CN101650837A - Virtual-reality modeling method of ocean water body - Google Patents

Abstract

The invention discloses a virtual reality modeling method of ocean water body. Using RS (remote sensing) data through convenient and efficient data processing and scientific storage methods, and using OpenGL technology to build the main body of the model, using the contour line of the sea surface test area to construct a three-dimensional modeling method for the three-dimensional ocean water body, and expressing the sea surface by texture mapping Waves use the "projection" of parallel contour lines to construct water body columns to express the changes in physical quantities such as water depth and water quality in RS data, and reproduce ocean water bodies and seabed topography in a volume-transparent manner. The invention is a new method for realizing three-dimensional ocean water body modeling by using OpenGL as a modeling tool under the technical support of RS and GIS (Geographic Information System). The present invention effectively utilizes long-term accumulated RS data, realizes real-time modeling of three-dimensional ocean water bodies through the above model drawing method through convenient and feasible data processing. The invention has very wide application prospect in the field of marine environment monitoring.

Description

A Virtual Reality Modeling Method for Ocean Water Body

technical field

The invention relates to a modeling method of an ocean water body, in particular to a virtual reality modeling method of an ocean water body. It is used to realize rapid and real-time modeling of marine water bodies. Using this method, the observation area can be arbitrarily delineated in the China Sea area for 3D modeling.

Background technique

The ocean accounts for about 71% of the earth's surface area. It is an open and complex system with diversity, in which there are various time and space scales and different levels of material existence and movement forms. At present, the expression of ocean water bodies is mainly in the form of two-dimensional maps such as electronic charts, and the inversion data such as ocean temperature, salinity, and transparency mostly exist in the form of text. With the development and utilization of marine resources, the demand for 3D modeling and visualization of marine water and marine environment inversion data is gradually increasing. The development and utilization of marine resources should be based on the characteristics and laws of the ocean. The development of computer technology, virtual reality technology and other related technologies has provided strong technical support for 3D modeling of marine water bodies.

The real-time modeling of the virtual reality ocean water body of the present invention is an important means for understanding the comprehensive ocean environment, and is a new method for reproducing related physical quantity indicators such as ocean temperature, salinity, and transparency. The virtual reality modeling method of marine water body based on RS and GIS proposed in this study can realize rapid and real-time modeling of marine water body, and can model the water body of any demarcated area in the China Sea.

With the proposal of "Digital Ocean", research on 3D real-time ocean modeling at home and abroad has become increasingly hot, see [1] Rinehart R, Wright D. Benthic Habitat Classification and 3-DVisualizations [C]. Association of American Geographers Centennial Meeting, American , Samoa, 2004.[2]Alan M, et al.Visually-enabled Geo-collaborationto Support Data Exploration & Decision-making[C].Proceedings of the 21stInternational Cartographic Conference, Durban, South Africa, 2003[3] Shangguanwei, etc. Research on Visual Simulation Technology of Real Marine Environment [J]. Journal of System Simulation. 2006: 18 (Add 2). In addition, commercial software at home and abroad is also continuously launched, such as Vega of MultiGen-Paradigm.Inc. However, the research on marine 3D real-time modeling is still in its infancy. The real-time performance is not high, the data sources are diverse and complex, and the commercial software is expensive. These are the main problems at present.

Virtual reality (Virtual Reality) is to construct a realistic model in the computer to generate a simulated environment with a three-dimensional world effect. It is a high-tech method that uses computers to visualize and interact with complex data. Through the simulated virtual environment, visitors can get the feeling of being on the scene.

The OpenGL (Open Graphics Library) graphics system is a software interface that enables programmers to create interactive programs that use computer graphics techniques to generate realistic images. Computer graphics techniques can be controlled using OpenGL to generate photorealistic graphics. OpenGL includes about 250 functions that users can use to specify objects and operations to create interactive 3D applications.

The OpenGL coordinate system involved in the present invention comprises following three kinds:

The world coordinates are the coordinates used to describe the scene in OpenGL. The Z axis is vertical to the outside of the screen, the X axis is from left to right, and the Y axis is from bottom to top. It is a right-handed Cartesian coordinate system.

Object coordinates are "world coordinates" established with a certain point of the object as the origin. This coordinate system is only applicable to the object and is used to simplify the description of the coordinates of each part of the object. When an object is placed in the scene, the coordinate transformation experienced by each part is the same, and the relative position remains unchanged, so it can be regarded as a whole, which is consistent with human thinking habits.

Eye coordinates are directions in a coordinate system with the viewpoint as the origin and the direction of the line of sight as the positive direction of the Z-axis.

With the development of marine environmental satellite remote sensing, a large amount of RS data has been or is being managed and maintained using GIS technology. The marine environmental satellite remote sensing data has the characteristics of wide range and high real-time performance. Modeling can make a large amount of RS data become one of the most intuitive materials reflecting ocean water bodies.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a virtual reality modeling method for ocean water bodies. The modeling method of ocean water body virtual reality is as follows:

1) Through the data conversion service, the text format of the original marine remote sensing environment inversion data is automatically converted into a raster dataset;

2) The converted data is stored based on time visualization, which supports quick query of the spatio-temporal characteristics of massive remote sensing raster datasets;

3) The spatial coordinate system setting of the OpenGL 3D ocean water scene, after Z-axis scaling, coordinate system translation to the screen along the vertical screen direction, coordinate system rotation, and X, Y-axis coordinate units unified to latitude and longitude coordinates, the scene coordinate system setting is completed;

4) Construct the surface of the three-dimensional ocean water body according to the polygonal contour line of any sea area constructed by the user, and generate the main body of the cube model of the ocean water body by "projecting" parallel contour lines;

5) Use the wave texture of the sea surface to map the sea surface, convert the seabed terrain into OpenGL primitives through the digital elevation model, and use single color rendering and multi-light source parameter settings to model;

6) Obtain the cross-section of the physical quantity of the raster data set by the "projection" of the parallel contour line and the stretching of the terrain simulation, and transparently display the surface of the ocean water body to obtain visualization effects from various angles.

The step of automatically converting the text format of the original marine remote sensing environment inversion data into a raster dataset by means of data conversion services: read the Head file header and data body of the original marine environment inversion data in the form of a file stream Then write it into the raster dataset according to the data organization method of the raster dataset, use the Internet information server to detect the data files in the target folder, and delete the source files after conversion and storage.

The converted data is stored based on time visualization, which supports quick query of the spatio-temporal characteristics of massive remote sensing raster datasets: the storage based on time visualization is the head file of the original marine environment inversion data The product cycle, product generation time period, and product generation time point in the header are respectively stored in the product metadata table, periodic time metadata table, and instantaneous time metadata table, and can be quickly queried with standard SQL time query statements Datasets within a time collection.

The spatial coordinate system setting of the OpenGL three-dimensional ocean water scene, after Z-axis scaling, XY-axis coordinate plane translation to the screen along the vertical screen direction, coordinate system rotation and X, Y-axis coordinate units unified to longitude and latitude coordinates to complete the scene coordinates System setting steps: OpenGL default world coordinate system X-axis, Y-axis and Z-axis coordinate unit length is uniform, but considering the characteristics of ocean water body data, that is, the horizontal direction (X, Y) coordinate range is (180 degrees east longitude to 180 degrees west longitude, 90 degrees north latitude to 90 degrees south latitude), while the depth of the global ocean ranges from 0 meters to more than -10,000 meters, and the coordinate unit lengths of the X-axis, Y-axis direction and Z-axis direction differ by more than 2 times the order of magnitude. It will cause the Z-axis direction to be too steep and the modeling effect will be poor. Therefore, the unit length of the Z-axis coordinate is reduced to 1/100 of the original length, that is, the unit length of the X-axis and Y-axis is 100 on the Z-axis. The world coordinate system of the OpenGL scene and the XY axis plane of the eye coordinate system coincide with the screen plane, so the coordinate system needs to be translated in the screen along the vertical screen direction. The world coordinate system is a right-handed Cartesian coordinate system. The XY axis plane is parallel to the screen. The sea level of the generated scene is parallel to the screen. This is inconsistent with the common sense that the sea level should be in the horizontal direction. Therefore, the coordinate system should be rotated to the Z axis , the positive direction of the X-axis is horizontal to the right, and the positive direction of the Y-axis is upward. code show as below:

GL.glScaled(1.0, 1.0, 1.0/100.0);

GL.glTranslatef(0.0f, -200.0f, 0.0f);

GL.glRotated(90.0, 1.0, 0.0, 0.0);

The main steps of constructing the three-dimensional ocean water body surface according to the polygonal contour line of the arbitrary sea area constructed by the user, and "projecting" the parallel contour line to generate the cube model of the ocean water body: according to the polygonal contour line of the arbitrary sea area constructed by the user, use GIS method to cut, The area outside the sea surface contour is masked to construct a three-dimensional ocean water body surface, and the main body of the ocean water cube model is generated by "projecting" parallel contour lines. Move the contour line down to the maximum depth of the digital elevation model of the seabed terrain along the Z axis, and use OpenGL to construct a rectangular surface at the inflection point between the two parallel contour lines and the upper and lower contour lines, and display it transparently. The size of the X-axis and Y-axis planes of the ocean water column depends on the size of the closed polygon drawn by the user in the two-dimensional electronic map. The depth of the ocean water in the Z-axis direction is the maximum depth of the digital elevation model of the seabed terrain.

The sea surface is mapped with the sea surface wave texture, the seabed terrain is converted into the OpenGL primitive through the digital elevation model, and the modeling steps are set with single color rendering and multi-light source parameter setting: use OpenGL to map the ocean wave texture on the top surface, map The position information of the sea surface comes from the two-dimensional contour line. Since the sea surface is an arbitrary polygon, the surround mode "mirror" is used to repeat and crop to "complement" the sea surface polygon mapping or crop texture, and the seabed terrain digital elevation model is first converted into a text file. format, and then describe it with OpenGL primitives, so as to convert it into a graphics function recognizable by OpenGL. The seabed terrain is rendered in a single color, and the elevation change is reflected by the position of the lighting viewpoint, the direction of the line of sight, and the setting of lighting parameters.

Obtain the cross-section of the physical quantity of the raster data set by the "projection" of the parallel contour lines and the stretching of the terrain simulation, and transparently display the surface of the ocean water body to obtain visualization effects from various angles. Steps: the side of the ocean water column is used to express the inversion of the ocean environment The change of data with depth, the sea surface contour line is mapped to the layered information of the marine environment inversion data through the "projection" method of parallel contour lines, and the transverse contour within the range of the two-dimensional contour line of the marine environment inversion data is obtained. section. The pixel of the preprocessed marine environment raster dataset is (x, y, value), which contains coordinates and physical quantities. The marine environment raster dataset is converted to OpenGL primitives through text files, and then stretched by terrain simulation, that is, the physical value value is used as the coordinate of the elevation direction Z, and stretched in the form of a digital elevation model to obtain significant and intuitive layered information. The surface of the ocean water body is displayed transparently so that the inversion data of each layered ocean environment can be viewed from any angle.

Compared with the prior art, the present invention has beneficial effects:

1) Real-time three-dimensional ocean water body modeling, effective use of marine environmental satellite remote sensing data, proposed a solution from satellite data to OpenGL modeling, greatly shortening the data processing cycle, compared with traditional ship survey data, the timeliness has been greatly improved;

2) The converted data is stored based on time visualization, which supports quick query of the spatio-temporal characteristics of massive remote sensing raster datasets;

3) The ocean water cube in any observation area can be constructed by the contour line construction method of the sea surface test area. This real-time volume construction method can better adapt to the needs of users;

4) Virtual reality modeling of marine water bodies is a new means of marine environment monitoring. After the modeling is completed, it can clearly reflect the changes in the physical quantities of the ocean environment retrieval data such as ocean temperature, salinity, and transparency, and can monitor the ocean environment well and predict the occurrence of marine natural disasters, such as red tides, etc.;

5) The present invention is based on RS and GIS environment, utilizes OpenGL as the modeling tool to realize the new means of three-dimensional marine water body modeling. Effective use of marine environment satellite remote sensing data, real-time three-dimensional ocean water body modeling is realized by delineating any observation area within the China Sea, and the visualization results are clear and intuitive. The invention has very wide application prospect in the field of marine environment monitoring.

Description of drawings

Fig. 1 is a schematic diagram of the RS marine environment inversion data source file format in the present invention;

Fig. 2 is the schematic diagram of the present invention's GIS-based marine environment inversion data processing method;

Fig. 3 is a schematic diagram of the time-based visual storage method of the present invention;

Fig. 4 is the coordinate system conversion schematic diagram before modeling of the present invention;

Fig. 5 is a schematic diagram of constructing a sea surface from the contour line of the sea surface test area of the present invention;

Fig. 6 is a schematic diagram of repetition and cropping of the surround mode "mirroring" in the present invention;

FIG. 7 is a schematic diagram of data preparation steps for scene generation in the present invention;

Fig. 8 is a schematic diagram of an ocean water scene generated by the present invention.

Detailed ways

The modeling method of ocean water body virtual reality is as follows:

1) Through the data conversion service, the text format of the original marine remote sensing environment inversion data is automatically converted into a raster dataset;

2) The converted data is stored based on time visualization, which supports quick query of the spatio-temporal characteristics of massive remote sensing raster datasets;

3) The spatial coordinate system setting of the OpenGL 3D ocean water scene, after Z-axis scaling, coordinate system translation to the screen along the vertical screen direction, coordinate system rotation, and X, Y-axis coordinate units unified to latitude and longitude coordinates, the scene coordinate system setting is completed;

4) Construct the surface of the three-dimensional ocean water body according to the polygonal contour line of any sea area constructed by the user, and generate the main body of the cube model of the ocean water body by "projecting" parallel contour lines;

5) Use the wave texture of the sea surface to map the sea surface, convert the seabed terrain into OpenGL primitives through the digital elevation model, and use single color rendering and multi-light source parameter settings to model;

6) Obtain the cross-section of the physical quantity of the raster data set by the "projection" of the parallel contour line and the stretching of the terrain simulation, and transparently display the surface of the ocean water body to obtain visualization effects from various angles.

The steps of automatically converting the text format of the original marine remote sensing environment inversion data into a raster dataset by means of data conversion services: the original ocean environment inversion data is in a hexadecimal text file format, as shown in Figure 1 , the specific format is shown in the following table:

name type Bytes the meaning read method Product char 20 Remote sensing product name ReadChars(20) unit char 16 The unit of physical quantity of remote sensing products ReadChars(16) cycle short 2 Product cycle (5 days, 10 days, 30 days) ReadInt16() Number short 2 The number of merged files ReadInt16() year short 2 start year ReadInt16()

Sunday short 2 Start Julian day ReadInt16() Eyear short 2 Termination year ReadInt16() Eday short 2 Terminate Julian Day ReadInt16() Lat_max float 4 The northernmost latitude ReadSingle() Lat_min float 4 Southernmost latitude ReadSingle() Lon_max float 4 Easternmost longitude ReadSingle() Lon_min float 4 most west longitude ReadSingle() Project char 20 Projection method ReadChars(20) R_lat float 4 Longitude resolution (degrees) ReadSingle() R_lon float 4 Latitude resolution (degrees) ReadSingle() Row short 2 The total number of grid data rows ReadInt16() Col short 2 The total number of grid data columns ReadInt16() Slope float 4 The slope of the conversion from grid data to physical quantities ReadSingle() Offset float 4 Intercept for conversion from grid data to physical quantities ReadSingle() Spare char 920 spare field ReadChars(920) value short Total number of rows × total number of columns physical value ReadInt16()

Read the Head file header and data body of the original marine environment inversion data into the memory in the form of a file stream, and use the method of looping rows and columns to read the physical quantities in the data block. Then write it into the raster dataset according to the data organization method of the raster dataset, that is, set the width, height, pixel size, spatial reference, and number of bands of the raster dataset according to the information in the header file. Data is written to the pixels in the pixel block. Figure 2 is a schematic diagram of the GIS-based marine environment inversion data processing method.

Use the Internet information server to detect the data files in the target folder, and delete the source files after conversion and storage.

System.Timers.Timer setTimer = new System.Timers.Timer(2000);

setTimer.Elapsed+=new ElapsedEventHandler(setTimer_Elapsed);

setTimer.Enabled = true;

setTimer.AutoReset = true;

setTimer. Start();

The converted data is stored based on time visualization, which supports quick query of the spatio-temporal characteristics of massive remote sensing raster datasets: the storage based on time visualization is the head file of the original marine environment inversion data The periodic value of the periodic product in the header is stored in the product metadata table, and the non-periodic product is stored as 0; the periodic time metadata table stores the start date (SDate) and end date (EDate) fields to store the start of the product respectively YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY thus the fields store the start time and end time minutes and seconds of the product. The instantaneous time metadata table stores the date (Date) and time (Time) of the instantaneous time point. Product time is stored using a collection of the above fields. The above time storage objects are consistent with the time types in the SQL standard, so the data sets in the time collection can be quickly queried by using the standard SQL language. The specific table storage method is shown in Figure 3.

The spatial coordinate system setting of the OpenGL three-dimensional ocean water scene, after Z-axis scaling, XY-axis coordinate plane translation to the screen along the vertical screen direction, coordinate system rotation and X, Y-axis coordinate units unified to longitude and latitude coordinates to complete the scene coordinates System setting steps: OpenGL default world coordinate system X-axis, Y-axis and Z-axis coordinate unit length is uniform, but considering the characteristics of ocean water body data, that is, the horizontal direction (X, Y) coordinate range is (180 degrees east longitude to 180 degrees west longitude, 90 degrees north latitude to 90 degrees south latitude), and the depth of the global ocean ranges from 0 meters to more than -10,000 meters. It will cause the Z-axis direction to be too steep, and the modeling effect is not good. Therefore, the unit length of the Z-axis coordinate is reduced to 1/100 of the original length, that is, the unit length of the X-axis and Y-axis is 100 on the Z-axis. The world coordinate system of the OpenGL scene and the XY axis plane of the eye coordinate system coincide with the screen plane, so the coordinate system needs to be translated in the screen along the vertical screen direction. The world coordinate system is a right-handed Cartesian coordinate system. The XY axis plane is parallel to the screen. The sea level of the generated scene is parallel to the screen. This is contrary to the common sense that the sea level is perpendicular to the direction of the human eye line of sight. The coordinate system should be rotated to the Z axis , the positive direction of the X-axis is horizontal to the right, and the positive direction of the Y-axis is upward. The renderings before and after the coordinate system conversion are shown in Figure 4. code show as below:

GL.glScaled(1.0, 1.0, 1.0/100.0);

GL.glTranslatef(0.0f, -200.0f, 0.0f);

GL.glRotated(90.0, 1.0, 0.0, 0.0);

The main steps of constructing the three-dimensional ocean water body surface according to the polygonal contour line of the arbitrary sea area constructed by the user, and "projecting" the parallel contour line to generate the cube model of the ocean water body: according to the polygonal contour line of the arbitrary sea area constructed by the user, use GIS method to cut, The area outside the sea surface contour is masked to construct a three-dimensional ocean water body surface, and the main body of the ocean water cube model is generated by "projecting" parallel contour lines. Move the contour line down to the maximum depth of the digital elevation model of the seabed terrain along the Z axis, and use OpenGL to construct a rectangular surface at the inflection point between the two parallel contour lines and the upper and lower contour lines, and display it transparently. The size of the X-axis and Y-axis planes of the ocean water column depends on the size of the closed polygon drawn by the user in the two-dimensional electronic map. The depth of the ocean water in the Z-axis direction is the maximum depth of the digital elevation model of the seabed terrain.

The main steps of constructing the three-dimensional ocean water body surface according to the arbitrary sea area polygon contour line constructed by the user, and generating the cube model of the ocean water body with parallel contour lines "projection" are as follows: after setting the three-dimensional space coordinate system of OpenGL, set its X axis, Y axis Consistent with the longitude and latitude spatial coordinates of the spatial data, use the GIS method to cut and mask the area outside the sea surface contour line according to the polygonal contour line of any sea area constructed by the user, and construct the three-dimensional ocean water body surface, as shown in Figure 5. The main body of the ocean water body cube model is generated by "projecting" parallel contour lines. The dimensions of the ocean water column in the X-axis and Y-axis planes depend on the size of any polygon drawn by the user in the two-dimensional electronic map, and the depth of the ocean water body in the Z-axis direction is the maximum depth of the seabed terrain digital elevation model.

The sea surface is mapped with the sea surface wave texture, the seabed terrain is converted into the OpenGL primitive through the digital elevation model, and the modeling steps are set with single color rendering and multi-light source parameter setting: use OpenGL to map the ocean wave texture on the top surface, map The position information of the sea surface comes from the two-dimensional contour line. Since the sea surface is an arbitrary polygon, the surround mode "mirror" is used to repeat and crop to "complement" the sea surface polygon mapping or crop texture, and the seabed terrain digital elevation model is first converted into a text file. format, and then describe it with OpenGL primitives, so as to convert it into a graphics function recognizable by OpenGL. The seabed terrain is rendered in a single color, and the elevation change is reflected by the position of the lighting viewpoint, the direction of the line of sight, and the setting of lighting parameters. The light source and line of sight settings are as follows:

//Define a moving light source that moves with the camera

static float[] ambient = {0.5f, 0.5f, 0.5f, 1.0f};

static float[] diffuseLight = {1.0f, 1.0f, 1.0f, 1.0f};

static float[] specularLight = {1.0f, 1.0f, 1.0f, 1.0f};

static float[] lightPosition = {0.0f, 400.0f, 200.0f, 1.0f};

//Initialize the light source

GL.glEnable(GL.GL_LIGHTING);

//Set the light source

GL.glLightfv(GL.GL_LIGHT0, GL.GL_AMBIENT, ambient);

GL.glLightfv(GL.GL_LIGHT0, GL.GL_DIFFUSE, diffuseLight);

GL.glLightfv(GL.GL_LIGHT0, GL.GL_SPECULAR, specularLight);

GL.glLightfv(GL.GL_LIGHT0, GL.GL_POSITION, lightPosition);

GL.glEnable(GL.GL_LIGHT0);

// Dynamically set the light source function

public static void SetLight()

{

Vector3vec = MyView.MyCamera.getPosition();

lightPosition=new float[]{vec.x+0.0000000100f,

vec.y - 0.000000003f, vec.z - 0.180f, 1.0f};

}

//View initialization vector value

Vector3zero = new Vector3(0.0f, 0.0f, 0.0f);

Vector3view = new Vector3(0.0f, 1.0f, 0.5f);

Vector3up = new Vector3(0.0f, 0.0f, 1.0f);

//Vector3 is a custom data type, which is a three-dimensional vector data

Position=zero;

View = view;

UpVector = up;

//Set the viewpoint position

public void setLook()

{

GL.gluLookAt(Position.x, Position.y, Position.z, View.x,

View.y, View.z, UpVector.x, UpVector.y, UpVector.z);

}

The above steps of obtaining the physical quantity cross-section of the marine environment inversion data by parallel contour line "projection" and terrain simulation stretching, and transparently displaying the surface of the ocean water body to obtain visualization effects from various angles: the side surface of the ocean water column is used to express the ocean environment reflection The data changes with the depth, through the "projection" method of parallel contour lines, that is, using the GIS method to cut and mask the area outside the sea surface contour line to map the sea surface contour line to each layer of the marine environment inversion data In terms of information, the cross-section within the scope of the two-dimensional contour line of the inversion data of the marine environment is obtained. The pixel of the preprocessed marine environment raster dataset is (x, y, value), including coordinates and physical quantities. The marine environment raster dataset is converted to OpenGL primitives through text files, and then stretched by terrain simulation, that is, the physical value value is used as the coordinate of the elevation direction Z, and stretched in the form of a digital elevation model to obtain significant and intuitive layered information. The surface of the ocean water body is displayed transparently so that the inversion data of each layered ocean environment can be viewed from any angle.

Example

Taking the ocean remote sensing temperature retrieval data in March 2006 as an example, first read the information in the header file in the form of file stream as follows:

name value name value name value Product SST Eyear 2006 Project Equal Lat/Lon unit Spend Eday 90 R_lat 28

Cycle 31 Lat_max 42.0000000000 R_lon 117.5 Number 31 Lat_min 14.0000000000 Row 1681 year 2006 Lon_max 130 Col 1501 Sunday 60 Lon_min 105 Slope 0 Offset -2

Second, store the information in the header file into the metadata table. Among them, the periodic value of the periodic product is stored in the metadata table, and the non-periodic product is stored as 0. Taking this data as an example, the periodic value is 31; the Julian day is converted into month and day, here the periodic product time The record table stores the start date (2006-03-01) and the end date (2006-03-31); the above time storage objects are consistent with the time types in the SQL standard, so the time can be quickly queried by using the standard SQL language Datasets within a collection.

Third, Z-axis scaling, XY-axis coordinate plane translation along the vertical screen direction to the screen, coordinate system rotation, and X, Y-axis coordinate units are unified to latitude and longitude coordinates to complete the setting of the scene coordinate system.

Fourth, the user defines any closed multi-deformation on the sea surface, raster data masks the pixels outside the contour line, and vector data clips the line segments outside the contour line. Ocean water bodies use the method of "projection" of parallel contour lines. Project the contour line to the seabed topographic surface, take the maximum valley point of the water depth DEM within the projection range, and use this point to construct a plane parallel to the sea surface. In this way, two adjacent parallel surfaces are formed. Then, connect the points on the upper and lower contour lines in turn to form a rectangular surface.

Fifth, the texture object adopts a two-dimensional sea surface ripple image in BMP format. When doing sea surface texture mapping, make sure that texture coordinates are assigned to each vertex. The scope of the observation area defined by the user in the China Sea area is uncertain, but the width and height of the BMP texture are fixed, so when the left, right, upper, and lower edges of the BMP image of sea surface ripples are adjacent to each other, in order to achieve a better connection effect , using the surround mode "mirror" to repeat and crop, and the part of the edge of the sea surface that is less than the size of a texture is supplemented by cropping.

Sixth, the seabed terrain is rendered in a single color. Before using OpenGL to draw a 3D seabed terrain model, set parameters such as light source, viewpoint position, and line of sight direction.

Seventh, the cross-section of ocean temperature, salinity, and transparency physical quantities is also obtained by using the method of constructing the contour line of the test area, and the physical quantity value is used as the elevation value, and is expressed in a single color and by setting light source parameters in the same way as terrain modeling changes in physical quantities. Since the physical quantity is a section located in the body, the transparency of the body surface needs to be set, and the transparency is in the interval (0, 1), which can be selected according to the needs.

Figure 7 is a three-dimensional model of the inversion data of marine water bodies and marine environment in the South China Sea in March 2006 created by the above method. The marine environment data here includes temperature and transparency, and adopts the method of layering coloring and stretching according to physical quantities, and uses the terrain simulation method of high and low fluctuations to reproduce the trend of physical quantity changes.

Claims (7)

1. the modeling method of an ocean water body virtual reality is characterized in that comprising the steps:

1) by the data-switching service manner, proto-ocean remote sensing environment inverting data text form is automatically converted to the raster data collection;

2) data after the conversion have been carried out storage based on the time visual means, supported the space-time characterisation of magnanimity remote sensing raster data collection is carried out fast query;

3) spatial coordinate system of the three-dimensional ocean water body scene of OpenGL is set, and finishes the setting of scene coordinate system through Z axle convergent-divergent, coordinate system along the translation in screen of vertical screen direction, coordinate system rotation and X, Y-axis coordinate unit unification to latitude and longitude coordinates;

4) any marine site polygonal wheel profile according to user's structure makes up three-dimensional ocean water body surface, generates the main body of ocean water body cube model with parallel contour line " projection ";

5) with the wave of the sea texture sea table is carried out pinup picture, submarine topography is converted to OpenGL primitive via digital elevation model, plays up with the multiple light courcess parameter with solid color modeling is set;

6) obtain raster data collection physical quantity xsect by parallel contour line " projection " and terrain simulation stretching, transparent demonstration ocean water body surface obtains the effect of visualization of all angles.

2. according to the modeling method of the described a kind of ocean water body virtual reality of claim, it is characterized in that described by the data-switching service manner, proto-ocean remote sensing environment inverting data text form is automatically converted to raster data collection step: be that Head file header and data volume with proto-ocean environment inverting data reads in internal memory with the form of document flow, again its data organization mode according to the raster data collection is write the raster data collection, utilize the data file under the Internet information server detection destination folder, conversion warehouse-in back deletion source file.

3. according to the modeling method of the described a kind of ocean water body virtual reality of claim, it is characterized in that described data after the conversion having been carried out storage based on the time visual means, support is carried out the fast query step to the space-time characterisation of magnanimity remote sensing raster data collection: the storage based on the time visual means is with the production life cycle in the Head file header of proto-ocean environment inverting data, product rise time section, product rise time point is kept at the product metadata table respectively, periodically in tempon tables of data and the instantaneity tempon tables of data, with standard SQL time query statement, can inquire the data set in the time set fast.

4. according to the modeling method of the described a kind of ocean water body virtual reality of claim, the spatial coordinate system that it is characterized in that the three-dimensional ocean water body scene of described OpenGL is set, through Z axle convergent-divergent, coordinate system is along the translation in screen of vertical screen direction, coordinate system rotation and X, Y-axis coordinate unit unification to latitude and longitude coordinates is finished the scene coordinate system step is set: the X-axis of the world coordinate system of OpenGL acquiescence, Y-axis and Z axial coordinate unit length are unified, but consider the feature of ocean water body data, be that horizontal direction X coordinate range is that east longitude 180 is spent to west longitude 180 degree, the Y coordinate range is that north latitude 90 is spent to south latitude 90 degree, and the global ocean degree of depth does not wait by 0 meter to more than-10000 meter, X-axis, the coordinate unit length of Y direction and Z-direction differs more than the 2 multiple magnitudes, then can cause Z-direction too precipitous, the modeling poor effect, so, the unit length of Z axial coordinate is reduced into 1/100 of original length, it is X-axis, 1 unit length of Y-axis, on the Z axle 100, the XY axial plane of the world coordinate system of OpenGL scene and eye coordinates system coincides with screen plane, so need be with coordinate system along the translation in screen of vertical screen direction, world coordinate system is the right-handed Cartesian coordinate system system, the XY axial plane is parallel with screen, the sea level that generates scene parallels with screen, the general knowledge that this and sea level should be in horizontal direction is not inconsistent, therefore, will with coordinate system rotation to Z axially on, the X-axis level is to the right a positive dirction, Y-axis upwards is positive dirction.

5. according to the modeling method of the described a kind of ocean water body virtual reality of claim, it is characterized in that described any marine site polygonal wheel profile according to user's structure makes up three-dimensional ocean water body surface, generate the main body step of ocean water body cube model with parallel contour line " projection ": according to any marine site polygonal wheel profile of user's structure, utilize the method cutting of GIS, the outer zone of table skeleton line, mask sea, make up three-dimensional ocean water body surface, generate the main body of ocean water body cube model with parallel contour line " projection ", outline line is axially moved to the depth capacity of submarine topography digital elevation model down along Z, flex point between two parallel contour lines on the above lower whorl profile links to each other and utilizes OpenGL structure rectangular surfaces, and transparent demonstration, ocean water body column X-axis, size in the Y-axis plane depends on the size of the closed polygon that the user draws in two-dimentional electronic chart, ocean water body degree of depth Z-direction is the depth capacity of submarine topography digital elevation model.

6. according to the modeling method of the described a kind of ocean water body virtual reality of claim, it is characterized in that describedly sea table being carried out pinup picture with the wave of the sea texture, submarine topography is converted to OpenGL primitive via digital elevation model, play up with the multiple light courcess parameter with solid color modeling procedure is set: utilize OpenGL to carry out the ocean wave texture at end face, the positional information of pinup picture derives from 2-d contour, Yin Haibiao is an arbitrary polygon, repeat to come table polygon mapping of " supplying " sea or cut texture so adopt with cutting around pattern " mirror image ", the submarine topography digital elevation model is converted to text file format earlier, describe out with OpenGL primitive again, thereby change into the discernible graph function of OpenGL, submarine topography adopts solid color to play up, and utilizes the illumination viewpoint position, direction of visual lines, illumination parameter is provided with the variation of reflection elevation.

7. according to the modeling method of the described a kind of ocean water body virtual reality of claim, it is characterized in that described the stretching by parallel contour line " projection " and terrain simulation obtains raster data collection physical quantity xsect, transparent demonstration ocean water body surface obtains the effect of visualization step of all angles: the side of ocean water body column is used for expressing the situation of marine environment inverting data with change in depth, mode by parallel contour line " projection " is mapped to extra large table skeleton line on each hierarchical information of marine environment inverting data, obtain the interior xsect of 2-d contour scope of marine environment inverting data, pixel through pretreated marine environment raster data collection is (x, y, value), wherein comprise coordinate and physical quantity, marine environment raster data collection is converted to OpenGL primitive via text, stretch by terrain simulation again, be about to the coordinate of magnitude of physical quantity value as elevation direction Z, stretching in the mode of digital elevation model obtains hierarchical information intuitively, and the ocean water body surface adopts transparent demonstration so that from each layering marine environment inverting data of arbitrarily angled perspective.

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