A method for extracting and reconstructing building element outlines in a CAD base map

Abstract

The application discloses a method for extracting and reconstructing building graph element contour in CAD base drawing. The method comprises the following steps: identifying the CAD base drawing, and obtaining a building graph element set, wherein the building graph element set comprises a column line set, a wall line set and a window line set, and elements in the building graph element set are line segments; processing the building graph element set to be converted into an outer contour line; reconstructing the outer contour line in the form of a closed polyline; and storing the outer contour line in different layers in a classified manner. Through the method, the problem of errors in exported drawing lines in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of graphic design technology, and more particularly to a method for extracting and reconstructing the outlines of architectural elements in a CAD base drawing. Background Technology

[0002] Currently, in the field of architectural engineering design, the proportion of 2D design using traditional CAD software remains very high. Collaboration between different design disciplines typically involves appropriately processing the conditional drawings from other disciplines and using them as base maps for reference before designing the content specific to one's own discipline.

[0003] To ensure that downstream design professionals can view the design drawings in other environments, it is necessary to export them as highly compatible T3 drawing files. In this exported T3 drawing, custom entity elements are broken down into basic lines, blocks, and text in CAD, losing their custom entity attributes. Some of these elements are interactive elements for downstream professionals during the design process (e.g., walls, columns, windows). Therefore, downstream professionals often need to piece these scattered elements together and extract them into their own design drawings for subsequent design and comparison. For example, placing fire hydrants requires consideration of walls and columns as the basis for defining the fire protection zone, and checking fire protection coverage also requires excluding obstructions from walls and columns.

[0004] The current conventional method for extracting and restoring the outer contour of scattered lines in a t3 file is as follows: start searching from any line of the element to be extracted in the base map, obtain other lines connected to the start and end points of the given line, then traverse and connect them, and finally reconstruct the outer contour in the current design drawing.

[0005] Due to the imperfections in the export function of secondary development design software, exported drawings often suffer from problems such as missing lines, misalignment, overlap, breaks, and isolated lines. Existing technologies using traversal connection methods cannot effectively handle these special cases. For example, they may prematurely stop traversing when encountering broken lines or repeatedly loop when encountering overlapping lines, resulting in the inability to form the required closed loop of lines and to correctly extract and connect all the lines that need to be generated.

[0006] There is currently no effective solution to the aforementioned problems in the relevant technologies. Summary of the Invention

[0007] The main objective of this application is to provide a method for extracting and reconstructing the outlines of architectural elements in CAD base drawings, so as to at least solve the problem of errors in the lines exported from drawings in related technologies.

[0008] To achieve the above objectives, according to one aspect of this application, a method for extracting and reconstructing architectural element outlines from a CAD base drawing is provided. The method includes: identifying the CAD base drawing and obtaining a set of architectural elements, wherein the set of architectural elements includes a set of column lines, a set of wall lines, and a set of window lines, and the elements in the set of architectural elements are line segments; processing the set of architectural elements into outer contour lines; reconstructing the outer contour lines in the form of closed polylines; and classifying and storing the outer contour lines into different layers.

[0009] Optionally, traverse all line segments and keep only one of the same type of line segment. The same type of line segment includes line segments that have the same start and end points as other line segments and line segments that have the opposite start and end points to other line segments.

[0010] Optionally, identify and repair line segments that affect the closure of the column outline; create buffer rectangular bounding boxes for each line segment, with the buffer length of the buffer rectangular bounding box being a preset tolerance precision; then take the union of all buffer rectangular bounding boxes to obtain a double-buffered polygon; perform reverse offset processing on the double-buffered polygon according to the preset tolerance precision and remove duplicates to obtain the outer contour lines that are connected to each other.

[0011] Optionally, construct a set of line segment start points and a set of line segment end points. Each node corresponds to a set of line segments connected to the node, where the node is either the start point or the end point of the line segment. Obtain nodes with only one line segment and denote them as single-line nodes and single lines. Obtain the line segment closest to the single-line node as line segment number two. If line segment number two is parallel to the single line, draw a perpendicular line from the single-line node to line segment number two as line segment number three. When the length of line segment number three is greater than the preset tolerance accuracy, add line segment number three to the architectural element set according to the category. If line segment number two is not parallel to the single line, obtain the intersection point of line segment number two and the single line, and adjust the coordinate values ​​of the node closest to the intersection point between line segment number two and the single line to be the same as the intersection point.

[0012] Optionally, starting from the beginning of the line segment, rotate counterclockwise by 135° along the positive direction of the line segment and move the starting point by sin(45°)*2 times with a preset precision to obtain the first enclosing point; starting from the beginning of the line segment, rotate counterclockwise by 225° along the positive direction of the line segment and move the starting point by sin(45°)*2 times with a preset precision to obtain the second enclosing point; starting from the beginning of the line segment, rotate counterclockwise by 315° along the positive direction of the line segment and move the starting point by sin(45°)*2 times with a preset precision to obtain the third enclosing point; starting from the beginning of the line segment, rotate counterclockwise by 45° along the positive direction of the line segment and move the starting point by sin(45°)*2 times with a preset precision to obtain the fourth enclosing point; connect the first enclosing point, the second enclosing point, the third enclosing point, and the fourth enclosing point respectively to obtain a closed contour line.

[0013] Optionally, each edge of the double-buffered polygon is offset by a distance with a preset tolerance precision along the specified normal direction, and adjacent offset segments are connected to form a new polygon. The intersection point is obtained by using the CAD default miter connection method. Multiple closed polyline contours are converted into regions using CAD, and Boolean union operation is performed to merge multiple regions. The merged regions are then converted into closed polylines through block decomposition to obtain the outer contour line.

[0014] Optionally, when processing window lines, extract the start and end coordinates of all window line segments, find the minimum and maximum point coordinates, construct the window rectangle outline using the minimum and maximum point coordinates, and store the line segments of all window rectangle outlines into the window line set.

[0015] Optionally, the wall line portion inserted into the column outline is trimmed; when the wall line intersects with the window line or column line, the wall line is cut and split according to the starting and ending coordinates of the wall line, and the node coordinates are adjusted so that the node belongs to the wall line and the window line or column line that intersects with the wall line.

[0016] This application employs the following steps: identifying the CAD base map and obtaining a set of architectural elements, which includes a set of column lines, a set of wall lines, and a set of window lines, with the elements in the set being line segments; processing the set of architectural elements to convert it into an outer contour line; reconstructing the outer contour line in the form of a closed polyline; and classifying and storing the outer contour line into different layers. This solves the problem of errors in exported drawing lines in related technologies, thereby avoiding special cases such as broken lines, overlaps, and intersections, and correctly connecting the contour lines. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating a method for extracting and reconstructing the outline of architectural elements in a CAD base map, according to an embodiment of this application.

[0019] Figure 2 This is a schematic diagram of the single-line buffer outline;

[0020] Figure 3 It uses a buffer zone to construct a schematic diagram of the column outline;

[0021] Figure 4 This is a schematic diagram of the buffered polygon reverse offset method;

[0022] Figure 5 This is a schematic diagram illustrating the steps for extracting the form outline. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0027] This embodiment provides a method for extracting and reconstructing architectural element outlines in a CAD base drawing, which runs on a mobile terminal, computer terminal, or similar computing device. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0028] Figure 1 This is a flowchart illustrating a method for extracting and reconstructing architectural element outlines from a CAD base drawing, according to an embodiment of this application. Figure 1 As shown, the method includes the following steps:

[0029] Step S101: Identify the CAD base map and obtain the architectural element set, which includes a column line set, a wall line set, and a window line set. The elements in the architectural element set are line segments.

[0030] Specifically, in architectural base drawings, elements such as walls, columns, and windows are typically located in layers with different names, thus allowing for categorization by layer name. In practice, the user is first prompted to select architectural base drawing block references in the current drawing space. Then, using the filter functions provided by the CAD API, the corresponding elements are selected by element category "Line" and layer name. Since elements in architectural base drawings may also contain nested blocks, it is necessary to traverse all nested block references and use appropriate coordinate transformation functions to convert the coordinates of the architectural elements in these block references to the coordinate system of the current model space. For ease of explanation later, the extracted architectural element sets are defined as column line sets, wall line sets, and window line sets, respectively. The outer contour of architectural elements is represented by closed polylines.

[0031] Step S102: Process the set of architectural elements into an outer contour line;

[0032] Step S103: Reconstruct the outer contour lines as closed polylines, and classify and store the outer contour lines into different layers.

[0033] Specifically, the outer contours of the processed architectural elements are reconstructed as closed polylines, ensuring that the outer contours do not have any gaps or breaks. Finally, the contours are categorized and stored in different layers.

[0034] In one alternative embodiment, all line segments are traversed, and only one line segment of the same type is retained. The line segments of the same type include line segments that have the same start and end points as other line segments and line segments that have the opposite start and end points to other line segments.

[0035] Specifically, the line segments in the bar set are deduplicated to remove overlapping bars. The checking method is to traverse all bar segments. If there are several bars with the same starting point and the same ending point, or whose starting point and ending point are opposite, since the line segments of these bars completely overlap, the extra ones are removed, and only one is kept.

[0036] In one optional embodiment, line segments that affect the closure of the column contour are identified and repaired; buffer rectangular bounding boxes are created for each line segment, with the buffer length of the buffer rectangular bounding box being a preset tolerance precision; then, the union of all buffer rectangular bounding boxes is taken to obtain a double-buffered polygon; the double-buffered polygon is reverse-offset according to the preset tolerance precision and deduplicated to obtain the outer contour lines that are connected to each other.

[0037] Specifically, the line segments in the column set are deduplicated, and missing lines with excessive length that affect the closure of the column outline are identified and repaired. A buffer rectangular bounding box is created for each line segment in the column set, with a buffer length set to a preset tolerance. These buffer bounding boxes are then joined together to obtain a double-buffered polygon of the column outline. Finally, the double-buffered polygon is reverse-offset according to the preset tolerance and deduplicated, thus degenerating to obtain the outer outline of the interconnected columns.

[0038] In one optional embodiment, a set of line segment start points and a set of line segment end points are constructed. Each node corresponds to a set of line segments connected to the node, where the node is either the start point or the end point of a line segment. Nodes with only one line segment are identified and denoted as single-line nodes and single lines. The line segment closest to the single-line node is identified as line segment number two. If line segment number two is parallel to the single line, a perpendicular line is drawn from the single-line node to line segment number two as line segment number three. When the length of line segment number three is greater than a preset tolerance accuracy, line segment number three is added to the architectural element set according to the classification. If line segment number two is not parallel to the single line, the intersection point of line segment number two and the single line is identified, and the coordinate values ​​of the node closest to the intersection point between line segment number two and the single line are adjusted to be the same as the intersection point.

[0039] Specifically, identify and repair missing lines that are too long and affect the closure of the column outline. The checking method is to determine whether any column has connected columns at its start and end points. First, construct the node sets for the start and end points of the column, and each node contains a set of connected line segments. Then, traverse all nodes and check if there is only one line segment connected to a certain node P1. If so, mark the line segment as L1. Then, take the other line segment L2 that is closest to node P1. If L2 is parallel to L1, construct a new line segment L3. If its length is greater than twice the preset tolerance accuracy (e.g., 1mm), add it to the column set. The starting point of this line segment is node P1, and the ending point is the foot of the perpendicular from P1 to L2. If L2 is not parallel to L1, calculate the intersection point P2 of the two line segments, and adjust the coordinates of the node closest to the intersection point P2 in L1 and L2 to P2.

[0040] In an alternative embodiment, reference is made to Figure 2And 3, starting from the beginning of the line segment, rotate counterclockwise by 135° along the positive direction of the line segment, and move the starting point according to the preset precision sin(45°)*2 times to obtain the first enclosing point; starting from the beginning of the line segment, rotate counterclockwise by 225° along the positive direction of the line segment, and move the starting point according to the preset precision sin(45°)*2 times to obtain the second enclosing point; starting from the beginning of the line segment, rotate counterclockwise by 315° along the positive direction of the line segment, and move the starting point according to the preset precision sin(45°)*2 times to obtain the third enclosing point; starting from the beginning of the line segment, rotate counterclockwise by 45° along the positive direction of the line segment, and move the starting point according to the preset precision sin(45°)*2 times to obtain the fourth enclosing point; connect the first enclosing point, the second enclosing point, the third enclosing point, and the fourth enclosing point respectively to obtain a closed contour line.

[0041] In one optional embodiment, each edge of the double-buffered polygon is offset by a distance with a preset tolerance accuracy along the specified normal direction, and adjacent offset segments are connected to form a new polygon. The intersection point is obtained by using the CAD default miter connection method. Multiple closed polyline contours are converted into regions using CAD, and Boolean union operation is performed to merge multiple regions. The merged regions are then converted into closed polylines through block decomposition to obtain the outer contour line.

[0042] Specifically, the advantage is that it can simultaneously merge overlapping lines and broken lines within the tolerance range into the same area. In this way, when area degradation is performed, the center line segment will be automatically reconstructed to achieve the effect of line segment continuation.

[0043] Alternatively, refer to Figure 4 The method for reverse offsetting the buffered polygon is to first offset each edge of the polygon by a distance with a specified tolerance accuracy along the normal direction, and then connect adjacent offset segments to form a new polygon. The intersection point is obtained by using the CAD default miter connection method, so that there will be no arc segments.

[0044] In one alternative embodiment, when processing window lines, the start and end coordinates of all window line segments are extracted, the minimum and maximum point coordinates are found, and the window rectangular outline is constructed using the minimum and maximum point coordinates. All window rectangular outline line segments are stored in the window line set.

[0045] Specifically, refer to Figure 5The method for extracting window outlines is basically the same as for column lines. Due to the special appearance of windows in plan view, there are usually extra lines representing window sashes inside the outline, so these lines need to be excluded when extracting the outline. The operation method is as follows: first, obtain the block reference of each window one by one; second, extract the start and end coordinates of all window line segments in its block definition; find the coordinates of the minimum and maximum points respectively; then, use these two coordinate points to construct the window rectangle outline of the current nested level; finally, transform the offset vector of each nested block reference to construct the final window rectangle outline.

[0046] In one alternative embodiment, the wall line portion inserted into the column outline is trimmed; when the wall line intersects with the window line or column line, the wall line is cut and split according to the starting coordinates and ending coordinates of the wall line, and the node coordinates are adjusted so that the node belongs to the wall line and the window line or column line that intersects with the wall line.

[0047] Specifically, extracting the wall outline is similar to extracting the column outline, but requires additional processing compared to extracting columns and windows. First, the wall lines inserted inside the column outline must be trimmed to ensure the wall outline does not intersect with the column outline. Second, if the wall outline is connected to a column (window), the coordinates of the connection points must be adjusted to ensure the connecting node coordinates belong to both the wall and the column (window). To ensure that adjusting the node coordinates does not cause other wall line segments to break or intersect, the wall lines need to be cut and split according to their start and end point coordinates before adjusting the coordinates, ensuring that no wall line segment has an endpoint in the middle.

[0048] This invention extracts graphic element outlines by establishing a rectangular bounding box for line segment buffers, which minimizes the risk of broken lines, overlaps, intersections, and other special cases that prevent proper connection and closure of outlines. The extraction process employs customized methods based on the type of graphic element being extracted; for example, internal lines are excluded when extracting window outlines, and proper connections to columns and windows are ensured when extracting wall outlines.

[0049] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0050] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0051] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0052] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0053] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0054] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0055] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0056] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0057] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method of extracting and reconstructing building feature outlines in a CAD base map, characterized by, include: Identify the CAD base map and obtain the architectural element set, wherein the architectural element set includes a column line set, a wall line set, and a window line set, and the elements in the architectural element set are line segments; The architectural element set is processed and converted into an outer contour line; The process of converting the set of architectural elements into an outer contour line includes: identifying and repairing line segments that affect the closure of the column contour; establishing buffer rectangular bounding boxes for each line segment, wherein the buffer length of the buffer rectangular bounding box is a preset tolerance precision; then taking the union of all the buffer rectangular bounding boxes to obtain a double-buffered polygon; and performing reverse offset processing on the double-buffered polygon according to the preset tolerance precision and removing duplicates to obtain an outer contour line that is connected to each other. Identifying and repairing line segments that affect the closure of column outlines includes: constructing a set of line segment start points and a set of line segment end points, where each node corresponds to a set of line segments connected to the node, and the node is either the start point or the end point of a line segment; obtaining nodes with only one line segment and labeling them as single-line nodes and single lines, and identifying the line segment closest to the single-line node as line segment number two; if line segment number two is parallel to the single line, drawing a perpendicular line from the single-line node to line segment number two as line segment number three, and adding line segment number three to the architectural element set according to its classification when the length of line segment number three is greater than a preset tolerance accuracy; if line segment number two is not parallel to the single line, obtaining the intersection point of line segment number two and the single line, and adjusting the coordinate values ​​of the node closest to the intersection point between line segment number two and the single line to be the same as the intersection point; The outer contour lines are reconstructed in the form of closed polylines, and the outer contour lines are categorized and stored in different layers.

2. The method according to claim 1, characterized in that, The process of converting the set of architectural elements into an outer contour line includes: Traverse all line segments and keep only one of each type of line segment. The type of line segment includes line segments that have the same start and end points as other line segments and line segments that have the opposite start and end points to other line segments.

3. The method according to claim 1, characterized in that, For each line segment, a buffer rectangle is created, with the buffer length of the buffer rectangle being a preset tolerance precision. Then, the union of all the buffer rectangles is taken to obtain a double-buffered polygon, including: Rotate 135° counterclockwise from the starting point of the line segment along the positive direction of the line segment, and move the starting point according to a preset precision of sin(45°)*2 times to obtain the first enclosing point; Rotate 225° counterclockwise from the starting point of the line segment along the positive direction of the line segment, and move the starting point according to a preset precision of sin(45°)*2 times to obtain the second enclosing point; Rotate 315° counterclockwise from the starting point of the line segment along the positive direction of the line segment, and move the starting point according to the preset precision sin(45°)*2 times to obtain the third enclosing point; Rotate 45° counterclockwise from the starting point of the line segment along the positive direction of the line segment, and move the starting point according to the preset precision sin(45°)*2 times to obtain the fourth enclosing point; Connect the first enclosing point, the second enclosing point, the third enclosing point, and the fourth enclosing point respectively to obtain a closed contour line.

4. The method according to claim 1, characterized in that, The double-buffered polygons are reverse-offset according to a preset tolerance accuracy and deduplicated to obtain interconnected outer contour lines, including: Offset each edge of the double-buffered polygon by a distance with a preset tolerance accuracy along the specified normal direction, connect adjacent offset line segments to form a new polygon, and obtain the intersection point using the CAD default mitered connection method; Multiple closed polyline contours are converted into regions using CAD, and Boolean union operation is performed to merge the multiple regions. The merged regions are then converted into closed polylines through block decomposition to obtain the outer contour line.

5. The method according to claim 1, characterized in that, Before processing the set of architectural elements into an outer contour line, the process includes: When processing the window lines, extract the start and end coordinates of all window line segments, find the minimum and maximum point coordinates, construct the window rectangle outline using the minimum and maximum point coordinates, and store all the line segments of the window rectangle outline into the window line set.

6. The method according to claim 1, characterized in that, Before processing the set of architectural elements into an outer contour line, the following steps are included: Trim off the portion of the wall trim that is inserted inside the column outline; When a wall line intersects with a window line or column line, the wall line is cut and split according to the starting and ending coordinates of the wall line, and the node coordinates are adjusted so that the node belongs to the wall line and the window line or column line that intersects with the wall line.

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