Digital Molecular Matter: Realistic material damage for military training simulations using real-time Finite Element Analysis

Digital Molecular Matter: Realistic material damage for military training simulations using real-time Finite Element Analysis

2Depicting material damage in military simulations has traditionally been a labor-intensive and expensive proposition. Now a new technology called Digital Molecular Matter (DMM), in conjunction with real-time Finite Element Analysis (FEA), promises to drastically improve simulation realism while reducing development time and cost.

Preparing war fighters for military engagement is both extremely important and extremely complex. The rules of engagement have changed over the years as battle lines are not always clearly defined. Today's war fighters are not trained simply to overtake the enemy. They must be aware of civilians caught in the proverbial crossfire of war. They must strive to achieve the goals defined for specific operations, minimizing any collateral damage that might come about.

Realistic training simulations depicting battlefield damage can help today's military achieve these goals, and that's where designers and developers come in. They must seek out new technologies that enable the creation of more realistic simulations. They must also be agile in adapting simulations to the shifting requirements of the moment.

Demand for increasingly realistic simulations - combined with shortened development timelines - is creating tremendous challenges for military simulation designers, developers, and managers. A new technology called (DMM) uses real-time physical modeling to address these challenges, producing more realistic simulations while meeting rapid design-to-delivery requirements.

The problem with art swapping

Recent advances in simulation platform technology allow for the rendering of highly realistic scenes; however, they do nothing to improve the kinetic realism that is just as important, if not more, than the visual realism - especially in military simulations. Stated another way, objects in the simulation need to look good, but they must also move and behave as realistically as they look.

Military simulations today rely heavily on art swaps or real-time substitutions of art assets to deform and break objects. When a projectile strikes a concrete wall, a script is run to show the wall crumbling. To create this effect in a simulation, artists have to draw hundreds of individual frames to show the slightest bit of motion or movement.

This approach limits an object's behaviors while greatly increasing the effort and time required to develop the simulation. A breaking pane of glass, for example, will always break the same way regardless of the simulated forces acting against it. Should a simulation require a change of material, such as the addition of bullet-resistant glass, new art assets need to be created and scripted to depict the new behavior. The time required to produce art swaps to depict kinetic effects drives up the cost of simulation development and can make the cost of updating an existing simulation prohibitive.

In an effort to improve kinetic fidelity, many simulations incorporate Rigid Body Dynamics (RBD) systems with art swapping to generate emergent behaviors. This approach has several disadvantages. Unconstrained emergent behaviors tend to produce unintended consequences and side effects, especially as the number of interactions between objects increases. And RBD is a very limited way of representing the physical properties of simulation objects. Simulation developers using RBD have only 10 variables to describe very complex materials: 3 translations, 3 rotations, mass, inertia, dampening, and coefficient of restitution (bounciness).

If simulation developers have any hope of meeting customer expectations going forward, they need a new approach that provides greater freedom to define and describe kinetic properties.

FEA provides thousands of degrees of freedom

The most promising approach to kinetic fidelity is to utilize Finite Element Analysis (FEA) in . Using FEA, a solid object is divided into constituent subparts, or elements. Stresses applied to the object as a whole are interpreted as stresses to the individual elements. The result is a more granular and realistic view of how an object reacts to stress.

Offline FEA simulations have been used in the manufacturing industry for many years. FEA simulations are used to test and refine designs before the prototype phase of production - reducing the number of prototypes required, improving time-to-market, and reducing costs. Figure 1 shows how a car deforms using Finite Element Analysis.

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Figure 1
(Click graphic to zoom by 2.5x)

FEA utilizes a mesh to discretize a solid object into a set of discrete elements. Calculations can then be applied to these elements to visualize where objects bend and twist and reveal the distribution of stresses and displacements. Utilized in a real-time simulation environment, FEA allows for a vastly more realistic representation of a simulated material. Armed with FEA in real time, simulation developers have thousands of degrees of freedom in describing how each discrete element can move and interact with the simulation environment. Moreover, the properties of these elements can be set to accurately behave like real-life materials: concrete crumbles; metal bends, deforms, and tears; and wood breaks and splinters. The result is kinetic fidelity never before seen in real-time simulations.

Materials can react in entirely new ways each time the user engages in the simulation. So when a tank drives through a brick wall at different angles, the wall will crumble differently each time. What is more, art objects developed with an FEA mesh are created once, and their fracture and deformation behavior is determined by their material properties and rendered in real time - eliminating the need for art swapping.

Not only is the software advancing, but processor technology has caught up. Modern processors can now run finite element-based simulations in real time.

Using real-time FEA technology, simulation developers can vastly improve the visual and kinetic fidelity of their simulations while reducing asset creation time and cost. Simulations no longer need be scripted scenarios, and time-to-deployment is exponentially faster.

Digital Molecular Matter facilitates FEA

DMM is a real-time implementation of finite element physics. DMM technology is implemented as a real-time engine subsystem that runs independently of the primary simulation system; it also includes the tools required to convert ordinary meshes created by artists into finite element volumetric meshes.

A key advantage of DMM is the ability to add FEA effects to new objects as they are created or to existing objects for enhanced capability. With minimal effort, simulation developers can leverage their existing investments by adding DMM capability to legacy simulations.

Originally conceived by Pixelux Entertainment for the gaming industry, DMM attracted the attention of LucasArts, who wanted to deliver state-of-the-art gameplay technology in its upcoming Star Wars and Indiana Jones video games while reducing production costs. In late 2005, Pixelux began working in partnership with LucasArts to develop and refine DMM into an artist-friendly technology that could deliver the promise of finite element physics.

Pixelux subsequently partnered with (OIS) to adapt DMM to the military and aerospace simulation market. The resulting product, DMMfx, was introduced at the I/ITSEC 2007 trade conference.

DMMfx provides the means to deploy military simulations with realistic deformation and fracture of materials. Wood twists, splinters, and breaks like real wood; metal deforms, bends, and tears; and glass shatters like glass. Damage such as buckling, tearing, and fracture, along with collateral effects, occur in expected ways. Simulations perform with unpredictability and realism, making them more effective. Figure 2 shows a tank breaking through wooden fences in a simulation using DMMfx.

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Figure 2
(Click graphic to zoom by 2.5x)

DMM architecture and implementation

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Figure 3
(Click graphic to zoom)

The DMM subsystem runs independently of the primary simulation engine, exchanging information about forces being applied to a scene, determining whether objects are being kinematically driven, as well as other physical interactions. Force feedback is a natural result of these interactions and can be used to generate additional visual effects and realistic sounds resulting from collisions and distortions.

The process for adding these effects is straightforward, utilizing techniques familiar to simulation artists. Artists start with a surface mesh for a new or existing object. This mesh is then used as the basis for a tetrahedral "cage." This cage is then used to create a tetrahedral mesh of the volume of the object. Finally, if the object is breakable, the mesh has to be clipped against the surface mesh and have internal faces added that will be visible when the object breaks. Figure 3 shows a typical DMM workflow.

In addition, DMM also implements a visual enhancement called splinter geometry. Splinter geometry allows for the visually correct disintegration of objects that are naturally made up of component pieces such as wood, brick walls, and stone buildings. Splinter technology provides an increase in realism by fracturing objects in ways that appear more complex, without having to create a denser mesh. Figure 4 shows a timber being twisted and splintering.

DMM also provides the ability to optimize scene performance by compressing objects within a scene, or by freezing inactive portions of a scene to relieve the system from having to simulate unused elements. Meshes not in live use are made dormant until they are needed.

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Figure 4
(Click graphic to zoom by 2.1x)

Better simulations, better results

Improving military simulations to realistically depict material damage is crucial to the success of today's war fighters. Going forward, military simulation developers cannot afford to continue to rely on art swaps to depict the fracture and deformation of objects, so a new approach is needed. Improvements in simulation platform technology make the implementation of real-time Finite Element Analysis through Digital Molecular Matter a practical solution. Using this approach, military simulation managers, designers, and developers can deploy more kinetically realistic simulations while reducing development time and cost. The result is a better-trained war fighter capable of meeting the demands of the battlefield today and tomorrow - while reducing collateral damage.

Steve Griffith is the director of business development for physical modeling and simulation at Objective Interface Systems. He has more than 20 years of business development, engineering, and management experience in the software industry. He can be contacted at steve.griffith@ois.com.

Objective Interface Systems
703-295-6500
www.ois.com