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Question WriteGroups and ExportPhysicsWorld, BodySmoothing, et. al.

Discussion in 'Physics for ECS' started by Thygrrr, Apr 9, 2021.

  1. Thygrrr


    Sep 23, 2013
    I recently wrote a custom floating origin (and, in a way, camera centric rendering) system that replaces (pre-empts) TRSToLocalToWorldSystem by means of write groups, meaning that if an Entity has the FloatingPosition component, its LocalToWorld will be built by the FloatingToLocalToWorldSystem instead.

    Works like a charm! (big thank you to the folks in the floating origin thread!)

    Now, I face a minor (?) issue:
    • if there's an Entity with a PhysicsBodySmoothing component, the system doesn't pick that one up, regardless of whether it has a TagExcludePhysics component or not, or whether the smoothing has been disabled via the component's internal state.
    Question, if I either write my own physics or somehow use DOTS physics for the movement in the floating origin space: How do I make the "WriteGroup'ness" of a third component like PhysicsBodySmoothing not affect my own TRStoLTW system, especially assuming I would very much like to use smoothing, and write the position/time values in my own system?

    Can I somehow write a special variant of that system that works like the system that applies the interpolation; and where do I put it / how does its query and FilterWriteGroup options differ?

    A possible alternative is writing a completely separate physics integrator for "open space" versus "bubble space" (where classic short range physics apply), and for visibility checks I'd be needing build a sensible BVH, for which I don't find enough documentation to build and query my own. Using the existing physics world for this is considerably easier, even though I probably have to create some occluder entities that I move around, or I'd face precision issues.
  2. milos85miki


    Nov 29, 2019
    Here's what you could try:
    1. Disable SmoothRigidBodiesGraphicalMotion system (
    World.GetOrCreateSystem<SmoothRigidBodiesGraphicalMotion>().Enabled = false; 
    ) and write your own system for smoothing
    2. Use a new component instead of PhysicsGraphicalSmoothing. This is a bigger chunk of work, since you'd have to replace the component during conversion and then write new systems that copy physics velocity to the new component and perform smoothing

    Please let me know how it goes.