CN102034268A - Method for constructing and storing three-dimensional virtual plant based on dynamic substructure - Google Patents

Abstract

The present invention proposes a three-dimensional virtual plant construction and storage method based on dynamic substructure, including substructure parameter initialization, constructing plant structure according to the dynamic substructure method, saving data of the substructure method, and using substructure information to carry out plant structure Interactive editing of structures. The present invention is characterized in that a substructure library is defined for similar substructures in the plant structure, and time and space are saved by repeatedly calling the information therein. The samples in the substructure library can be dynamically generated according to the needs, so as to avoid that the generated substructures are not called. Compressed storage of virtual plant data can be achieved by keeping only one copy of repeatedly called substructures. According to the call information of the substructure, the constructed plants and plant substructures can be interactively edited.

Description

A 3D virtual plant construction and storage method based on dynamic substructure

technical field

The invention belongs to the technical fields of virtual reality, digital agriculture and forestry, digital entertainment, landscape design, etc., and in particular relates to a modeling method and dynamic display of virtual plant structures.

Background technique

With the development of three-dimensional display technology, the demand for display content in the digital environment is rapidly increasing. As an important part of nature, plants are an essential part of digital scene construction for their modeling and animation. The main methods of constructing and realizing the three-dimensional structure of virtual plants can be roughly divided into two categories. One is the manual interaction method, that is, the structure of virtual plants is defined by applying professional design software. Simple plant structures or plant organs can be modeled manually in an interactive manner, but for complex plant structures, which may contain millions of organs, it is not feasible to model them entirely by hand. Another type of modeling is algorithm-based simulation, which automatically generates plant structures. Common simulation algorithms include string replacement systems, particle systems, automata, etc.

When using algorithms to simulate plant structures, the common feature is to define growth rules, describe the types of branches produced by different terminal buds or lateral buds, and even the types and numbers of organs included. The intuitive simulation method is to traverse all plant structures in a certain order in each iteration, and update the state of branches one by one. If the number of simulated plants is large and the plant structure is complex, the traversal of the plant structure will consume a lot of computing time, making it difficult to debug and apply the results.

In fact, complex plant structures often contain a large number of similar branches, more often in mature trees. According to the observation of the plants, the branches of the whole ground plants can be divided into a limited number of categories. Plant botanists believe that branching types can be classified by physiological age. Similar characteristics of plant branches can be used for rapid construction of plant structures. Each type of branch can be called a substructure, and each substructure can be decomposed into a growth axis and the substructure of the next layer until the substructure of the next layer is no longer included. For a single plant, the top substructure is the plant itself. The substructure construction method is to define a substructure library for each type of substructure; the plant structure construction process starts from the simplest substructure, and proceeds layer by layer from top to bottom through substructure calling and geometric transformation. In this algorithm, the calculation time is proportional to the size of the substructure library, rather than proportional to the number of organs in the plant structure, which has obvious advantages for complex plant structures. It is proved by experiments that for complex plant structures, the efficiency of this algorithm is higher than that of the traversal algorithm of plant structures. However, in the past such methods, the substructure library was constructed at one time from simple to complex, top-down order, which is not only unintuitive, but also wastes resources because some substructures are not called. For simple plant structures , the simulation time is higher than that of the traversal algorithm.

At present, there are several commercial software dedicated to building virtual plant structures in the world, such as xfrog, Onxy tree, Speed tree, AMAP, etc., most of which provide plug-ins for mainstream software for desktop design. There is no such professional software in China. The present invention can be used in the algorithm design of such software.

Contents of the invention

The technical problem to be solved by the present invention is how to efficiently and flexibly utilize the similarity of plant branches while retaining the advantages of the plant structure traversal algorithm to construct, save, call, interactive edit and compress storage of virtual plants. To this end, a method of constructing and storing 3D virtual plants based on dynamic substructure is proposed.

In order to realize the object of the present invention, the steps of the three-dimensional virtual plant construction and storage method based on the dynamic substructure of the present invention are as follows:

Step S1: Initialize the substructure parameters, determine the type of branches in the virtual plant, that is, the substructure, and the layer-by-layer calling relationship; specify the maximum number of substructures in each layer, that is, the size of the substructure library;

Step S2: Construct the plant structure according to the dynamic substructure method. First, construct the growth axis of the virtual plant. For any substructure position on the growth axis of the virtual plant, if the corresponding substructure already exists in the substructure library, directly from the substructure Called in the library, perform geometric transformation and combine into the current substructure; otherwise, recursively build the substructure layer by layer, put it into the corresponding substructure library, until the virtual plant structure is constructed;

Step S3: Save the plant data in the substructure method; for each type of substructure, the plant data is the information of the plant growth axis created in the simulation process, and the substructure number and transformation matrix at the position of the substructure;

Step S4: Use substructure information to interactively edit the plant structure; the calling relationship between substructures can be obtained from step S3 or step S2.

Among them, a substructure library is defined for similar substructures in the plant structure, and time and space are saved by repeatedly calling the information in it.

Wherein, the samples in the substructure library can be dynamically generated according to needs, and the generated substructures can be prevented from being called.

Among them, the compressed storage of the virtual plant can be achieved by saving only one backup of the repeatedly called substructure, and the constructed plant and the plant substructure can be interactively edited according to the calling information of the substructure.

The beneficial effects of the present invention: for the substructures that appear repeatedly in the plant structure, only limited substructure samples need to be simulated, and the simulation efficiency is improved by reusing the information of the substructure samples. Note that substructure is a recursive concept. The virtual plant can be decomposed into the main axis and the substructure directly growing on the main axis, and the substructure on the main axis can be divided into the growth axis and the substructure of the next layer. The virtual plants themselves are substructures in the forest scene. Since the substructure in this method is dynamically created according to the needs during the construction of the plant structure, there is no waste of time and space caused by the substructure not being called, and the simulation efficiency can be guaranteed to be higher than that of the plant structure of different complexity. Algorithm for complete traversal of plant structures. Users can vary the substructure size to achieve desired efficiency and substructure diversity. The plant construction process is carried out from the bottom up, and it is more intuitive to traverse the dynamically created substructure. Usually, the space occupied by the file that saves the virtual plant geometry increases linearly with the number of organs; for the plant structure constructed by applying the dynamic substructure algorithm, since the information of the substructure is reused, only the transformation and calling information of the substructure need to be saved , so as to achieve the purpose of saving space. When reading such a file, it takes a certain amount of time to unravel and change the substructure layer by layer, so this is a method of exchanging time for space. Plants can be manipulated interactively since the substructure call information is saved.

Description of drawings

Figure 1a is a framework diagram of the dynamic substructure-based approach.

Fig. 1b is a sub-flow chart of step S2 in Fig. 1a.

Fig. 2 is a schematic diagram of simulation and calling based on random substructure.

Figure 3 is an example of substructures of different categories included in the plant structure.

Figure 4a and Figure 4b are schematic diagrams of the construction of the substructure method of the forest scene.

Figure 5 is the simulation result of the complex plant structure in Qingyuan software.

Figure 6 is the simulation result of random plant structure in Qingyuan software.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in combination with specific implementation examples and with reference to the accompanying drawings. It is assumed that the reader is familiar with plant structure simulation algorithms, such as automata, string replacement systems, etc., and focuses on how to apply dynamic substructure algorithms in such algorithms.

Figure 1a shows the relationship of the various parts implementing the dynamic substructure approach.

Step S1 initializes the parameters of the plant structure, and determines the type of branches or substructures in the virtual plant and the layer-by-layer call relationship; the maximum number of substructures in each layer is given, that is, the size of the substructure library; to achieve the expected virtual plant Structure, first decompose the plant structure, determine the substructure types contained in it and the layer-by-layer combination relationship; the division of substructure types can refer to the physiological age proposed by botanists. Each type of substructure adopts the same plant structure simulation parameters.

Step S2 constructs the plant structure according to the dynamic substructure method, and the specific process is shown in Figure 1b. Since the substructure is a recursive concept, for the convenience of description, the substructure currently being constructed is called the current substructure, and the substructure on the growth axis of the current substructure is called the next substructure. The substructure of the current substructure relative to the next layer is called the previous substructure. The category of the current substructure is represented by an integer p, and p=0 represents the virtual plant itself. The category of the next substructure contained in the current substructure is represented by an integer q, and generally q is greater than p. The size of the substructure library corresponding to substructure p is T _p , and the size of the substructure library corresponding to substructure q is T _q , both of which are defined in step S1. The simulation process starts with the main axis of the plant (p=0).

Step 21: Construct the growth axis of the current substructure numbered n _p according to the plant structure simulation algorithm, and store it in the substructure library corresponding to the substructure p, n _p ∈ [1, T _p ];

Step 22: In a certain order, traverse all the positions on the growth axis of the current substructure numbered _np to generate the next layer of substructures. According to the plant structure simulation algorithm, the category q, position and direction of the next substructure on the growth axis of the current substructure with number n _p are obtained.

Step 23: Determine whether the traversal has ended, and whether the information of the substructure of the next level has been included in the current substructure; if the traversal has not ended, and there is still a vacant position in the next level of substructure, go to step 24, if the traversal has ended , go to step 27.

Step 24: Generate an integer substructure number m q between 1 and T _q according to the next substructure category q on the growth axis of the current substructure with number n _p , _{m q ∈} [1, T _q ].

Step 25: Determine whether the numbered substructure m _q has been constructed before and exists in the substructure library corresponding to category q. If it exists, go to step 21, and recursively build the next substructure numbered m _q in the same process as the current substructure n _p ; at this time, the substructure numbered m _q becomes the current substructure. If the substructure m _q of the next level already exists in the substructure library corresponding to the substructure q, go to step 26 .

Step 26: According to the position and direction of the substructure m _q of the next layer, perform geometric transformation and combine it into the current growth axis, do not repeat the construction, and go to step 22 after completion.

Step 27: If all the substructures on the current growth axis have been constructed, the construction of the current substructure is completed, and the next layer of substructure is transferred to the top-level structure.

Fig. 2 is a schematic diagram of simulation and calling based on random substructure, showing the process of constructing plant structure by dynamic substructure method. Among them, the black dotted arrow is the simulation order of the substructure, and the green curved arrow is the return order of the substructure. S ₁ represents the virtual plant to be constructed, and the blue axis is its growth axis. The size of the substructure library at all levels is 5. When constructing the substructure in the ellipse, first judge whether the substructure exists in the substructure library corresponding to _S2 , if not, enter the substructure sample construction at the level of _S2 : Simulation S ₂ The growth axis of the substructure sample in the substructure library, traverse all the substructure positions, and judge whether a substructure with a certain number exists. If it does not exist, go to the next layer for construction. This continues until the simplest level of substructure S ₄ . Then call and return layer by layer.

Step S3 represents the storage of plant data in the substructure method; for each type of substructure, the plant data is the information of the growth axis of the plant created during the simulation process, as well as the substructure number and transformation matrix at the position of the substructure. When there are a large number of repeated substructure calls, only one backup is saved for the repeated substructure data. Data saving can be carried out synchronously with the plant structure construction process of step S2, or it can be realized after step S2 is completed. Plant organs can be seen as a special case of substructures, whose geometry is defined separately. Each organ corresponds to an organ description file, which contains information such as the geometric model and texture coordinates of the organ, and can be manually created by professional software. Only one identifier of the organ is saved in the plant data saved in the substructure, thus saving space. The basic data structure describing a substructure is as follows:

SUBSTRUCTURE

{

int ID; //Identification of the substructure;

int length; //Number of organs included;

ORGAN O(length);//List of organs included

}

Among them, ID is the feature of the substructure, indicating the category of the substructure. length is the number of organs contained in the growth axis, including common organs, such as internodes, leaves, fruits, etc., as well as the substructures therein. O(length) is a specific description of each organ. The description of its data structure ORGAN is as follows:

ORGAN

{

int symbol; //organ category;

int ID; //organ identification;

float Mo(3,4); //geometric transformation matrix;

float So(2); //Organ size for organs, meaningless for substructures.

int num_sons; //The number of organs pointed to

int id_sons(num_sons); //The sub-organ identification pointed to

int id_parent; //parent organ identification

}

Among them, symbol is used to identify the organ or substructure stored in the data structure ORGAN, and different organs have different categories, corresponding to the organ description file. ID is the characteristic of the organ. Mo contains the rotation and translation transformation matrices of organs or substructures. If symbol indicates that the current substructure is an organ, So is the size of the organ, otherwise it is meaningless. num_sons indicates the number of sub-organs of the current organ. For internodes, the organs and substructures attached to them and the internodes at their tops are considered as suborgans. id_sons(num_sons) stores the identifiers of all sub-organs. Similarly, id_parent stores the identifier of the parent organ of the current organ. All organ or substructure data are stored in standard orientation and size, and its size, orientation and position on the growth axis are given when called.

For the data saved in substructure, the complete plant geometric information can be parsed recursively for subsequent processing. The parsing process described in pseudocode is as follows:

Read_Substructure(SUBSTRUCTURE s)

{

for i=1 to s.length

if O(i).symbol<>'substructure'

Output_Substructure(O(i));//Output organ information

else

Read_Substructure(O(i));

end

end

}

Among them, the function Read_substructure reads the organ information contained in the current substructure one by one, and if the organ is a substructure, further parses the substructure therein. If the organ is an ordinary organ (ie s.symbol<>'substructure'), then directly read the information of the organ description file, transform it according to the transformation matrix Mo and return it. Since the ID of each substructure is unique, the substructure can be directly accessed through the ID, so that the substructure information at any position can be obtained. For example, Figure 3 is an example of substructures of different categories included in the plant structure, and from left to right are substructures of different categories with containment relationships.

Step S4 uses the substructure information to interactively edit the plant structure. For example, the user performs operations such as branch pruning and dragging. In the process of interaction, the call relationship between the substructures is required, so that after the user selects a certain position on the growth axis of a substructure on the screen, all the plant components above the position can be selected. The calling relationship between substructures can be obtained from step S3, or from step S2, the latter means interactive editing during the simulation process. After selection, actions such as pruning, leaf thinning, and dragging can be performed. The above operation is equivalent to creating a new substructure. At this time, it is necessary to modify the connection relationship between the substructures, save the number of the new substructure in the upper substructure, and reduce the number of times the old substructure is called. The modified information is sent back to step S2 or step S3.

The above idea of plant structure construction based on dynamic substructure can be extended to the construction of plant communities, that is, as shown in Figure 4a and Figure 4b, a schematic diagram of the construction method of the substructure of the forest scene is shown. When constructing a scene containing a large number of plant individuals, only limited simulation several plant samples from the phylogenetic population, and then build communities by reusing this information. Fig. 4a shows a virtual plant sample, and Fig. 4b shows a plant scene constructed by repeatedly applying these several samples.

Here we give the implementation results in the "Qingyuan" software. "Green Garden" is a plant growth and structure simulation software based on the GreenLab functional structure model developed by our research group, which can be used to construct various crops and plants. The GreenLab model is a general mathematical model based on the basic assumptions of botany. Qingyuan software has realized the method described in the present invention with c++ language, and carried out the test. The configuration of the PC is Intel Core(TM) 21.86G CPU, 2G memory, and the operating system is Windows XP Professional. Figure 5 shows the simulation results of complex plant structures in Qingyuan software, a simulation of a complex poplar tree based on deterministic substructure, which contains 12.106 million organs, and the model calculation time is 10.2 seconds. Figure 6 is the simulation result of random plant structure in Qingyuan software, which is the simulation of pine trees based on random substructure, where the size of the substructure library is 5. It shows that with such a small substructure size, good visual effects can be obtained.

The above is only a specific implementation mode in the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technology can understand the conceivable transformation or replacement within the technical scope disclosed in the present invention. All should be covered within the scope of protection of the claims of the present invention.

Claims (4)

1. the three-dimensional plant based on dynamic minor structure makes up and storage means, it is characterized in that described method comprises that step is as follows:

Step S1: the minor structure parameter initialization, determine that branch in the virtual plant is the type of minor structure and call relation successively; The maximum number of given every straton structure, i.e. minor structure storehouse size;

Step S2: make up plant structure according to dynamic substructure method, at first make up the growth axis of virtual plant, for the anyon locations of structures on the growth of virtual plant axle, if corresponding minor structure exists in the minor structure storehouse, then directly from the minor structure storehouse, call, carry out being combined to current minor structure after the geometric transformation; Otherwise, recursively successively make up minor structure, put into corresponding minor structure storehouse, finish up to the virtual plant structure construction;

Step S3: the plant data with substructure method are preserved; For each class minor structure, wherein the plant data are the information of the plant growth axis created in simulation process, and locational minor structure numbering of minor structure and transformation matrix;

Step S4: utilize minor structure information that plant structure is carried out interactive editing; Call relation between the minor structure can obtain from step S3, also can obtain from step S2.

2. the three-dimensional plant based on dynamic minor structure according to claim 1 makes up and storage means, it is characterized in that, to minor structure storehouse of minor structure definition similar in the plant structure, saves time and the space by wherein information is repeated to call.

3. the three-dimensional plant based on dynamic minor structure according to claim 1 makes up and storage means, it is characterized in that, the sample evidence in the described minor structure storehouse needs and can dynamically produce, and the minor structure that can avoid producing is not called.

4. the three-dimensional plant based on dynamic minor structure according to claim 1 makes up and storage means, it is characterized in that, can only preserve the compression storage that a backup reaches virtual plant by the minor structure that the counterweight polyphony is used, can carry out interactively editor to plant and plant minor structure after making up according to the recalls information of minor structure.

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