What files should be produced for Simulation and Animation

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MSI
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What files should be produced for Simulation and Animation

Post by MSI » Tue Dec 17, 2013 8:41 pm

Q: On another forum someone posted the question asking what files are required to be provided when you use a Computer Simulation or Animation in court?
A: In over 30 years in almost every state in the US, I have found for every situation where computer simulation OR animation is used by either side the complete input and output files must be disclosed or the computer results are not allowed.
It is our duty as reconstructionists to let our attorneys know that we need to provide and/or ask for the input/output files!
This is to allow verifying the results and insuring that ALL inputs have been disclosed
  • (i recall one where a 'hidden' ice patch was used in a simulation to allow the vehicle to travel farther than Sir Issac said was allowed. It wasn't printed in the 'input echo' and was discovered when the actual input file was loaded and the simulationb re-reun)
Items which should be required/provided if you or an opposing expert uses Computer Simulation or Animation:
  • Printed and in computer form (CD or diskette). (Printed output pages can be saved as text files and copied to a CD to save paper)
  • Most of the programs include options for outputs. The outputs should be set with ALL OPTIONS ON to obtain all the outputs and time history data, etc.
  • Request the program version, an indication of any add-ons or options used, etc.
  • If a video created, request all the files used to create the video: CAD files, Animation files, spreadsheet files, any and all notes, etc.
From '3-D' or not '3-D', THAT is the Question! here are some SAE papers:
  • 1999-01-0101 "Computer–Generated Trial Exhibits: A Post- Daubert Update"
  • 940920 "Case Studies in Animation Foundation"
  • 980018, "Documenting Scientific Visualizations and Computer Animations used in Collision Reconstruction Presentations"
    which includes as the Summary:
    • "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 accident 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 an 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"
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MSI
Site Admin
Posts: 1264
Joined: Thu Jun 18, 2009 12:37 pm

Re: What files should be produced for Simulation and Animation

Post by MSI » Thu Aug 22, 2019 2:35 pm

We have added to our thread on What is the Difference Between Animation and Simulation? the following which we repeat here for convenience related to what files should be produced:

Why 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”
Question? Comment? Please email forum@mchenrysoftware.com. Also see the McHenry Forum Index
Visit McHenrySoftware.com for technical information & software.
(c) McHenry Software, Inc ALL Rights Reserved.

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