Video Tutorial: Density, Friction, Bounciness

ArmellineArmelline Member, PRO Posts: 5,364

A quick look at these three physics attributes that can easily be very confusing!

It's 3am so sorry for the rough editing!

Attached to this post is the project file used.

Comments

  • SocksSocks London, UK.Member Posts: 12,822
    edited October 2015

    Great !

    Like the 2am tutorials brand :smile:

  • GameAlchemistGameAlchemist Member Posts: 106

    Thanks for this. It helps clear the fundamentals of how these three physics work.

  • MentalDonkeyGamesMentalDonkeyGames Member Posts: 1,276

    Nice and clear video, as always.

    Mental Donkey Games
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  • RThurmanRThurman Member, Sous Chef, PRO Posts: 2,880

    Thanks for this tutorial. I now have a much better intuition about how density interacts with an actor's size.

  • KnightStarKnightStar Member Posts: 162

    Great Tutorial.. I didn't realize that an object's Density was also affected by the object's size..

    Learn something new every day.. :smiley:

    -- J

  • ArmellineArmelline Member, PRO Posts: 5,364

    @KnightStar said:
    Great Tutorial.. I didn't realize that an object's Density was also affected by the object's size..

    It's the mass that's affected by the size, based on the density. But yes, size has an impact!

    Density = Mass / Volume

    So if the density is 1, and the mass is 10kg, you can work out how big it is. And if you know the density and the volume, you can work out the mass.

    The end result, though, is the bigger an object is the heavier and more difficult to move it is, and how difficult two same-sized objects are to move will depend on their density!

    You can have a wooden block and a gold block of the same size, but since the gold block has a much higher density, it will be heavier and harder to move.

    Glad people are enjoying the video, though!

    I need to pair up with a graphics guy who can do some diagrams and examples to show!

  • grishlockgrishlock Member, PRO Posts: 32

    @Armelline
    The size of the object and it's density affects the mass of the object. Does the friction depend on the size of the object? A larger surface with the same friction as a smaller surface should slow down an object sooner.

  • Braydon_SFXBraydon_SFX Member, Sous Chef, Bowlboy Sidekick Posts: 9,273

    Great stuff, @Armelline - I learned something new as well!

  • ArmellineArmelline Member, PRO Posts: 5,364

    @grishlock said:
    Armelline
    The size of the object and it's density affects the mass of the object. Does the friction depend on the size of the object? A larger surface with the same friction as a smaller surface should slow down an object sooner.

    As far as I know, friction is defined purely by the friction attribute. The assumption should be that no matter how big and heavy an object is, it remains super slippery unless the friction is set to make it less so. One of the staff will need to confirm that, though.

  • Thunder_ChildThunder_Child Member Posts: 2,343

    Excellent these are great fundementals I still dont have down yet !!

  • SocksSocks London, UK.Member Posts: 12,822
    edited October 2015

    @Armelline said:
    As far as I know, friction is defined purely by the friction attribute. The assumption should be that no matter how big and heavy an object is, it remains super slippery unless the friction is set to make it less so. One of the staff will need to confirm that, though.

    One of Friction's more important aspects is that - when in collision with another object - an actor with friction will be slowed down . . . . that much seems obvious enough . . . . but in lots of gaming situations we want an object to bounce off a surface and for its angle of reflection to match the angle of incidence (for example snooker, pool, pong, air hockey . . . etc) . . . but if an object hits a surface and then slightly slows down (due to friction) the result will be that the angle of reflection will be more acute than it should be - this actually happens in real life too, but often in simulations we want the angle of reflection to perfectly match the angle of incidence . . . an issue you occasionally see on the forums is a bouncing object that was designed to continuously bounce around a scene, but after all while ends up bouncing back and forth in a straight line between two parallel surfaces (like a rectangular scene boundary) because on each bounce the angle of incidence becomes more and more acute until it is 0° (or close to 0°), you can solve this by turning friction to 0 for both actors.

    That was probably one of the most boring things I've posted here, and I've posted some boring stuff.

  • ArmellineArmelline Member, PRO Posts: 5,364

    @Socks said:
    That was probably one of the most boring things I've posted here, and I've posted some boring stuff.

    I strongly disagree! It's something that should be more common knowledge for sure!

  • PhilipCCPhilipCC Encounter Bay, South AustraliaMember Posts: 1,390

    @Armelline Another great tutorial. I was never clear on density. Now I am. Thanks. :)

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