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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.

    dom


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    Archive Notice: This thread is old and no longer active.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 Please keep that in mind as you view this thread, as many of the topics and opinions may be outdated.
     
    abnormal

    January 23, 2002, 02:56 PM

    nice effects, the water looks "interessting" (a bit to transparent and tiled).

     
    Peter Mackay

    January 23, 2002, 02:59 PM

    Which is on his todo list!

     
    Sabman

    January 23, 2002, 03:01 PM

    severly interesting, I can't wait to see the finish...

    -Sabman

     
    Flying Wombat

    January 23, 2002, 03:06 PM

    That is an awesome pic! You could implement a skywriter simulation, haven't heard of many of those ;) Really nice.

     
    Alex May

    January 23, 2002, 03:36 PM

    Nice, but I've always thought that contrails could be done in a less processor-intensive way, yet look better. Your shots look a lot like a particle system to me, rather than a "smooth flame effect". I'm sure it looks better moving :)

    Try using fewer particles, making them bigger and using several animated textures for the flames (to avoid repetition effects). Take a look at the Return To Castle Wolfenstein flamethrowers - they look great (lost of particles though...).

    Another plan might be to use some kind of poly system like the rocket trails in Half-Life (except better of course ;).

    One thing I like about contrails/smoke trails is when they last for ages. If you used fewer particles for the trail, you could make it much longer (and have the fire particles turn in to smoke/condensation particles :)

    Keep it up, you've got much further than me :)

     
    maddoc

    January 23, 2002, 03:44 PM

    I'm sure you know the basics of HTML ;-)

     
    Sabman

    January 23, 2002, 03:46 PM

    Pirating motsly...

     
    Tim Wojtaszek

    January 23, 2002, 04:04 PM

    if your trying for a fire effect..the goal should be emulate what hugo elias has done.

    freespace.virgin.net/hugo.elias

     
    dan ogles

    January 23, 2002, 05:03 PM

    Is the particle system framerate-independent? If so, how do you interpolate the position of the emitter between two samples?

     
    dom

    January 23, 2002, 05:16 PM

    Dan,

    Yes, it's fps-independent. I'm not too sure what you mean here; what do you mean by 'samples'? Frames?

    If so, there's no interpolation _between_ frames, just framerate modified movement _each_ frame, so (vPos += vVel * (60.0f/fFPS)). I always use (60/fps) as the modifier to achieve fps-independance, coz it's 1 at my target framerate.

     
    dom

    January 23, 2002, 05:17 PM

    Yeah I know the water sucks big time... :o

     
    dom

    January 23, 2002, 05:19 PM

    Thanks!

    A skywriting simulator?! Now that's pretty crazy... hm... nah, I've got my projectiles working now, so I guess it'll be a plain old shoot em up. I was toying with the idea of a 3D Worms-type game for a while though, that would still be so cool...

     
    Obble

    January 23, 2002, 05:37 PM

    Just an idea to make it more reallisic.

    if the rocket is being propell thru the air, then
    nutons nth law = every force has a = but opposite reforce.
    somthing like that.

    that means that the trail of frames should be shot out of the rocket
    instead of just being place there in the air.


    like with a real rocket ie NASA, the flames go down and spread out
    not a move rocket place flames in air where rocket use to be.


    is that the .x model from the DX-SDK?


     
    SirKnight

    January 23, 2002, 05:56 PM

    You're refering to Newton's 3rd law of motion which states, 'for every action there is an equal and opposite reaction.' Meaning that the size of the force on the first object equals the size of the force on the second object but in the opposite direction.

     
    krogoth

    January 23, 2002, 06:03 PM

    How are those particles drawn? If you're using OpenGL, you could probably use GL_POINTS after making them round and the right color. They wouldn't look perfect, but with lots of small ones it shouldn't look to bad (not that I've tried it yet). It'd probably be a nice framerate boost over sprites...

     
    ch!ckuaua

    January 23, 2002, 06:05 PM

    The particles look cool, but I can tell from my own experience that a never-ending todo list causes that a project making process never ends ;)))

    Check this device(s) with whose help you could become immortal!!!

     
    Pixelish

    January 23, 2002, 06:19 PM

    Nice pic! And I agree somer weapons effects would look cool with that.

    In somewhat relation to this IOTD:
    Has anybody seen the videos for EVE - The second genesis? Any idea how they do their trails? It looks stunningly beautiful.
    If somebody knows how to do those, please explain or refer. Thx.

    Pixelish

     
    Mastaba

    January 23, 2002, 06:28 PM

    Actually, if you go into the mechanics of rocketry, you'll see that in the early stage of the rocket the exhaust is indeed moving down (assuming the rocket is going up). But later on a point is reached where the exhaust moves up. The exact point this occurs is dependent upon velocity of the exhaust relative to the rocket.

     
    kewldude

    January 23, 2002, 06:36 PM

    Point sprites will have sharp edges to start with, and they will not be faster.

     
    Morgan

    January 23, 2002, 10:59 PM

    Rockets don't go up because they are pushing exhaust fumes out the back-- you'd need an awful lot of mass to make that work since the center of mass would not move anyway. Rockets move because they are sitting on top of an explosion, which expands and pushes them as it releases energy. Since the source of that explosion is being accelerated along with the rocket, it is possible for the waste gasses to go up, down, or sit still depending on how fast that rocket is going and how fast the explosion is expanding.

    -m

     
    LeP

    January 24, 2002, 03:29 AM

    Not that im a rocket scientist or anything but...

    "Rockets don't go up because they are pushing exhaust fumes out the back"...umm actually they do...

    "you'd need an awful lot of mass to make that work"...its the combination of mass and velocity that make the thing work. The rocket shoots the gas out at extremely high velocities. But the thing starts with like over a million pounds of fuel.

    "Rockets move because they are sitting on top of an explosion, which expands and pushes them as it releases energy"...The explosion accelerates the gas, which makes the rocket move. the explosion doesn't blow the rocket upward. When you're in the middle of the air, the explosion has nothing to push on.

    Anyway, i might be a little off with some of this stuff, but you were so off i had to say something...for those interested:

    http://www.howstuffworks.com/rocket.htm

     
    Espyria

    January 24, 2002, 03:34 AM

    Your comment seems strange I think. I mean, what happens if you put the exhaust pipe on top of the rocket instead? Will the rocket still find it's way to the sky? I think not.

     
    Luke Philpot

    January 24, 2002, 04:32 AM

    That truely looks sweet.

     
    z80

    January 24, 2002, 04:37 AM

    Its Newtons third law: "For every action, there is an equal and opposite reaction."

    Mass is getting thrown off the rocket, and the rocket is moving the opposite direction. In space that is (so far) the best way to move, unless you use gravity or a solar particle sail to get where you want.

     
    MadCow

    January 24, 2002, 04:43 AM

    Here is my suggestion for making the particle system more realistic looking.
    How about streching the particles along their path of movement? That would remove the doddedness of the contrail. Another suggestion would be to have the colour and transparrency vary along the lifetime of the particle. New particles would be blue, turning yellow, and finally gray or something like that.

    Have you ever seen a plane having a contrail like the one simulated on this IOTD? I would hit the eject button if I were the pilot. :)

     
    d9930380

    January 24, 2002, 06:57 AM

    It's looking good so far however, I agree that using ~2000 point sprites for any "effect" is alot.

    You could use larger more detailed particles when they are first created and then as they spread apart and fade away, make them smaller.

     
    d9930380

    January 24, 2002, 07:06 AM

    You could also bend Space-Time to bring the destination point to you instead of going to it. :-)

     
    _Tom

    January 24, 2002, 07:43 AM

    expanding on what Mastaba said
    particles should be give the velocity of the rocket and then the a velocity should be added to this of the speed of the ejection of the particles in relation to the rocket itself.

    particle velocity = (rocket velocity) + (ejection speed)*(-(~rocket velocity))

    i am using ~ to denote a normailzed vector.

    of couse you wil probably want to add a small random vector to facilitate spreading of the particles

     
    drZool

    January 24, 2002, 10:32 AM

    Hi!
    You're on your way with this. I haven't read all comment, but have you seen MaxPayne's FXeditor? You should! You might get some idas from there.

     
    Buster

    January 24, 2002, 11:17 AM

    Mmmm, powerups. It's all about the powerups baby!

     
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