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brucedjones

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About brucedjones

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  1. brucedjones

    Why NASA Switched from Unity to Blend4Web

    Title is a bit misleading since the article is just your speculation.   Also, I would think the reason is more likely to be "Someone else eventually got the contract who preferred blend4web"
  2. brucedjones

    Estimating Effort for Small Projects

    I prefer to follow Scotty's Law. Increase your best estimate by an order of magnitude, report that figure. The captain will be pleased when you take a day to do something you said would take a week :)
  3. brucedjones

    Towards a Simpler, Stiffer, and more Stable Spring

    h4tt3n, you would define the global timestep based on the limiting stiffness. That is, you would compute the eigen-frequency for all springs in your system, and base your global timestep on the maximum. If the stiffnesses are constant for all springs, you only ever have to do this once so its hardly impractical.     What you have done basically relies on the critical timestep. Look at the equations in the link again and you will see the critical stiffness is,   K_crit = 4m/(dt^2)   Which is suspiciously similar to the form of your coefficients in the equation that follows the "reintroducing coefficients" section, ie Cm/(dt^2) for the first term. Your formulation and guidance therefore sets the stiffness well below the critical stiffness for the chosen timestep.   I feel this article would benefit from a discussion of the critical timestep and how it relates to your work. Despite my comments I like the conceptual explanation of the coefficients relating to rigid and springy springs.   PS. Your quote from the YADE docs's refers to the case where timestep leads to very large displacements relative to the system size, your formulation would suffer problems in this case also.
  4. brucedjones

    Towards a Simpler, Stiffer, and more Stable Spring

      Your motivation for all this is flawed. This "unkown threshold" is actually a known threshold, the term that applies here is the critical timestep. You can compute the critical timestep from known quanitities of mass and stiffness. Further reading is found here (see the section for a general mass-spring system):   https://yade-dem.org/doc/formulation.html   Now in a game environment there are likely limitations on timestep. However it is very easy to do a "back of the napkin" calculation to see if a simple mass-spring system will work in your case.
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