Sunday, November 29, 2015

2015 HELP: A physics engine is not needed in OpenSim--Kayaker Magic

A physics engine is not needed--Kayaker Magic
Object movement can be scripted in the object.   

  • Watch on YouTube
  • Sorry for the audio problems. This is live capture.
  • Also, particles were were turned off for the first half hour 
  • and not fully implemented later, so the effects were not well shown.
  • Scripters don't need a physics engine to make a bullet go in a parabolic path.
  • We know how to script a parabolic path, even though it is "rocket science." 
  • We know how objects should behave under physics.
  • Kayaker got tired of trying to cope with various physics engines.
  • So he stopped using them and scripted the movement himself.
  • You can too.  Even if grids have a physics engine, you don't have to use it. 
  • (More after the break)

Metaverse events, current and upcoming

  • OSCC15:  Dec 5.
  • The Grand Finale Winners announcements for MachinimUWA VIII:  
  • Sunday 12/13 6AM SLT (note its AM!!) 


        Metaverse beginner help


        What is a Physics Engine good for?--Kayaker Magic

        People say that without physics, your Avatar would fall through the floor. Well, that still happens with a physics engine. I've even had it happen with Havok on SL. Watching the PhysX engine working on InWorldz I have come to the conclusion that it has a lot of special case code to prevent or recover from feet falling through the floor. Why not keep the special case code and throw out the physics engine?
        When avatars fly, it looks like physics is thrown out the window, don't need it there.
        People use physics to implement weapons. But developers and grid managers say tossing lots of physical bullets around puts a huge burden on the servers. They say it would be better if we used llCastRay to implement weapons without physics. llCastRay has its problems in OpenSim but I have found it adequate (barely) for scripting weapons without physics. So I still don't need a physics engine.
        People think that you can't have vehicles in virtual worlds without physics. I have successfully scripted dozens of vehicles that work without physics. When needed, I do my own physics calculations infrequently and interpolate between calculations with llSetKeyframedMotion. Many things, like fish swimming, don't behave in a very physical way and don't need any physics calculations. You may say you need the physics engine to make cars jump off ramps and fall through the air. But it is easy to calculate that parabola yourself, even though it may actually be “Rocket Science”.
        I occasionally see people building marble racecourses, bouncing prim mazes, gears that turn each other, or stacks of hundreds of prims that collapse under physics. These are fun for a minute, but they are not the things that the majority of people come to virtual worlds for. If balls didn't bounce right there would still be things to do here. We don't need a physics engine accurate enough to simulate the collapse of a skyscraper in an earthquake. We could make do with a much simplified physics engine.
        They say you need physics to prevent avatars from walking through walls and vehicles from passing through each other. Now this is something I would like the system to help me out with. All those non-physical vehicles I built will just pass through each other. But does it have to be the physics engine that does this for me? I don't need to have vehicles bounce off each other in a realistic physical way. In fact most physics engines over-react to physical vehicles colliding with each other and make them do weird things. Like flip over and jump 10 meters up in the air. If that is what physics engines do for me, having vehicles pass through each other is not so bad!  Instead, notify the scripts that a collision is happening and let them deal with it. Or just disable motion when it happens. So what I need is a Collision Engine, not a physics engine.
        These experiences have me thinking that the people developing new technology for Virtual Worlds should stop thinking that a physics engine is really necessary. Perhaps new virtual environments like HiFi never need to add one. If the scripting engines in these worlds is good enough, we can just write our own physics into only the objects that need it. I am guilty of wishing that every tree, every blade of grass in my worlds could have a script in it. This has gotten me in trouble in Kitely were the world load time gets slower the more scripts it has to start up. Perhaps newer environments like HiFi will be friendlier for scripters!

        The hypergrid WIP show

        The Hypergrid WIP Show.   Upcoming WIPs Dec. 13 - Location to be announced. WIPs are on 2nd and 4th Sundays from noon to 1pm PT. 
        The Hypergrid WIP is a one hour "show & tell" of works in progress or recently completed. All builders from beginner to pro are invited. Please come and take a few minutes to show us something you have built or are working on. This is all about community and sharing. And inspiration. And support. And fun! This is a hypergrid event. People from all grids are invited. 
        *** DETAILS FOR PRESENTERS *** If you are coming from another grid, put the item in your suitcase and it will come with you. If you come from a grid that doesn't use a suitcase folder, you may have to give the item to the event host to rez. It will be deleted from their inventory when we are done, but you may need to change permissions just to give it to her. 
        It's nice to bring a full perm notecard with a description of your object and a little background about how and why you built it. Some of our audience members cannot hear the voice chat. You will be added to the a group in order to rez. You will need to activate that group. 
        The show is in a casual "show and tell" format. You will rez your object and then say a few words about it. Tell us what inspired you or how you built it or maybe what you plan to do with it. The audience will probably ask a few questions. The time allotted to each presenter will depend on how many people show up, but you don't have to use all your time. 
        All kinds of creations are welcome. Prims, Mesh, Avatars, Scripts, Animations, and Images. 
        The grid owner has suggested that there will be less lag if large items are phantom. 
        The show lasts 1 hour exactly, but the sandbox remains open for folks to hang out.

        Previous Articles from the WIP show 

        News and Notes


          The Hypergrid WIP Show

          The Hypergrid WIP is a one hour "show & tell" of works in progress or recently completed. All builders from beginner to pro are invited.  Presentations are in voice and text.  For text presentations, best bring the text in a notecard and paste it into chat.  Voice presentations may be captured in video.  Stills and videos from the show may appear in this blog. 

          Next WIP show 

          • Next WIP show: TBD  
          • HG address below: paste into the World Map next to Find. Click Find, TP
          • II 
          • in Kitely: paste into Nav (top) bar of Firestorm, Enter.
          • hop:// II/68/369/22

            Previous Articles from the WIP show 

                Entertainment on the Hypergrid

                HG links-- depending on your interests

                • I publish about 6 days a week, skipping 1 or 2 days in midweek
                • For more on topics like this, circle Selby Evans in Google+ 
                • What do we do in Virtual Worlds? 
                • Search on page with Google Chrome: Ctrl+f, search bar upper right.
                • Google search this blog: Search bar, upper left--or:
                • Put at the end of the search terms 
                • What is Second Life?
                • Annotated screen shots made with Jing
                • All original content on this blog is Creative Commons License, attribution only. 
                • Second LifeLindenSLurl, and SL are trademarks of Linden Research Inc. 
                • This blog is not affiliated with Second Life or anything else. 
                • Ads are from Google.

                1 comment:

                Note: Only a member of this blog may post a comment.