CN117911598A - Rendering method of native oblique photography OSGB data in illusion engine - Google Patents

Abstract

The invention provides a rendering method of native oblique photography OSGB data in a illusion engine, which comprises the following steps: providing a native oblique photography OSGB data file; loading a root LOD model, comprising: reading OSGB data files by using a C++ library provided by an OSG three-dimensional graphic engine, and analyzing files associated with a root LOD model; using Unreal Engine to load OSGB data files and generating index files of all files at the same time, wherein multithreading is adopted to perform file reading operation when loading OSGB data files; generating cache data for the loaded model; and integrating the loaded data and rendering by using Unreal Engine, wherein the rendering method controls the use peak value of the whole memory and the video memory when the OSGB data file is loaded. The rendering method of the original oblique photography OSGB data in the illusion engine can avoid the flow of format conversion, reduce the time, hardware and storage cost in the implementation process, solve the problem of difficult data updating and improve the user experience.

Description

Rendering method of native oblique photography OSGB data in illusion engine

Technical Field

The invention relates to the technical field of image data processing, in particular to a rendering method of native oblique photography OSGB data in a illusion engine, and specifically relates to a high-speed rendering method of native oblique photography OSGB data in a digital city in the illusion engine.

Background

With the development of digital mapping technology, the three-dimensional real-scene model is widely applied to the construction of digital cities by three-dimensional visual characteristics, and the construction mode of the three-dimensional real-scene model mainly comprises three-dimensional laser scanning, oblique photography and other modes, wherein the oblique photography method has the measurement characteristics of large range, high precision, high definition and the like, can visually reflect the properties of the appearance, position, height and the like of ground features, effectively improves the measurement effect and mapping precision, and reduces the three-dimensional modeling cost of the cities.

The oblique photography technology acquires images from five different angles of one vertical and four inclinations to obtain rich high-resolution textures of the top surface and the side view of the building, can truly reflect the condition of the ground object, can acquire object texture information with high precision, and can generate a real three-dimensional city model through advanced positioning, fusion, modeling and other technologies. Information is acquired through multiple angles of the multi-lens camera, three-dimensional coordinate information is available for each point on the image in cooperation with control point or image POS information, meanwhile, measurement can be conducted on any point line and plane based on image data, centimeter-level measurement accuracy is obtained, and a three-dimensional geographic information model is generated.

The aerial image by using the oblique photography technology can be processed by modeling software to output oblique photography three-dimensional data, and OSGB data are the most in the oblique photography three-dimensional data. Currently, the three-dimensional model of oblique photography on the market, especially the three-dimensional model data of oblique photography processed by Smart3D, is generally organized in a Binary-stored OSGB format with embedded link texture data (. Jpg), and Open SCENE GRAGH Binary is a full name of OSGB. In the construction of digital cities, these OSGB data need to be imported into a phantom ENGINE (UE) tool such as "Unreal" to be rendered for display. At present, the conventional technical processes are mainly three, which are complicated, and all the three schemes need to be loaded/imported into a UE engine by various modes after format conversion, and include:

Scheme one, open source flow (free): (1) Using CesiumLab to convert OSGB file to the public format of.3 dtiles; (2) The loading was performed using Cesium for Unreal plug-in provided by Cesium authorities.

Scheme two, closed source flow (payment): (1) Converting OSGB files into a private format by using a hypergraph or a flying platform; (2) loading using a proprietary authorization plug-in.

Scheme three, non-professional flow (free): (1) Using various tools to convert OSGB files into conventional model formats such as FBX, OBJ and the like; (2) imported using UE native mode (static).

The three schemes described above have the following drawbacks in common:

(1) The time and hardware costs are too high: converting formats is very time consuming, takes a long time to convert, and is highly dependent on high performance devices, requiring high performance devices to at least reach: memory >64G, CPU core number >16, mass hard disk storage device, and video memory >8G.

(2) The storage cost is high: the converted format brings a new set of oblique photography data, meaning that the user needs to keep two parts of data (OSGB parts, one part of the converted format) of almost the same size if archiving is needed.

(3) Updating data is difficult: the conversion format means that once metadata changes, the metadata needs to be converted again, and if the data size of OSGB is 150G, partial data update needs to be performed, which means that the user has to perform format conversion again, and the cost of time is doubled, or the data needs to be sliced, and the conversion is performed in blocks.

(4) The user experience is poor: no matter what loading mode is adopted, no matter the loading mode is adopted, the loading mode is adopted by the own plug-in or the original leading-in mode of the UE, various optimization problems such as jamming, overlarge memory/video memory and the like can occur, because oblique photography is used to the professional GIS (geographic information system ) industry after all, and game engine users are used to high frame rate, so that the current scheme is only 'enough' in the eyes of professionals, but in smart cities, the professional proportion of GIS is less than half, most smart city platforms are smoothly operated, and once the GIS modules are entered, the whole platform is jammed, and the experience is extremely poor.

Disclosure of Invention

The present invention aims to at least partially overcome the drawbacks of the prior art and provide a method for rendering native oblique photography OSGB data in a illusive engine.

The invention also aims to provide a rendering method of the native oblique photography OSGB data in the illusion engine, which can avoid the flow of format conversion.

The invention also aims to provide a rendering method of the native oblique photography OSGB data in the illusion engine, which reduces the time, hardware and storage cost in the implementation process.

The invention also aims to provide a rendering method of the native oblique photography OSGB data in the illusion engine, which solves the problem of difficult data updating.

In order to achieve one of the above objects or purposes, the technical solution of the present invention is as follows:

a method of rendering native oblique photography OSGB data in a illusion engine, the rendering method comprising:

step 100: providing a native oblique photography OSGB data file;

Step 200: loading a root LOD model, comprising: reading OSGB data files by using a C++ library provided by an OSG three-dimensional graphic engine, and analyzing files associated with a root LOD model;

Step 300: using Unreal Engine to load OSGB data files and generating index files of all files at the same time, wherein multithreading is adopted to perform file reading operation when loading OSGB data files;

Step 400: generating cache data for the loaded model; and

Step 500: integrating the loaded data, rendering with Unreal Engine,

The rendering method controls the use peak value of the whole memory and the video memory when loading OSGB data files.

In accordance with a preferred embodiment of the present invention, in step 200, the total number of root LOD models is calculated, and if the total number of root LOD models is greater than 100, model merging and face reduction processes are performed to reduce the total number of root LOD models.

In accordance with a preferred embodiment of the present invention, in step 300, the index file is stored while the OSGB data files are being loaded, storing the parent-child file relationships for all files.

According to a preferred embodiment of the present invention, the rendering method further comprises: the index file is read when the OSGB data file is again loaded using Unreal Engine.

In accordance with a preferred embodiment of the present invention, in step 400, the data within OSGB data files is stored as data suitable for Unreal Engine reading.

According to a preferred embodiment of the present invention, the data suitable for Unreal Engine reads includes vertices, order of lines, texture map coordinates, maps, and mesh levels.

According to a preferred embodiment of the present invention, the rendering method further comprises: limit verification is performed during loading OSGB of the data file, so that the condition that a collision peak crashes in the continuous loading and unloading process can be avoided.

According to a preferred embodiment of the invention, in the rendering method, the OSGB data files are directly loaded OSGB data files using Unreal Engine without format conversion.

The invention has the beneficial effects that: the rendering method of the original oblique photography OSGB data in the illusion engine avoids the flow of format conversion, so that the conversion time and high-performance hardware required by conversion do not exist, and the problems of overhigh time and hardware cost existing in the existing similar method are solved; the native oblique photography OSGB data rendering method in the illusion engine of the present invention does not require additional storage costs, as it does not require storing the format-converted file; the rendering method of the original oblique photography OSGB data in the illusion engine uses OSGB source file to load directly, when the file is updated, the latest version can be loaded and checked at any time, and the original oblique photography OSGB data is dynamically loaded without closing the engine, so that the problem of difficult updating of the data in the existing method is solved; in addition, as a plurality of optimization operations are performed during loading, and the performance of the UE engine is optimized in a matching way, the basic fps is greater than or equal to 30fps no matter in the loading process or after loading is finished, and the display end can obtain smooth operation experience.

Drawings

FIG. 1 is a flow chart of a method of rendering native oblique photography OSGB data in a illusion engine according to the present invention;

Fig. 2 is a schematic diagram of a method for rendering native oblique photography OSGB data in a illusion engine, according to one embodiment of the invention.

Detailed Description

Exemplary embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein the same or similar reference numerals denote the same or similar elements. Furthermore, in the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in the drawings in order to simplify the drawings.

In the description of the present disclosure, reference is made to a number of commonly used technical terms, which for the sake of clarity will first be described:

UE and Unreal: UE and Unreal are shorthand for UNREAL ENGINE (illusive engine), developed by Epic, are one of the most well-known game engines in the world.

LOD: LOD technology, i.e., level of Detail, is abbreviated to multi-level of Detail. The LOD technology is to determine the resource allocation of object rendering according to the position and importance of the nodes of the object model in the display environment, and reduce the number of planes and the detail of non-important objects, so as to obtain high-efficiency rendering operation.

OSGB: the usual oblique photography standard format, oblique three-dimensional model data processed by Smart3D, is the OSGB format stored in binary with embedded linked texture data (.jpg). OSGB-format oblique photography model, LOD data with multi-level resolution are built in the production process of the model, the LOD is a triangular net model built according to the dense point cloud after being thinned, and in the browsing process of a three-dimensional scene, transition among different levels is smooth and no kick feel exists.

OSG (Open SCENE GRAPH): OSG is a high-performance open source three-dimensional graphics engine, which is an open source code, and cross-platform graphics development kit.

Smart3D: smart3D software is a kind of realistic modeling software, and it carries out full-automatic three-dimensional modeling according to images acquired by various sensors for static objects.

GIS: the geographic information system (Geographic Information System or geo-Information system), sometimes referred to as "geoscience information system" or "resource and environment information system", is a specific and very important spatial information system, which is a technical system for collecting, storing, managing, computing, analyzing, displaying and describing related geographic distribution data under the support of computer hardware and software systems. The geographic information system processes and manages various geographic space entity data and relationships thereof, including space positioning data, graphic data, remote sensing image data, attribute data and the like, and is used for analyzing and processing various phenomena and processes distributed in a certain geographic area, so as to solve the problems of complex planning, decision making and management.

UV: UV is a short term for UVW, and omitted because the W coordinate is not commonly used, it means that the texture map coordinate is interrelated with the XYZ coordinate of the model, and UV defines the position information of each point on the picture. The process of reasonably tiling a three-dimensional surface on a two-dimensional canvas using software is known as UV spreading, also known as UV dismantling. Each three-dimensional model consists of a plurality of surfaces, and the working principle of UV disassembly is to disassemble the three-dimensional shapes into a plurality of two-dimensional surfaces, so that mapping work can be more conveniently carried out.

According to the present general inventive concept, there is provided a rendering method of native oblique photography OSGB data in a illusion engine, as shown in fig. 1, the rendering method including:

step 100: providing a native oblique photography OSGB data file;

Step 200: loading a root LOD model, comprising: reading OSGB data files by using a C++ library provided by an OSG three-dimensional graphic engine, and analyzing files associated with a root LOD model;

Step 300: using Unreal Engine to load OSGB data files and generating index files of all files at the same time, wherein multithreading is adopted to perform file reading operation when loading OSGB data files;

Step 400: generating cache data for the loaded model; and

Step 500: integrating the loaded data, rendering with Unreal Engine,

The rendering method controls the use peak value of the whole memory and the video memory when loading OSGB data files.

In accordance with a preferred embodiment of the present invention, in step 200, the total number of root LOD models is calculated, and if the total number of root LOD models is greater than 100, model merging and face reduction processes are performed to reduce the total number of root LOD models.

In accordance with a preferred embodiment of the present invention, in step 300, the index file is stored while the OSGB data files are being loaded, storing the parent-child file relationships for all files.

According to a preferred embodiment of the present invention, the rendering method further comprises: the index file is read when the OSGB data file is again loaded using Unreal Engine.

In accordance with a preferred embodiment of the present invention, in step 400, the data within OSGB data files is stored as data suitable for Unreal Engine reading.

According to a preferred embodiment of the present invention, the data suitable for Unreal Engine reads includes vertices, order of lines, texture map coordinates, maps, and mesh levels.

According to a preferred embodiment of the present invention, the rendering method further comprises: limit verification is performed during loading OSGB of the data file, so that the condition that a collision peak crashes in the continuous loading and unloading process can be avoided.

According to a preferred embodiment of the invention, in the rendering method, the OSGB data files are directly loaded OSGB data files using Unreal Engine without format conversion.

The invention has the beneficial effects that: the rendering method of the original oblique photography OSGB data in the illusion engine avoids the flow of format conversion, so that the conversion time and high-performance hardware required by conversion do not exist, and the problems of overhigh time and hardware cost existing in the existing similar method are solved; the native oblique photography OSGB data rendering method in the illusion engine of the present invention does not require additional storage costs, as it does not require storing the format-converted file; the rendering method of the original oblique photography OSGB data in the illusion engine uses OSGB source file to load directly, when the file is updated, the latest version can be loaded and checked at any time, and the original oblique photography OSGB data is dynamically loaded without closing the engine, so that the problem of difficult updating of the data in the existing method is solved; in addition, as a plurality of optimization operations are performed during loading, and the performance of the UE engine is optimized in a matching way, the basic fps is greater than or equal to 30fps no matter in the loading process or after loading is finished, and the display end can obtain smooth operation experience.

The invention is described in detail below in connection with a specific embodiment for native oblique photography OSGB data in a digital city, loaded into a virtual engine such as UNREAL ENGINE for rendering for display, comprising the steps of:

Step 100: a native tilt camera OSGB data file is provided, the OSGB data file may be a Smart3D production tilt model, and the derived OSGB data file, the OSGB data file may also be from other data format file converted OSGB data files.

Step 200: loading root LOD model

Reading OSGB data files by using a C++ library provided by an OSG (three-dimensional graphic engine) official, analyzing files associated with root LOD models, once the total number of the root LOD models is found to be more than 100, performing model combination and face reduction to reduce the total number of the root LOD models, so that most root LODs can be loaded instantaneously when data is input, the whole loading process becomes more natural, and the models can be seen only after waiting for a long time when the data is input.

OSGB the tilt model is of inverted pyramid structure, the root LOD is the least and the most ambiguous, the layer LOD mainly bears the original model display, the precision requirement is low, but the layer is the most hardware performance consuming in the conventional software processing, because after all, the combination and face reduction are needed, so that in most tilt model suppliers, the problem that the total quantity of the root LOD model is large due to insufficient machine memory can occur, for example: the OSGB tilt model covers a region of one thousand square meters and is processed into a root LOD model of one hundred and ten square meters, and the model can be normally used at present, but if the total size is ten thousand square meters, the computer can only process the root LOD model of one thousand and ten square meters, so that the loading is too slow-!

Here, the LOD model is also called a level of Detail (LOD) model, which is a real-time three-dimensional computer graphics technology, and its working principle is: when the viewpoint is close to the object, the detail of the model which can be observed is rich; the observed details are progressively blurred as the viewpoint moves away from the model. The system selects corresponding details for display according to certain judging conditions, so that time waste caused by drawing details with relatively little meaning is avoided, and meanwhile, the relation between the picture continuity and the model resolution is effectively coordinated.

Before loading starts, the invention can judge whether the OSGB needs to optimize the root LOD, so as to avoid the situation that the original data is poor and the data cannot be used better.

Step 300: the OSGB data file is loaded using Unreal Engine while the index file for all files is generated, wherein the file read operation is performed using multithreading while the OSGB data file is loaded. The OSGB data files adopt a tree structure data storage mode, the chain access of the Lod0 file linked Lod1 file can be necessarily generated during loading, in order to facilitate secondary loading and reloading, a special file index file is stored, parent-child file relations of all files are stored, and subsequent secondary loading can be directly read without confirming child-level positions next to file reading.

The OSGB inclined model is of an inverted pyramid structure, for example, the Lod-0 is linked with the Lod-1 and the Lod-2, so that quick cross-file reading cannot be realized, each parent level needs to be read next to each other, the loading speed is slower (but the mode is correct when the ultra-large-volume model files are stored), the integral index file of the inclined model can be generated in the loading process, and the problem that the input/output (IO) time is overlong because each layer of LOD files are required to be read specially in the secondary loading process is avoided.

In addition, the native oblique photography OSGB data rendering method in the illusion engine of the present invention employs multithreading for file read operations when loading OSGB data files. Because the UE engine follows the logic of main thread rendering, file IO operation cannot be executed in the main thread, otherwise, the whole loading process picture is blocked and cannot be operated, OSGB data belongs to the logic of continuous loading and unloading, and repeated file IO cannot be avoided.

Because OSGB files are in an inverted pyramid structure and are mutually related to form a tree structure, when the files are read, a great number of related reading operations exist, so that normal file reading cannot reach the highest speed.

Step 400: generating cached data for loaded models

The OSGB document is a grid recording mode unique to OSG authorities, and in order to increase the loading speed, the present invention stores the data in OSGB as data (vertex, line sequence, texture map coordinates (UV), map, grid level, etc.) more suitable for UE to read. The generation of the cache data does not need special generation, and the loaded file is automatically generated only when the cache data is used, and the cache data is directly loaded after the cache data is generated, so that waste of redundant resources is avoided.

Because of the characteristics of each engine platform, the characteristic model formats of each engine are greatly different from each other, so that the oblique photography model format OSGB created by the OSG official is more suitable for the official engine display in order to conveniently adapt to various functions such as loading, unloading, rendering and calculating. The OSGB file is in a common GIS data format, and in order to realize the repeated and rapid loading of the OSGB file, the data cache file special for the UE engine can be stored while loading, so that the loading speed can be increased by tens of times when a user uses the file for the second time, and the slow loading is avoided.

Step 500: the loaded data is integrated and rendered using Unreal Engine.

When loading, controlling the whole memory and the video memory: most of oblique loading stays at the standard capable of loading rather than paying attention to the whole life cycle (in the current age, the memory is not mainly 4g, but 16g is taken as everybody, and the work stations 32g and 64g start), so that most of the current schemes do not pay attention to the limit, and the invention also performs limit verification during loading and ensures that the machine can not crash during the continuous loading and unloading process.

The peak control of memory and video memory is a precondition for complete functionality, but the need is not emphasized by current commercial solutions, and the present invention puts the functionality into the necessary flow.

The rendering method of the native oblique photography OSGB data in the illusion engine has the following advantages:

The advantages are as follows: the data is directly loaded by using the original file without format conversion, so that time waste caused by conversion is avoided, high-performance hardware support is not needed, and the data is used immediately;

The advantages are as follows: after the oblique data is manufactured, the data provider gives the data, only stores one copy of the data, and does not need to store other data in a secondary conversion format, so that the waste of storage space is avoided;

The method has the following advantages: when the main data is updated, the main data is directly loaded and displayed without conversion, and the main data can be directly displayed by replacing files;

The advantages are four: and the more optimized loading, namely rendering mode, is operated in the UE engine, so that the use efficiency is improved.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention. The scope of applicability of the present invention is defined by the appended claims and equivalents thereof.

Claims (8)

1. A method of rendering native oblique photography OSGB data in a illusion engine, the method comprising:

step 100: providing a native oblique photography OSGB data file;

Step 200: loading a root LOD model, comprising: reading OSGB data files by using a C++ library provided by an OSG three-dimensional graphic engine, and analyzing files associated with a root LOD model;

Step 300: using Unreal Engine to load OSGB data files and generating index files of all files at the same time, wherein multithreading is adopted to perform file reading operation when loading OSGB data files;

Step 400: generating cache data for the loaded model; and

Step 500: integrating the loaded data, rendering with Unreal Engine,

The rendering method controls the use peak value of the whole memory and the video memory when loading OSGB data files.

2. The method of rendering native oblique photography OSGB data in a illusion engine of claim 1, wherein:

in step 200, the total number of root LOD models is calculated, and if the total number of root LOD models is greater than 100, model merging and face reduction processing is performed to reduce the total number of root LOD models.

3. The method of rendering native oblique photography OSGB data in a illusion engine as claimed in claim 2, wherein:

in step 300, the index file is stored while the OSGB data files are loaded, storing the parent-child file relationships for all files.

4. The method of rendering native oblique photography OSGB data in a illusion engine as claimed in claim 3, wherein:

the rendering method further includes: the index file is read when the OSGB data file is again loaded using Unreal Engine.

5. The method of claim 4, wherein the native oblique photography OSGB data is rendered in a illusion engine:

in step 400, the data within OSGB data files is stored as data suitable for Unreal Engine reading.

6. The method of rendering native oblique photography OSGB data in a illusion engine as claimed in claim 5, wherein:

The data suitable for Unreal Engine reads includes vertices, order of connection, texture map coordinates, maps, and mesh levels.

7. The method of claim 6, wherein the native oblique photography OSGB data is rendered in a illusion engine:

the rendering method further includes: limit verification is performed during loading OSGB of the data file, so that the condition that a collision peak crashes in the continuous loading and unloading process can be avoided.

8. The method of rendering native oblique photography OSGB data in a illusion engine as claimed in claim 7, wherein:

in the rendering method, the OSGB data file is directly loaded OSGB data file using Unreal Engine without format conversion.