A Virtual Reality Study on Santa Maria Crater on Mars

Jue Wang* and Keith J. Bennett

Department of Earth and Planetary Sciences, Washington University in St. Louis

ABSTRACT

This poster presents a study of virtual reality on selected sites on Mars. A Virtual Astronaut (VA) is created as an interactive virtual 3D environment for the planetary science community to support the Mars Exploration Rover (MER) mission. A prototype study was conducted based on orbital and Opportunity rover data covering Santa Maria Crater in Meridiani Planum. The prototype VA provides dynamic visual representations of the imaging, compositional, and mineralogical data for the rover operations. It lets one navigate through the scene and interact with the environment, such as viewing in-situ observations, feature measurement, and an animation of rover drives. The system is optimized based on a set of performance tests and user feedbacks.

Keywords: virtual astronaut, Mars surface, Unity, data fusion, navigation.

1 INTRODUCTION

NASA has been collecting immense store of digital images and other data for Mars from a number of successful orbital and landed missions. Due to the high cost and the unfriendly Mars environment, a manned mission to Mars is not expected in the coming decades. Therefore, building a virtual reality (VR) system for Mars using remote sensing data without actually sending human being there is important to help study the environment and evolution of this planet.

A variety of high-quality VR tools have been built that work with planetary image data sets. Examples of these tools include Mars in Google Earth, Microsoft's WorldWide Telescope (WWT), NASA World Wind from NASA AMES Research Center, and Exploration Guides to Gale Crater and Spirit's Journey that were developed as part of NASA/JPL/CalTech's outreach program [1]. These tools tend to either focus on orbiter or ground-based data, but do not combine both types of data.

A Virtual Astronaut (VA, [2]) has been developed for scientific exploration at the Geosciences Node of NASA’s Planetary Data System (PDS). The major objective of the VA is to develop a precise, highly-detailed, scientifically accurate 3D virtual reality environment that allows users to not only view observations made by a rover from the rover's perspective, but also allows users to view the scene and data from any perspective they want. In effect, the VA allows scientists to view a location of another planet in a manner similar to the way geologists would investigate the area if they were actually present there. The VA tool also combines images and topographic data obtained from orbital spacecraft with the high quality rover-based observations from the Mars Exploration Rover (MER) mission to provide a regional context to the area being investigated by the rover. The VA is targeted at the planetary science community and is designed to run as a desktop application or within a web browser.

2 THE VIRTUAL ASTRONAUT

2.1 What is the Virtual Astronaut

The VA is an interactive 3D environment which builds a world consisting of multiple objects for the visualization and interactions. As shown in Figure 1, the world created a scene with multiple image mosaics overlain on a digital elevation model (DEM). An object such as a rover model is placed on top of the surface terrains. The VA allows one to observe the Martian landscape, examine data collected and interact with a virtual MER rover.

Figure 1: User interface of the VA (reproduced from [2]). HiRISE

(High Resolution Imaging Science Experiment) data was

acquired from the Mars Reconnaissance Orbiter (MRO)

mission. Ground data includes Pancam (Panoramic Camera)

and Navcam (Navigation Camera) images taken by the MER

Rover.

2.2 Building the VA system

The VA was built on the Unity3D Game Engine and development environment (Version 3.4). Unity runs on Microsoft Windows and Mac OS X. Figure 2 shows the process for building the VA for a region of interest. Multiple orbital and surface data sets obtained from the NASA’s PDS or third parties are pre-processed to build a VA data model using a combination of tools. The VA data model includes a texture model, which is a 3D model of the surface with texture derived from image mosaics, animation paths, and a rover model. A set of world description files (WDFs) are created to describe the objects of a VA data model. This data pre-processing is the key step of generating a specific instance of the VA. Once generated, the VA data model and WDFs are loaded into a Unity3D-based virtual environment. A set of in-house tools and procedures have been developed for visualization and interactive functions within the VA, supplementing the basic modules and functions provided by Unity. These include visualization, navigation and interactive functions that evolved based on user feedbacks. The final application is published as a desktop application and on the web.

* wang@wunder.wustl.edu

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IEEE Virtual Reality 201316 - 20 March, Orlando, FL, USA978-1-4673-4796-9/13/$31.00 ©2013 IEEE

Figure 2: General approach used to build the Virtual Astronaut

(reproduced from [2]).

2.3 System Functions

The VA supports navigation through the virtual environment with various controls including a mouse, keyboard shortcuts, and a gamepad. The VA provides three modes: walk, drive, and target. Each mode gives you a unique viewpoint to investigate the Martian surface. The walk mode allows one to simulate freely along moving any direction around the terrain and to look left, right, up and down with adjustable viewpoint. The drive mode simulates a rover driving along the actual traverse taken by Opportunity. The target mode lets a rover directly jump to a surface target with in-situ observations. Additional tools are provided to make measurements, adjust the contrast of the scene, and change the terrain. The following figures give some screen shots of user scenarios with the VA.

a) Walk mode b) Target mode

c) Measurement tool d) High-resolution surface textures

Figure 3: User interface and example functions of the Virtual

Astronaut (reproduced from [2]).

3 SYSTEM DEVELOPMENT AND OPTIMIZATION

3.1 User-driven Development

The VA is developed based on user inputs and feedbacks. The survey of user requirements is an important factor designing and building the VA. In the initial design stage, lots of discussions were carried out with the students and staff working at the Department of Earth and Planetary Sciences at Washington University in St. Louis (WUSTL). These potential users gave feedback about the most useful functions they would like to see in the VA. These discussions lead to the development of interactive functions such as animation control of rover drives, visualizations of in-situ observations, and measurement of the size of features.

Before release, the system was evaluated by the target planetary scientist audiences. Besides the WUSTL users, it was peer reviewed by external science users and demonstrated before a dozen of scientists and specialists during conferences or meetings. The potential users gave experiences with scene controls and viewpoint controls for navigation through the scene. They tested function controls based on menus or icons. They also provided pros and cons for the fly mode and walk mode for the navigation.

Several VA functions that were prototyped and evaluated with user testing were not put into the final version due to the user confusion or complexity of a function. The evaluations and feedbacks resulted in a better tool for the audience.

3.2 Test and Optimization

System interoperability was also tested using different machines. The system was optimized based on the test results and user feedbacks.

3.2.1 Loading Time

The web based loading time is an important factor to evaluate system performance. Extensive tests were carried on the VA program at various platforms. Test statistics showed the loading speed mostly depended on the VA package size, the quality of the graphics card, graphics memory, computer RAM, and internet speed. With the same internet condition, package size matters more than all the other parameters. When the internet and the package size (e.g., ~150MB) are fixed, those machines that failed to load the VA program were older PCs with a poor graphics card (integrated card) or lower RAM (e.g., 512MB RAM).

3.2.2 Decrease Package Size

In order to run the VA on a large variety of computers, the package size was decreased by reducing the rover model, shrinking the coverage of the study area, resampling the resolutions of the DEMs, and using multiple levels of details for the texture model. Resampling the 3D DEM points to a lower resolution will cause the loss of terrain details. There is no fixed answer on which is the best resolution to use. This is decided by the study object and the tests and experiences. When the size of exported VA package was reduced to ~60MB, most of the test machines except some pretty old Pentium®4 computer (1.70GHz with 512 MB RAM) launched the VA within 1 minute.

In general, the released VA version 1 runs in most standard web browsers on Windows and Mac OS X computers with at least 2 GB of RAM, preferably with dedicated video memory. The Unity Web Player plug-in is required to be installed before running the VA. We did not find performance differences among various web browsers, such as Firefox, IE, and Google Chrome.

4 CONCLUSION

This poster introduces a prototype VA at Santa Maria Crater and its system development and optimization (http://va.rsl.wustl.edu/). The study demonstrates a cost-effective VR system built with the free Unity3D game engine software.

ACKNOWLEDGMENTS

This research was supported through funding provided by NASA’s PDS Geosciences Node. The authors wish to thank all of the colleagues working at the Geosciences Node for data archiving and valuable comments. We would like to thank the Geosciences Node Advisory Group for their valuable feedback and comments. Special thanks are given to OSU Mapping and GIS Laboratory, Dr. Wes A. Watters from Cornell and Stereo-Pipeline for the valuable data they provided for Santa Maria Crater.

REFERENCES

[1] Explore Mars! - NASA Jet Propulsion Laboratory. Available online:

http://mars.jpl.nasa.gov/explore/ (accessed on 19 December 2012).

[2] J. Wang, et al. Virtual Astronaut for scientific visualization - a

prototype for Santa Maria Crater on Mars. Future Internet.

4(4):1049-1068, 2012.

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