What is the Difference Between Animation and Simulation?

'What Is' type questions related to highway safety, accident reconstruction and vehicle simulation
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What is the Difference Between Animation and Simulation?

Post by brian »

Q: What is the difference between animation and simulation?
A: This is a frequently asked question particularly with the current capabilities of computers and animation. In accident reconstruction,
  • Animation is often used to illustrate an opinion.
    • Animations generally use spline fit techniques to visually match movements of vehicles. Animation by itself does not test whether the movements and responses are physically possible, meaning whether or not they obey Newton’s Laws of Motion
  • Simulation is used in accident reconstruction to test and refine an opinion.
    • Simulations are mathematical models which attempt to apply and follow Newton’s laws of Motion. Simulations can be used as the basis for an Animation meaning the mathematically simulated motion can be used in an animation to move the objects (for example, to move vehicles colliding, etc).
CAUTION: Simulations and Animations can also be used inappropriately!
  • The inputs should be fully revealed and checked.
    • See 3D or Not 3D for a presentation of what you need to request when faced with a Simulation or Animation.
    For simulations you also need to verify if the model has been tested and validated and if the type of vehicle movement or collision interaction are consistent with the validations. All too often we find ‘experts’ misusing simulation models. For example see our discussion on the ATB simulation model and our discussion 3D or Not 3D for some related discussion on validation and simulation models.
Some additional information:
  • From the web Animation
    • "is the rapid display of a sequence of images of 2-D or 3-D artwork or model positions in order to create an illusion of movement. It is an optical illusion of motion due to the phenomenon of persistence of vision, and can be created and demonstrated in a number of ways. The most common method of presenting animation is as a motion picture or video program, although several other forms of presenting animation also exist".
    From the web Simulation
    • "is the imitation of some real thing, state of affairs, or process. The act of simulating something generally entails representing certain key characteristics or behaviors of a selected physical or abstract system. Simulation is used in many contexts, including the modeling of natural systems or human systems in order to gain insight into their functioning.[1] Other contexts include simulation of technology for performance optimization, safety engineering, testing, training and education. Simulation can be used to show the eventual real effects of alternative conditions and courses of action. Key issues in simulation include acquisition of valid source information about the relevant selection of key characteristics and behaviours, the use of simplifying approximations and assumptions within the simulation, and fidelity and validity of the simulation outcomes".
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Re: What is the Difference Between Animation and Simulation?

Post by MSI »

Aug 2019: Another reason to request/demand the detailed positions and orientations of any and all vehicles displayed in an animation/simulation:
  • When evaluated in detail does the acceleration/deceleration/cornering abilities of each vehicle displayed coincide with the actual performance capabilities of each vehicle?
  • And when you consider performance capabilities of a vehicle you need to consider the condition of the vehicle at the time of the collision since vehicles on the road can not perform in mint and/or "as new" condition.
    • When was the last tune up? how many miles on the vehicle?
  • During any collision(s) depicted in the video (animation or simulation) what are the accelerations and do they
    • coincide with a realistic collision interaction (if animation) or
    • are the simulation inputs proper?
      • stiffness of each vehicle,
      • if momentum based simulation is the "point of instantaneous momentum exchange" sensitive to minor changes which result in major changes in the results?
It is important and essential that the actual detailed time history of the positions and orientations depicted in the actual animations/simulations be available.
  • Detailed should mean 0.03 second step size or smaller
    • animations are 30 fps or 0.03 step size so that should be easy'.
      • Animations use spline fit interpolation so key frame positions may be cruder however the displayed positions and orientations for each frame (as interpolated by the software) is calculated and needs to be revealed.
    • Simulations should be at that or less: 0.01 sec step size or 0.001 step size
if the detailed input and output information is provided in the native file format for the software being used (for both simulation and/or animation) this will allow a proper analysis of the animation and/or simulation. It allows an expert to recreate the motions of the vehicle depicted in the video so then the expert can calculate detailed acceleration/deceleration, etc.
  • If merely an animation program, the inputs in electronic and paper format so it can be rerun (electronic) and loaded into a spreadsheet to manually calculate what the displayed performance and collision interaction(s) mean in physical terms.
  • If an animation of a simulation then both electronic and paper input and output files are required for BOTH to insure that the output data from the simulation was properly transposed to the animation program.
  • If a simulation program also created the animation then the inputs and outputs, in electronic and paper format, must be disclosed so any expect can check that the video is a proper representation of the simulation.
From SAE paper 980018, “Documenting Scientific Visualizations and Computer Animations used in Collision Reconstruction Presentations“:
  • “This paper has presented a proposed standard for documenting computer generated images, animations, scientific visualizations, etc. The basic standard is that any still images or videos should be documented such that any qualified analyst can reproduce them. This is the requirement for the scientific community in general and should be adopted in the crash reconstruction community. It is important to note that this standard does not refer to any method of generating these images or videos. There is no implication that any one method or any one program is superior to others. This standard addresses only the images and videos and does not address the analysis or opinions being expressed by analyst. However, the only way to fully understand the analysis being presented or discussed is to have the ability to duplicate the images or video being presented”
Please also see related topic: What files should be produced for Simulation and Animation
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