  Furthermore, the control unit 11 sets a plurality of groups of a plurality of adjacent cells (for example, n × n × n cells adjacent to each other) in order from a predetermined position, and sets the set groups to the first block For each of the first-stage blocks, the sum of the number of vertices of the polygon on the side element in the cell belonging to the first-stage block, that is, the sum of the base level count values for the cells belonging to the first-stage block is And recorded as a count value (level 1 count value) for the first block.

  Here, the predetermined position may be, for example, the cell (0, 0, 0) at the origin of the virtual space. The order of group formation is such that n × n × n cells including the origin cell are grouped, and then n × n × n cells including cells adjacent to the group in the X-axis direction are grouped. ... and when there are no cells adjacent in the X-axis direction, return to X = 0 and group n × n × n cells including cells adjacent in the Y-axis direction into the already formed group. Then, n × n × n cells including cells adjacent to the group in the X-axis direction are selected as a group. When this process is repeated and there are no cells adjacent in the Y-axis direction, X = 0 and Y = 0 are returned, and n × n × n cells including cells adjacent in the Z-axis direction in the already formed group Are repeated from the process of forming a group while moving in the X-axis direction (so to speak, grouping may be performed in the order of a three-dimensional scan line). By this processing, each cell is included in the group in order.

  The control unit 11 is a group of a plurality of (i-1) -th stage (i is an integer of i> 1) blocks (for example, adjacent to each other) adjacent to each other in the order of formation from the predetermined position. 2 × 2 × 2 (i−1) -th stage block group) is set. Then, the control unit 11 sets the set group as the i-th block and calculates the sum of the number of vertices of the polygon on the side element in the cell belonging to the i-th block to the count value for the i-th block ( The process of recording as (level i count value) is executed while incrementing i = 2, 3,... Until the number of blocks becomes less than a predetermined number (for example, until grouping becomes impossible). Repeat until less than x2 or “1”. This stage is hereinafter referred to as the final level for convenience. Here, the group formation order is the same as the cell group formation order.

  The control unit 11 further adds the sum of the number of vertices of the polygon on the side element in the cell belonging to the block in the block unit recorded here, or on the side element in the cell in the recorded cell unit. With reference to the value of the sum of the number of vertices of the polygon, the provisional identification information of the vertices of the polygon is converted into vertex identification information used for actual drawing processing.

  That is, the control unit 11 performs the following processing for each temporary identification information of the vertexes of the polygon. The control unit 11 acquires the cell identification information and the side element identification information, which are temporary identification information to be converted, and includes the cell identified by the acquired cell identification information. Identify blocks in level block units.

  The control unit 11 specifies the (N−1) -th stage block included in the target block with the specified final level (N-th stage) block as the target block. The control part 11 specifies the block in which the cell identified by the acquired cell identification information is contained among the specified Nk step block (an integer of k = 0, 1,..., N−1). The control unit 11 selects the block including the cell identified by the acquired cell identification information while selecting the (Nk-1) -th block included in the target block at the N-k-th block in the order of formation. The value of the sum of the number of vertexes of the polygon assigned to the blocks selected so far (excluding the block itself including the cell identified by the acquired cell identification information) is accumulated. This accumulated value is recorded as a preliminary value for the (N−k−1) th block. The control unit 11 sets a block including a cell identified by the acquired cell identification information as a target block of the (Nk−1) -th stage block. And the control part 11 specifies the Nk-2 step block (when k <N-1) contained in the block of interest of this Nk-1 step block. The control unit 11 repeats this process while incrementing k by “1” until k = N−1.

  When k = N−1 (when the first-stage group including the cell identified by the acquired cell identification information is found), the control unit 11 selects the cells in the first-stage group that have been found in the order of formation. The value of the sum of the number of vertices of the polygon for the selected cell (excluding the cell itself identified by the acquired cell identification information) until the cell identified by the acquired cell identification information is selected. Is accumulated. This accumulated value is recorded as a preliminary value for the first block.

  Further, the control unit 11 selects the side elements in the cell identified by the acquired cell identification information in the order of selection, until the side element identified by the side element identification information acquired together with the cell identification information is selected. Accumulate the sum of the number of polygon vertices on the selected side element. This accumulated value is recorded as a side element preliminary value.

  The control unit 11 uses the acquired cell identification information and the side element identification as the side element preliminary value recorded in this process and the value represented by the sum of the preliminary values (i = 1, 2,... N−1) of the i-th block. Output as vertex identification information corresponding to temporary identification information specified by the information. Thereby, each of the temporary identification information is associated with the serial number vertex identification information.

  For each polygon identified by the recorded polygon identification information, the control unit 11 acquires vertex identification information of each vertex of the polygon. Since this process can be executed by the conventional histogram pyramid method, a detailed description thereof is omitted here.

  The drawing processing unit 30 of the control unit 11 uses the polygon model information generated in this way, and a set of polygon identification information and vertex identification information for identifying each vertex of the polygon identified by the polygon identification information. , Draw each polygon. The processing in the drawing processing unit 30 can be executed by a method similar to the conventional method because a set of each vertex of each polygon and vertex identification information has already been obtained. One of the characteristic features of this embodiment is that the vertex identification information set at this stage is inherent to the set of cell identification information and side element identification information defined by excluding duplication. Therefore, vertices at the same point in the virtual space have the same vertex identification information.

  Therefore, even when the control unit 11 executes a process of deforming a polygon (when moving a vertex, deleting a vertex, or the like), the vertex identified by the predetermined vertex identification information is transformed and the vertex identification information is used. Since it is only necessary to draw a polygon having the identified vertex, there is no need to search for a vertex identified by another identifier that was at the same position as the vertex that was moved or deleted. Efficiency can be improved, and real-time deformation and drawing processes are facilitated.

  Furthermore, in the process of the control unit 11 of the present embodiment, the process of setting the temporary identification information can be performed for each cell without referring to the execution result in other cells, and the vertex identification information is obtained from the temporary identification information. The process of conversion to can also be executed for each temporary identification information without referring to the processing result relating to the other temporary identification information. The process of associating the polygon identification information with the vertex identification information also uses the histogram pyramid process, so it can be executed independently for each polygon (without referring to processes related to other polygons), and parallelization is easy. It has become. Furthermore, although there is a loop process in the process of determining the temporary identification information and the conversion to the vertex identification information, it is not necessary to execute a completely different process depending on the conditional branch, and the processing load is reduced.

  The image processing apparatus according to the present embodiment has the above configuration and operates as follows. In the following description, for the sake of explanation, the virtual space is not a three-dimensional space but a two-dimensional space. Note that generality is not lost even if the dimensions are changed in this way.

  In this example, the image processing apparatus 1 accepts value data distributed in a virtual space to be processed as shown in FIG. 5 (S1). This value data is, for example, image data obtained by a medical device such as CT or MRI. Based on this value data, the image processing apparatus 1 specifies a value for each position of each vertex of the polygonal shape of the cells arranged in the virtual space (S2).

  The image processing apparatus 1 sets side identification information for identifying each side element by using, as side elements, sides whose positions do not overlap each other among the sides of each cell (FIG. 6). Here, since the virtual space is a two-dimensional space, the cell is, for example, a square. Therefore, the left side of the square (referred to as side III) and the lower side (referred to as side 0) are used as the side elements of each cell. In FIG. 6, the horizontal axis is the X axis (right is positive), and the vertical axis is Y (lower is positive). The cell identification information of each cell has the upper left corner as the origin (0, 0), the cell identification information of the cell having the vertex at this origin (the cell at the upper left corner) is “0”, and the cell having the vertex at this origin The cell identification information of the cell arranged at the xth in the X-axis direction and the yth cell in the Y-axis direction (the cell at the position (x, y)) is represented by an integer (xmax × y + x + 1). Note that xmax is the number of cells arranged in the X-axis direction (“8” in FIG. 6).

  The image processing apparatus 1 specifies the side identification information of the side element through which the polygon passes based on the values corresponding to the vertex positions at both ends of each side element of each cell (S3). In other words, the image processing apparatus 1 uses the marching cube method process to obtain the value corresponding to each vertex of the cell specified in process S2 and the value specified in advance (the value at the position corresponding to the polygon surface). A comparison is made to determine whether each vertex of each cell is inside or outside a solid defined by the three-dimensional polygon model, and the result of the determination is recorded for each cell vertex. Then, the image processing apparatus 1 sequentially selects each cell as a target cell, and for the selected target cell, the cell pattern has 15 patterns indicating whether the vertex of the cell is inside or outside the solid represented by the polygon. It is determined which pattern corresponds, and a polygon (for example, a triangle) corresponding to the determined pattern is specified, and a point (vertex of the polygon) where the polygon and the side of the target cell intersect is specified.

  Further, the image processing apparatus 1 issues polygon identification information unique to each polygon, and records the issued polygon identification information.

The image processing apparatus 1 also identifies temporary identification information (on the side element of the target cell) that identifies a point where the identified polygon intersects the side element of the target cell (the vertex of the polygon on the side element of the target cell). Information that temporarily identifies the vertex of a polygon is issued (S4). This temporary identification information will be described using the two-dimensional example illustrated in FIG. 6. In the cell identified by the cell identification information “9” (the cell at the position (1, 1)), the isosurface is an edge. 0 and side I, but each of these points is represented using the side element of each cell.
Side 0 of cell identification information “9”
Side III of the cell identification information “10” (the cell at the position (2, 1))
Accordingly, the image processing apparatus 1 issues and records two pieces of {cell identification information “9”, side 0} and {cell identification information “10”, side III} as temporary identification information.

  When attention is paid to the cell identified by the cell identification information “10”, the image processing apparatus 1 uses {cell identification information “10”, side III}, {cell identification information “3”, side as temporary identification information. 0} are issued and recorded.

  Thus, conventionally, the vertex of {cell identification information “9”, side I} and the vertex of {cell identification information “10”, side III} at the same position are identified as different vertices. Somehow, according to the method of the present embodiment, this position point is expressed (abstract) as common {cell identification information “10”, side III}, and common identification information is assigned.

  In this way, the image processing apparatus 1 performs the processing for each cell, and the vertex of the polygon in the cell on any side in the cell is determined by the side element identification information for identifying the side element in any cell. Represent and record, and generate polygon model information. Then, the image processing apparatus 1 executes predetermined processing including visualization and deformation operations using the generated polygon model information.

  In order to execute this predetermined process, the image processing apparatus 1 first converts the temporary identification information related to the vertices of each polygon included in the polygon model information into vertex identification information used for actual drawing (S5). .

  The image processing apparatus 1 sequentially selects each cell as a target cell, and selects the side elements of the selected target cell in a predetermined selection order (for example, the order of side 0, side III of the cell) on the side element. Accumulate while counting the number of vertices of the polygon. Then, the image processing apparatus 1 records the sum (accumulated value) of the values obtained by counting each side element as a count value (base level count value) for the target cell (FIG. 7A). .

  For convenience of explanation, the examples in FIGS. 6 and 7 do not match. That is, the polygon example in FIG. 6 is different from the polygon example in FIG.

  Furthermore, the image processing apparatus 1 sets a plurality of groups of a plurality of adjacent cells (for example, 2 × 2 cells adjacent to each other) in order from a predetermined position (the origin O in FIG. 7A) ( In FIG. 7A, groups are distinguished by solid lines). Then, the image processing apparatus 1 sets the set group as the first block, and for each of the first block, the sum of the number of vertices of the polygon on the side element in the cell belonging to the first block, that is, the first block The sum of the base level count values for the cells belonging to the first block is recorded as the count value (level 1 count value) for the first block (FIG. 7B).

  Here, 2 × 2 cells including the origin cell are grouped, and then 2 × 2 cells including cells adjacent to the group in the X-axis direction are selected as a group. When there are no cells adjacent in the direction, return to X = 0, group 2 × 2 cells including cells adjacent in the Y-axis direction into the already formed group, and again adjoin this group in the X-axis direction Select 2 × 2 cells including cells as a group. By this processing, each cell is included in the group in order.

  The image processing apparatus 1 sets a plurality of first-stage block groups adjacent to each other (for example, a group of 2 × 2 first-stage blocks adjacent to each other) in the order of formation from a predetermined position (see FIG. 7 (b) also distinguishes groups with solid lines). Then, the image processing apparatus 1 uses the set group as the second-stage block, and calculates the sum of the number of vertices of the polygon on the side element in the cell belonging to the second-stage block as the count value for the second-stage block. It is recorded as (level 2 count value) (FIG. 7C).

  Next, the image processing apparatus 1 sets a group of a plurality of second-stage blocks adjacent to each other (for example, a group of 2 × 2 second-stage blocks adjacent to each other) in the order of formation from a predetermined position. (Groups are also distinguished by solid lines in FIG. 7C). Then, the image processing apparatus 1 uses the set group as the third-stage block, and calculates the sum of the number of vertices of the polygon on the side element in the cell belonging to the third-stage block as the count value for the third-stage block. It is recorded as (level 3 count value) (FIG. 7 (d)). Here, the number of third-stage blocks is “1”, and further grouping is impossible, so this third stage is set as the final level.

  Next, the image processing apparatus 1 acquires cell identification information and side element identification information, which are temporary identification information, for each temporary identification information of the vertexes of the polygon, and includes a cell identified by the acquired cell identification information. Then, the block in the block unit of the final level generated by the above processing is specified.

  Here, since there is only one block at the final level, the second-stage block included in the target block is specified with this block as the target block for any temporary identification information. The image processing apparatus 1 specifies a block including a cell identified by the acquired cell identification information among the specified second-stage blocks. An example in which vertex identification information is generated for the side element of cell identification information “24” and the vertex at “side 0” will be described below.

  In this example, the image processing apparatus 1 specifies a second block included in the target block with a single block of the last block (third block) as a target block. In the example of FIG. 7, since the target block of the third stage block includes all the blocks of the second stage block, all of the second stage blocks are specified.

  The image processing apparatus 1 selects the blocks identified in the second stage block in the order of formation, and selects the blocks (acquired cell identifications) selected until the block including the cell identified by the obtained cell identification information is selected. The value of the sum of the number of vertexes of the polygon assigned to the cell (excluding the block itself including the cell identified by the information) is accumulated.

  The cell of the cell identification information “24”, which is an example here, is included in the upper right block in the second-stage block (which cell is included in which block is recorded for each block when the block is formed). Therefore, it is selected until a block including a cell identified by cell identification information “24” is selected in the order of formation. The only block that is left is the upper left block. Therefore, the image processing apparatus 1 records the sum value “9” of the number of polygon vertices assigned to the upper left block as a preliminary value of the second block.

  Further, the image processing apparatus 1 specifies the first stage block included in the upper right block of the second stage block including the cell of the cell identification information “24”. Here, the image processing apparatus 1 specifies blocks in the third column and the fourth column of the first row of the first-stage block, and the third column and the fourth column of the second row. The image processing apparatus 1 selects the blocks identified in the first-stage block in the order of formation, and selects the blocks (acquired cell identifications) selected until the block including the cell identified by the obtained cell identification information is selected. The value of the sum of the number of vertexes of the polygon assigned to the cell (excluding the block itself including the cell identified by the information) is accumulated.

  Since the cell of the cell identification information “24” as an example here is included in the block of the fourth column of the second row in the first block, it is identified by the cell identification information “24” in the order of formation. The block selected until the block including the cell to be selected is the third column in the first row of the first block, the blocks in the fourth column, and the third column in the second row. It becomes a block. Therefore, the image processing apparatus 1 records the sum “6” of the number of vertexes of the polygon “3”, “1”, “2” assigned to these blocks as a preliminary value for the first block. To do.

  Furthermore, the image processing apparatus 1 specifies a cell (base level) included in the block of the first stage block including the cell of the cell identification information “24”. Here, the cells “23”, “24”, “31”, and “32” are specified by the cell identification information. The image processing apparatus 1 selects the cells specified here until the cell identified by the acquired cell identification information is selected while selecting the cells specified here in the order of block formation (in ascending order of cell identification information). Accumulate the sum of the number of polygon vertices assigned to.

  Since only the cell having the cell identification information “23” is selected until the cell having the cell identification information “24”, which is an example here, is selected, the image processing apparatus 1 selects the cell having the cell identification information “23”. The value “0” assigned to is recorded as a side element spare value.

  The image processing apparatus 1 obtains a value represented by the sum of the side element preliminary values recorded in this process and the preliminary values (i = 1, 2,..., N−1) of the i-th block. Here, since the spare side element value is “0”, the spare value of the first block is “6”, and the spare value of the second block is “9”, the image processing apparatus 1 uses the cell identification information “24”. And the vertex identification information of the vertex in “side 0” is “15” which is the sum of these. The image processing apparatus 1 obtains the vertex identification information for each of the temporary identification information by the method described above.

  The image processing apparatus 1 further acquires vertex identification information of each vertex of the polygon for each polygon identified by the recorded polygon identification information. This processing may be executed by a conventional histogram pyramid method. Then, the image processing apparatus 1 executes drawing processing of each polygon by the same method as before.

  In addition, when the image processing apparatus 1 receives an instruction for moving the vertex or deleting the vertex together with the vertex identification information for specifying the vertex from the user, the image processing apparatus 1 stores the vertex in the virtual space identified by the vertex identification information. The position coordinate is moved according to the instruction, or the vertex is deleted, and the polygon including the vertex is deleted.

  FIG. 8 shows a comparison between the conventional example and the present embodiment in the process of deleting vertices. According to the conventional marching cube method, the vertex A of the cell 1 shown in FIG. 8A (the cell of the cell identification information “1” is abbreviated as cell 1 etc. in the figure) and the vertex of the cell 2 Although A ′ is provided with information for identifying a vertex for each cell even though it is in the same position, the vertex A of cell 1 and the vertex A ′ of cell 2 are distinguished from each other. Information is set.

  When the user gives an instruction to delete the vertex A of the cell 1, the conventional image processing apparatus deletes the polygon including the vertex A in the cell 1, but deletes the polygon including the vertex A ′ in the cell 2. do not do. For this reason, it is not as intended by the user to delete the vertex at the position of the vertex A, and in order to operate this as intended by the user, it is at the same position as the vertex A to be deleted. A process of searching for vertices is required, resulting in a time consuming process such as deformation.

  On the other hand, according to the method of the present embodiment, the vertex A of the cell 1 and the vertex A of the cell 2 are both expressed abstractly as points on the side element “0” of the cell 1, and then the vertex identification information Since it is converted to (A), common vertex identification information “A” is given.

  For this reason, when the user gives an instruction to delete the vertex A of the cell 1, the polygon having the vertex A in the cell 2 is also deleted (FIG. 8B), and processing as intended by the user is possible. It becomes. Further, since the polygon to be deleted can be specified by one vertex identification information, the processing load is reduced.

  In addition, in the method according to the present embodiment, the number of vertex identification information with respect to the number of polygons as a whole does not become enormous (in the conventional method, vertex identification information corresponding to the number of polygons multiplied by the number of vertices is issued. ). Thereby, in the method of the present embodiment, the processing load such as drawing is also reduced.

  Specifically, the conventional general calculation process (VTK) using a marching cube (not using the histogram pyramid method for associating vertices with polygons) for the number of polygons and the histogram pyramid method for associating vertices with polygons were used. FIG. 9 shows the difference in processing time including the integration time of the vertices of the same coordinates in the calculation processing (HPMC) by the marching cube in this case and the calculation processing (ProposedMC) by the method of the present embodiment.

  As illustrated in FIG. 9, in the range where the number of polygons is relatively large, the method according to the present embodiment can achieve a speed increase of 5 times or more (over 4 times the overall average) with respect to VTK. In addition, a speedup of three times or more (over three times as a whole average) is also achieved with respect to the marching cube method (HPMC) when the histogram pyramid method is used.

DESCRIPTION OF SYMBOLS 1 Image processing apparatus, 11 Control part, 12 Storage part, 13 Operation part, 14 Display part, 15 Interface part, 20 Polygon model generation part, 21 Data reception part, 22 Cell setting part, 23 Edge element setting part, 24 Identification information acquisition unit, 25 polygon model setting unit, 30 drawing processing unit.

Claims (3)

An image processing apparatus for forming a polygon model by dividing a virtual space forming a virtual polygon model into virtual cells of a predetermined polygon shape,
Means for accepting value data distributed in the virtual space to be processed;
Means for determining a value for each position of each vertex of the polygonal shape of the cell based on the value data;
Based on the values corresponding to the positions of the vertices at both ends of each side element, the side identification information for identifying each side element is set using the sides whose positions do not overlap each other among the sides of each cell. Means for identifying the edge identification information of the edge element where the vertex of the polygon passing through the cell is located;
Polygon model generation means for generating information representing the polygon model using the specified edge identification information;
Including
An image processing apparatus in which information of a polygon model expressed using the edge identification information is subjected to predetermined processing including visualization and deformation operations. The image processing apparatus according to claim 1,
The polygon model generation means includes
For each of the cells, means for counting the number of vertices of the polygon on the side element of the cell, and recording the sum of the values obtained by counting for each side element;
Means for recording a sum of the numbers of vertices of polygons on the side elements of cells belonging to the first-stage block, with a group of a plurality of cells adjacent to each other as a first-stage block;
A group of a plurality of (i−1) -th stages (i is an integer of i> 1) adjacent to each other is defined as an i-th block, and polygons on the side elements in the cells belonging to the i-th block are represented. Means for recording the sum of the number of vertices,
The sum of the number of vertices of polygons on the side elements in the cell belonging to the block in the recorded block unit, or the sum of the number of vertices of polygons on the side elements in the cell in the recorded cell unit An image processing apparatus that generates information for identifying the position of the vertex of each polygon from information representing the polygon model with reference to a value. Computer
Means for accepting value data distributed in the virtual space to be processed;
Means for dividing the virtual space into virtual cells of a predetermined polygonal shape, and determining a value for each vertex position of the polygonal shape of the cell based on the value data;
Based on the values corresponding to the positions of the vertices at both ends of each side element, the side identification information for identifying each side element is set using the sides whose positions do not overlap each other among the sides of each cell. Means for identifying the edge identification information of the edge element where the vertex of the polygon passing through the cell is located;
Polygon model generation means for generating information representing the polygon model using the specified edge identification information;
Function as
A program for providing information of a polygon model represented by using the edge identification information to a predetermined process including visualization and deformation operations.

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