Visualizing perceived spatial data quality of 3D objects within virtual globes

Virtual globes(VGs)allow Internet users to view geographic data of heterogeneous quality created by other users.This article presents a new approach for collecting and visualizing information about the perceived quality of 3D data in VGs.It aims atimproving users’awareness of the qualityof 3D objects.Instead of relying onthe existing metadata or on formal accuracy assessments that are often impossible in practice,we propose a crowd-sourced quality recommender system based on the five-star visualization method successful in other types of Web applications.Four alternative five-star visualizations were implemented in a Google Earth-based prototype and tested through a formal user evaluation.These tests helped identifying the most effective method for a 3D environment.Results indicate that while most websites use a visualization approach that shows a‘number of stars’,this method was the least preferred by participants.Instead,participants ranked the‘number within a star’method highest as it allowed reducing the visual clutter in urban settings,suggesting that 3D environments such as VGs require different designapproachesthan2Dornon-geographicapplications.Resultsalsoconfirmed that expert and non-expert users in geographic data share similar preferences for the most and least preferred visualization methods.

Three-dimensional trees for virtual globes

One of the problems in virtual globes technologies is the real-time representation of vegetal species.In forest or garden representations,the low detailed plants produce a lack of realism.Efficient techniques are required to achieve accurate interactive visualisation due to the great number of polygons the vegetal species have.This article presents a multi-resolution model based on a geometric representation of vegetal species that allows the application to perform the progressive transmission of the model,that is,the transmission of a simple representation followed by successive refinements of it.It has a hardware-oriented design in order to obtain interactive frame rates.The geometric data of the objects are stored in the graphics processing unit and,moreover,the change from one approximation to another is obtained by performing mathematical calcula-tions in this graphics hardware.The multi-resolution model presented here enables instancing:as many vegetal species as desired can be rendered with different levels of detail,while all of them are accessing the same geometric data.This model has been used to build a real-time representation of a not imaginary scenario.

Implementation of a 3D WebGIS for Dynamic Geo-Referencing of 3D Tiles on the Virtual Globe

Needs for real-time interactive visualization of 3D Tiles for massive 3D content on the web-based virtual globe is rapidly increasing, and to achieve this goal, 3D Tiles needs to be correctly geo-referenced to other geospatial data on a web-based virtual globe. It is possible to generate 3D Tiles from different kinds of spatial data through various software tools. However, due to various factors the 3D Tile datasets are often poorly or not at all geo-referenced. To tackle this issue, we propose a new 3D WebGIS framework that facilitates dynamic geo-referencing 3D Tiles on the CesiumJS virtual globe.

Editing Vector Graphics in the Virtual Simulation Environment

We present a method to represent multi-resolution vector graphics such as road networks or railway networks in virtual environment. These vector data can be interactively edited and the landscape and be explored in real time at any altitude from flight view to car view. We design a context-focused vector description of linear can areal features, with associated customized definition painter to specify their appearance （color and material） and their display mode （detailed mode or simplified mode）. There are some special problems in drawing vector graphics in virtual environment. Floating-point round-off error appear when we use a low view point to observe the scene, and it leads to scene jittering. Drawing 3D wide lines turns into a problem on 3D terrain. We design a view-based self-adaptive interpolation algorithm and an offset line generating algorithm to solve it. Our results show high performance with good visual quality.

Graphics processing unit-based dynamic volume rendering for typhoons on a virtual globe

Typhoons are usually accompanied by strong winds,heavy rain,storm surges and other disastrous events,and they are the most severe weather phenomena in the western part of the North Pacific Ocean.Visualisation is a key technology for analysing and presenting climate simulations and observations together with related social and ecological data.Virtual globes are a logical platform for visualising such geospatial data via the Internet.To implement interactive visualisation of typhoon data within virtual globes,this study provides a 3D texture-mapping algorithm to render volume textures on a globe.In addition,a systematic framework is proposed in which a hierarchical octree-based multiresolution data structure is implemented to organise the large volume dataset,and a graphics processing unit-based dynamic interpolation approach is proposed to obtain a smooth effect.Finally,the structure is combined with a level of detail strategy to enable the rendering of dynamic volumetric data at an acceptable interactive frame rate.To demonstrate the capabilities of this framework,data for a simulated typhoon event were rendered in World Wind,an open-source virtual globe.The experimental results demonstrate that the application of the proposed strategies can result in an interactive visualisation performance that renders typhoon data on virtual globes.

A binocular parallel rendering method for VR globes

The scene-rendering mechanism based on binocular vision is one of the key techniques for the VR globe to achieve immersion-type visualization of global 3D scenes.However,this special rendering mechanism also requires that the 3D scene is continuously drawn twice within one frame,which significantly affects the rendering efficiency of VR globes.Therefore,we propose a binocular parallel rendering method.This method first improves the current rendering process of VR globes by assigning the rendering tasks for the left and right camera of VR to be processed on different CPU cores,thereby achieving parallel rendering of binocular scenes.Second,due to the problem of inconsistent resolution of binocular scenes caused by different viewpoints for the left and right cameras,we propose a resolution synchronize algorithm.this algorithm conducts realtime synchronization on the resolution of scene in the rendering process and thus avoids the problem of erroneous binocular stereo matching.Finally,we validate the effectiveness of the method in this paper through experiments.The results of experiments indicate that while the method in this paper can ensure the consistency of binocular scene resolution,it can decrease the frame time of VR globes by approximately 27%on average.

GPU ray casting method for visualizing 3D pipelines in a virtual globe

Pipelines are an important part of urban infrastructure development.As part of a virtual globe(VG),the high-efficiency and high-quality visualization of 3D large-scale and high-density urban pipelines is of great importance.This paper proposes a GPU-based pipeline ray casting method for the visualization of urban-scale pipelines in the framework of a VG.The method involves the initial partitioning of the pipeline data into tiles,based on the relationship between the pipeline layer scale and the discrete global grid system(DGGSs).The pipeline centerline in each tile is then segmented and encoded,and a coarser pipeline bounding volume is subsequently constructed using a geometry shader.Finally,the fine 3D pipeline is rendered using a pixel shader.The results of the experimental implementation of the proposed method show that it satisfies the requirements for the multiscale visualization of pipelines in a VG.Moreover,compared with the traditional polygon-based method,the method facilitates a 20%increase in rendering frame rate for the same pixel level accuracy display effect.It also enables the visualization of the thickness of the 3D pipeline without any obvious effect on the rendering efficiency。

Virtual globe-based integration and sharing service method of GeoSpatial Information

How to integrate and disseminate globally distributed multi-source and heterogeneous spatial information is an open problem in integration and sharing service of geographic information. Here we propose a new service architecture suitable for integra- tion and sharing of distributed multi-source geographic information. We also propose a global virtual pyramid model, which can be applied in 3D virtual globes. In view of the difficulty of web multi-node geographic information sharing service, we propose a web multi-node service aggregation method, integrated in our autonomously developed virtual globe platform Geo- Globe and introduced in the National Platform for Common GeoSpatial Information Services named ＂T1ANDITU＂. It achieves 2D and 3D integration for geographic information service.

A virtual globe-based time-critical adaptive visualization method for 3D city models

3D city models,which are important items of content on the virtual globe,are characterized by complicated structures and large amounts of data.These factors make the visualization of 3D city models highly dependent upon the performance of computer hardware.Thus,achieving the efficient rendering of 3D city models using different hardware performance levels represents one of the key problems currently facing researchers.This paper proposes a time-critical adaptive visualization method that first estimates the possible rendering time for each model according to the data structure of the model in addition to the CPU/GPU performance of the computer.It then dynamically adjusts the rendering level for each model based on the results of an estimation of the rendering time to ensure that the final scene can be completed within a given time.To verify the effectiveness and flexibility of this method,it is applied using different computers.The results show that the adaptive visualization method presented in this paper not only can adapt to computers with different levels of performances but also demonstrates an obvious improvement in the time estimation precision,visual effects,and optimization speed relative to existing adaptive visualization methods.

Shaping digital earth applications through open innovation - setting the scene for a digital earth living lab

Science and policy increasingly request for sustainable development and growth.Similarly,Digital Earth undergoes a paradigm shift to an open platform that actively supports user engagement.While the public becomes able to contribute new content,we recognize a gap in user-driven validation,feedback and requirements capture,and innovative application development.Rather than defining Digital Earth applications top down,we see a need for methods and tools that will help building applications bottom up and driven by community needs.These should include a technology toolbox of geospatial and environ-mental enablers,which allow to access functional building blocks and content in multiple ways,but-equally important-enable the collaboration within partially unknown stakeholder networks.The validation and testing in real-life scenarios will be a central requirement when approaching the Digital Earth 2020 goals,which were articulated recently.We particularly argue to follow a Living Lab approach for co-creation and awareness rising in relation to environmental and geospatial matters.We explain why and how such a Digital Earth Living Lab could lead to a sustainable approach for developing,deploying,and using Digital Earth applications and suggest a paradigm shift for Virtual Globes becoming forums for research and innovation.

Fast registration of multisource three-dimensional city models in GeoGlobe

We address the registration problem of multisource three-dimensional(3D)human-made buildings with remote sensing images and the earth’s surface in the context of virtual globes.Challenges include fast transformation of 3D coordinates with different reference systems as well as the efficient use of original model information for rigorous and accurate model registration.This paper introduces a novel fast and scalable registration approach that can establish correspondences between heterogeneous external 3D city models and images/terrain surfaces of virtual globes in an efficient and accurate manner.The approach utilizes the projected 3D feature information of 3D city models to develop robust coordinate transformation and reliable model registration methods.The proposed approach builds a solid foundation for the fusion of multisource geospatial data in a united virtual globe reference framework.We report experimental results of online registration tasks for up to over 13K buildings in an integrated 3D virtual globe platform,namely,GeoGlobe.

A multistage collaborative 3D GIS to support public participation

This paper presents a collaborative 3D GIS to support public participation.Realizing that public-involved decision-making is often a multistage process,the proposed system is designed to provide coherent support for collaborations in the different stages.We differentiate ubiquitous participation and intensive participation and identify their suitable application stages.The proposed system,then,supports both of the two types of participation by providing synchronous and asynchronous collabora-tion functionalities.Applying the concept of Digital Earth,the proposed system also features a virtual globe-based user interface.Such an interface integrates a variety of data,functions,and services into a unified virtual environment which is delivered to both experts and public participants through the Internet.The system has been designed as a general software framework and can be tailored for specific projects.In this study,we demonstrate it using a scene modeling case and provide a preliminary evaluation toward its usability.