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Submitted by Dominic Morris, posted on January 23, 2002

Image Description, by Dominic Morris

I’m really pleased; I’ve finally got my ‘contrail’ particle system working perfectly! =)

This system was giving me lots of grief; basically, it’s a particle-system model of a rocket trail, or contrail. I was having difficulty making the particle system move with the ship and render convincingly at all times - stuff life turning 360 degrees on the spot used to cause the system to show itself for what it really is, i.e. a bunch of dots, instead of a smooth flame effect… anyhow, the images show a ship with two ‘contrail’ emitters; they spin round with the ship – you can draw double-helix trails in the sky with them! =) I’m going to do something similar for the weapons system (this ship would be very cool with the weapon spinning round – with four weapon emitters very far apart).

There’s probably ~2000 pointspirtes in these piccies and that hurts the framerate pretty bad of course, but what better way to use my new GF3?! Next up on my never ending list of things to do is:
  • Enemy ships
  • Powerups
  • Mines
  • BIG weapons
  • Prettier water
  • Reflections + Shadows
  • … it never ends.


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    Archive Notice: This thread is old and no longer active. It is here for reference purposes. This thread was created on an older version of the flipcode forums, before the site closed in 2005. Please keep that in mind as you view this thread, as many of the topics and opinions may be outdated.

    January 24, 2002, 11:26 AM

    Quite possible, but to do that you'd have to survive enough G's that's being made to bend that time into, shall we say, perspective? Besides, wouldn't the condencing of time cause a strain upon the current timeline, but the fact that, not only will the same occurances be happening at the same time, but you'll be able to talk to yourself?



    January 24, 2002, 11:30 AM

    That colour is a nice warning sign, helps to avoid your posts...


    January 24, 2002, 11:33 AM

    Well, I was told to take it off, so we'll have to come up with another warning sign, neh?



    January 24, 2002, 11:34 AM

    I like it! Don't worry about the particle system, mate, it looks okay when it dissolves into dots at the tail end. What you could do is perhaps have an alpha gradient where the tail end just fades out, it would make even cooler effects in my opinion.

    BIGGER weapons
    PRETTIER water
    Reflections + Shadows
    By the way, here are some other things you should work on:
    ENEMY ships




    January 24, 2002, 11:38 AM

    I'm assuming that the plane is not driven by rocket action but rather by jets under the wings or some such, and the exhaust doesn't really propel it (i.e. it doesn't push against the exhaust) as much as the air it flies in. As far as the rocket flames going down and spreading that's mostly because of the air retarding their action and dissipating them, and on the ground it's much more since the ground stops them and they spread out. Yeah, the trails from the airplane shoulddefinitely become less dense and more blurry and spread out. As you can see with real airplanes flying overhead, that leave trails.



    January 24, 2002, 01:49 PM

    Hi all,

    Thanks for the nice comments. Lots of you have mentioned colour fades, and I'm sure looking into doing this.

    Proper contrails are _very_ difficult if not impossible to do with a particle system; they hang around for ages, and span miles and miles. To do that with particles would require tens if not hundreds of thousands, because the particles have to _touch_ each other to form a continuous contrail. The only way would be with quads, I think.

    Also, per-vertex pointsprite sizes aren't supported on my GF3 (to my surprise). That kind of limits some of the suggestions that have been made. The whole system has to rendered in one batch, which means with one pointsize. The colours of course can be changed.

    MadCow: yeah, I'd eject aswell! ;)

    Buster: u r damn right, POWERUPS are where it's at, baby!

    I've put in some laser and bullet effects, and I've now added 50 enemy ships (single vertex-buffer); 'contrails' are now frustrum-culled, i think I'll also need to cull the _animation_ of these 50 particle systems (50x2000 velocity updates per frame, urgh)... =)


    Scott Velasquez

    January 24, 2002, 02:29 PM

    I love IOTD, but it's ignorant people like abnormal who find nit picky shit to complain about. He's demonstrating his particle engine NOT his water.


    January 24, 2002, 03:55 PM

    Ok, we've gotten into twilight zone scifi einstein roddenberry territory :)

    Rocket moves because it releases exhaust. The exhaust:
    1) pushes against a ground or atmosphere due to its initial velocity
    2) increases its effect by expanding and pushing the rocket a bit more
    3) the center of mas remains the same but as the exhaust is left behind the rocket goes forward

    This is only needed for acceleration in a certain direction while the rocket is not influenced majorly by gravity, and inertia can take over otherwise. Taking off from the moon the rocket only pushes against something for the first few seconds as it takes off. After that it's the space principle.



    January 24, 2002, 04:31 PM

    hey, wait a minute...

    i'm already able to talk to myself..

    maybe i shouldn't have messed with the time-space continuum...

    Q? help..


    January 24, 2002, 09:20 PM

    If you want good particles I think quads are the way to go, I think a good contrail effect would be it starts out transparent then quickly to blue then quickly to yellow then orange-ish then grey... the particles are getting bigger this whole time and then when they're grey they fade away over a couple seconds.

    Allan Parker

    January 25, 2002, 10:57 AM


    Wim Libaers

    January 25, 2002, 01:34 PM

    Another simple way to think about it. Take a cube with the bottom side removed, and make the pressure inside higher than outside. What happens? No sideways motion: the force on front, back, left and right sides compensate each other. The cube will move upwards, as the force on the upper side is greater on the bottom side. At the same time, due to the high pressure some of the gas flows out of the cube at the bottom.

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