CN105631934A - Three-dimensional visualization information system under network environment - Google Patents

Abstract

Some progress has been made in the study of a three-dimensional terrain visualization information system under network environment, but a mature, simple and practicable method is still lacked in the aspects of mass data management and transmission, large-scale scene modeling, realistic display and the like, and based on the status quo at home and aboard, the principle of integrating an ellipsoid quad-tree spatial index technology for rapidly accessing multi-scale multi-level geographic data and a stream transmission and detail level rendering technology is discussed. A simplified algorithm for a large-scale terrain scene using apparent correlation and topographic gradient as criteria and using multi-system wavelet and level triangulation network technology as a core is proposed. According to the theories and technologies, by means of a COM technology, a network-based three-dimensional visualization system is designed. Mass spatial data are published on PCs, thereby satisfying requirements for concurrent browse, query and analysis of multiple users. The system has good application prospects in the aspects of military simulation training, urban planning and the like.

Description

Three-dimensional visualization information system under a kind of network environment

Technical field

A kind of technical field in three-dimensional visible in computer realm.

Background technology

At present, along with " digital earth, " digital province and digital city ", the proposition of " digital cells " and construction, and the fast development of information and remotely-sensed data acquiring technology, networking is moved towards in the service largely promoting conventional two-dimensional GIS, the form of expression develops to 3 D stereo direction, the ability of software transmission and process mass data is just proposed challenge by this. arouses great concern with the digital virtual system that D terrain landscape model is main contents, and it is increasingly becoming three-dimension GIS, one of the main flow [1] of virtual reality development. although many researcheres have been developed for three-dimension GIS prototype system, make three-dimension GIS technology at mineral resource value, many fields such as digital city are applied, but really study the generalized information system of latticed form and the document of terrain visualization system and application system at present, little Network Three-dimensional visualization system it is critical to solve the quick real-time Transmission of Large Copacity spatial data, the management of Dynamic Announce and multi-source mass data and efficient index.

Summary of the invention

1997, Lindstrom et al. proposes Preliminary design model VGIS [3] of the three-dimensional earth, research for the virtual three-dimensional earth is made that good exploration. Keyhole company of the U.S. [4] is comparatively perfect up to now Network Three-dimensional geographic information systems at the EarthSystem that calendar year 2001 develops. but the configuration particularly video card of computer is required significantly high by it, generally operate in .Teler et al. in the client being furnished with NVIDIA video card to propose server end and only render the element of lowest level, and result is returned in the form of images client, and other LODs passes to client as threedimensional model, it is fewer than the time of directly transmission threedimensional model plus the image transmitting time that visual work carries out the LOD render time that advantage of this is that minimum a layer in client, but when a great number of elements and client computer are run simultaneously, even if the visualization process of lowest level data also can be extremely complex, the overload of server. provide a development environment based on client/server virtual scene [6] although .WorldToolKit can provide high-quality figure with the OpenGLVizserver of Scense8 and the SGI virtual environment software WorldToolKit developed, but all of render work and all complete on SGI server, three-dimensional scenic passes in client as picture, even if the allocation of computer of client is significantly high, it is also required to the server of costliness.

The present invention is the data publication of the three-dimension visible sysem GeoVirtual under Internet/Intranet environment and the method .GeoVirtual that realizes of three dimensional display provides a kind of new way browsing the earth, user uses mouse (or query manipulation) just the earth can be positioned roaming, its less demanding to client. owing to adopting a set of core technology of oneself, making between client objects and server object can direct dialogue, reasonable distribution system loading, thus Web server will not over-burden. The basic demand of Network Three-dimensional visualization system is that three-dimensional scenic can quickly be transferred to multiple client; reduce network congestion to greatest extent; the complexity of scene to adapt to the actual treatment ability of client computer. considers: (1) is if being placed on server end by the work that renders of scene; during multi-user access, even if the drafting of lowest level element all can exceed the service ability of server; (2) system rendered based on server, server hardware configuration requirement is significantly high, and the picture being transferred to client can only describe two-dimensional signal, lacks mutual and conversion function. The structure system of the network GIS GeoVirtual of our design. this structure has following features: (1) is owing to have employed efficient Spatial Data Index Technology, progressive transmission technology and Terrain Simplification algorithm; the display speed of client scene is unrelated with data volume size; meet the needs of Multi-Client Concurrency Access, and reduce network blockage and transmission time to greatest extent; (2) asynchronous multithreading is adopted, can at backstage Real time request and process terrain data while client computer Visual Scene.

Web server mainly includes some data bases and an off-line number

Data preprocess module. the storage of its primary responsibility mass data, index, compression etc., and requested data are submitted to client .DEM data base, texture database and vector database: the DEM in the whole world, vector data and data texturing are according to resolution, locus is stored in data base by different level, and realizing Seamless integration-by internal correlation. index module carries out quick-searching according to the request of client in full storehouse, automatically the data of different levels are called. three-dimensional modeling data storehouse: have recorded the title of model in data base, coordinate, texture and the description information that some are important, simulation in order to city or community three-dimensional building. attribute database: have recorded the coordinate of landform, annotation, the attributes such as the information of characteristic point, in order to realize the inquiry of geomorphological features. client is the interface mutual with long-distance user and interface, communication is carried out by http agreement and server. it uses three-tier structure system to realize, i.e. VC++, the scene management thread of JavaScript and HTML. client application is responsible for asking specific region to Web server, the data of certain resolution and type. when data are positioned on a node of quaternary tree, client is data allocation space in shared high-level cache and sends request by shared drive Priority Queues to server, the rank of association requests is determined by scene rendering thread. the static state in current layer quaternary tree node, it being placed in one group of Hash table depending on related data. Hash table has just initialized when system start-up, which node outside at table known by manager, thus without the data to server request redundancy.

The present invention utilizes the stream capacity expansion of multi-level transmission method based on the out-of-core algorithm of level of detail, combine and render depending on relevant geometry flow, prefetch, inside and outside buffer memory scheduling theory technology, apply it to large scale, during high-resolution terrain data transmits and renders. in order to reduce the consumption of internal memory, the node building three-dimensional scenic adopts arithmetic coding compression, first transmit model thicker in visible child node, and it is retained in client internal memory, the scene that progressive visualization is higher level. if traversal would stop, just by thicker level of detail model rendering. search in the process of current node to be rendered in traversal quad-tree structure, stream and prefetching process are divided into two asynchronous threads carry out. data required in mutual process are put in the buffer, each level of detail retains the buffer memory of data block, if block uses immediately, it is stored in memory cache, otherwise, it being placed in disk buffering. the application program of client is according to the machine hardware configuration, data yardstick and based on looking relevant principle, determine suitable m-band wavelets, static error and dynamic error, the triangulation network is utilized to build Three-dimensional Multi-resolution scene. the urban area of several meters is only had from the large scene that resolution is several kilometers to resolution, if scene changes is too fast, landform manager is crossed over quaternary tree and is navigated to the speed of correct position and can lag behind user and convert the speed of scene, this administrative mechanism allows quaternary tree can quickly navigate to suitable locus to obtain important attribute information and geographical space Bounding Box, thus determining which data and models show are in current what comes into a driver's body.

Accelerating display speed while keeping three-dimensional scenic rendering quality is visualization field key problems-solving. a lot of lists of references propose and simplify terrain scene [12 with binary tree or quaternary tree, 13], if the resolution of data is significantly high, only lean on the amount of calculation that binary tree (or quaternary tree) simplifies very big, consumption internal memory is many, it is difficult to the real-time visual of extensive DEM. in order to rapidly data model is simplified within given range of error, set forth herein and simplify DEM and texture in real time by multi-scales Wavelet Transform and level triangle technology.

Small echo has the good ken and frequency domain characteristic, and the topographic details being omitted can reconstruct out by suitable wavelet basis, utilizes small echo

Basic sequence, have only to little point and just can approach initial data. m-band wavelets theoretical [14 ~ 16] in symmetry, slickness etc. compared with binary wavelet, having the feature of its uniqueness, it can solve the indeterminable problem of binary wavelet. m-band wavelets former data are resolved into 1 low-frequency component (profile of landform) andM21 radio-frequency components (detail characteristic). low-frequency component can generate again new high and low frequency composition through wavelet transformation. the characteristic according to image and DEMs, provide the multi-scales Wavelet Transform formula the being suitable for simplifying relief modeljLayer low-frequency componentaj,k,l}��

In m-band wavelets catabolic process, thej+ 1 layeraj+1,k,lLow-frequency component can be good at reservationjLayeraj,k,lEssential information. the application program of client can adopt suitable m-band wavelets to build landform according to the size of the hardware configuration of oneself and data yardstick, subsequently, to the filtering data after multi-scales Wavelet Transform, multiresolution triangle is adopted to build topographical surface model. author is correlated with topography and geomorphology fluctuating as criterion to look, it is proposed to set up with static error and the dynamic of dynamic error implementation model.

In order to compare the superiority of algorithm herein, VDPM method [13] that this paper algorithm and Hoppe are proposed by author, initial data do not simplify and directly display, frame rate and memory consumption have done contrast. can be seen that, along with DEM sampling number purpose increases, methods herein is better than VDPM method in frame rate and memory consumption, about can keep the speed of 25 frames/second. owing to the VDPM triangulation network models

Need to consume internal memory between triangle and keep topological relation, find suitable summit and need the regular hour. and methods herein first passes through multi-scales Wavelet Transform and rejects redundant points, retain crucial summit, then earth surface model is built with filtering data, substantially accelerate modeling speed, reduce the consumption of internal memory. under different static error �� and dynamic error ��, a few width multiresolution terrain models, simultaneous quantitative describes the number rendering triangle and corresponding frame rate.

Claims (5)

1. under a network environment, three-dimensional visualization information system is characterized in that the basic demand of Network Three-dimensional visualization system is that three-dimensional scenic can quickly be transferred to multiple client, reducing network congestion to greatest extent, the complexity of scene to adapt to the actual treatment ability of client computer.

2. according to claim 1, if it is characterized in that the work that renders of scene is placed on server end by 1.; During multi-user access, even if the drafting of lowest level element all can exceed the service ability of server; 2. the system rendered based on server; Server hardware configuration requirement is significantly high, and the picture being transferred to client can only describe two-dimensional signal, lacks mutual and conversion function.

3. according to its feature of claim 2 owing to have employed efficient Spatial Data Index Technology, progressive transmission technology and Terrain Simplification algorithm.

4. the display speed of client scene is unrelated with data volume size, meets the needs of Multi-Client Concurrency Access, and reduces network blockage and transmission time to greatest extent.

5. adopt asynchronous multithreading, can at backstage Real time request and process terrain data while client computer Visual Scene.