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Thread: Particle FX Emitter help!

  1. #1

    Particle FX Emitter help!

    So this might seem like the most basic of basics.... but I cant get it to work properly.

    I am using a particle FX emitter to generate particles that need to behave like bullets coming from a gun. Firearms have set, regular rates of fire, so for example if an automatic rifle fires at 300 rounds per minute then thats 5 bullets leaving the barrel every second.

    So if I setup an emitter with the birth rate set to 5 and "generate by" set to "sec" and the velocity at around 800 m/s you would expect a nice regular stream of particles (at least I did).

    But it seems Lightwave doesnt generate the particles evenly. Is this normal or an error with my Lightwave?

    Im finding that sometimes two or three particles are generated together then there is a gap and a break in the generation and then a random particle will be generated. I suppose its still 5 per second, but its not nice and uniform and regular like I need.

    Does anybody know what the fix is here? I would really appreciate some help, thanks in advance.
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  2. #2
    Registered User squarewulf's Avatar
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    This might be a bug, I don't remember it behaving like this before 2018 / 2019. I can't get it to produce evenly spaced particles at all.

  3. #3
    Super Member XswampyX's Avatar
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    Use the graph editor and set the birthrate for the particles from 0 - 1 on every frame, 1 being the frame you want the particle generated.

    Click image for larger version. 

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    Have a look here...
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  4. #4
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    I don't think ParticleFX has ever created particles in a uniform manner (which is weird really) but the closet solution that I've managed to get is this:

    I've set my frame rate to 25 fps and in the FX Emitter settings, under the Generator tab I set the following:

    Birth Rate = 25
    Generate by = seconds
    Key Effect = Key

    Motion Tab
    Velocity X coordinate = -10m

    Then I set keys on the timeline for the emitter every 5 frames for the length of the shot.

    For some reason I get exactly 1 particle every 5 frames.

    Different framerates may need tweaking to the Birth Rate setting.

    I know it's not an ideal solution but I hope it helps.

  5. #5
    Electron wrangler jwiede's Avatar
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    Quote Originally Posted by Shabazzy View Post
    I don't think ParticleFX has ever created particles in a uniform manner (which is weird really)
    That definitely does not agree with my recollection, with birthrate set to per-sec versus per-frame and low enough I definitely recall evenly-spaced distributions would occur. I've still got installs all the way back to 9.3.3UB so testing it ought to be feasible tonight.
    John W.
    LW2015.3UB/2018.0.7 on MacPro(12C/24T/10.13.6),32GB RAM, NV 980ti

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    Quote Originally Posted by jwiede View Post
    That definitely does not agree with my recollection, with birthrate set to per-sec versus per-frame and low enough I definitely recall evenly-spaced distributions would occur. I've still got installs all the way back to 9.3.3UB so testing it ought to be feasible tonight.
    Yes, please do. I'd be interested in your findings.

  7. #7
    RETROGRADER prometheus's Avatar
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    use the etc tab and loop frame, try first with a value of one and see what happens, then
    a number close to what you want, not exactly accurate, but you can have your
    gun repeating shots this way.

    So if you specify a loop frame of 5, then every 5th frame it will fire of a particle, if set to one ..every frame it will fire a particle for a continuous stream of particles.

  8. #8
    Super Member tburbage's Avatar
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    Scott,

    I don't *think* PFX ever guaranteed a regular interval between emissions when you set Generate By to Seconds. Keying the Position.X of the emitter and using Key Effect = Key is a common approach as already mentioned. Unfortunately, it only recognizes actual keys (i.e. not Post Behavior = Repeat) so you have to key every event.

    Another approach is to set Generate By=Frame, an Envelope on Birth Rate, and attach an expression to <emitter_obj>.particlefx.birthrate, like:

    mod(Frame, 6) ? 0.0 : 1.0

    Here, I'm just hard-coding the emission frame interval of 6 (which would be right for your 5 rounds per sec, and an fps of 30)

    -Tom

    PS - FYI sometimes you have to hit Calculate to get stuff like this to evaluate correctly, for example, if you modify the expression.
    Last edited by tburbage; 07-13-2019 at 01:34 AM.

  9. #9
    Thanks for the replies everyone... I'll have a go at trying all of these suggestions. I gotta say, this problem seems kind of crazy to me. Surely one would expect the emission to be simple and regular by default, and then if you wanted something mroe complex or random there could just be a check box for "randomize emission".

    Anyone agree with that? Perhaps this could be a simple feature request to improve the Particle FX?
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  10. #10
    It is certainly worth a feature request. The particle system is overdue for a complete overhaul. This would be one of many things to address.
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  11. #11
    Registered User ianr's Avatar
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    Bump 1,000%

  12. #12
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by scott.newman.ct View Post
    Thanks for the replies everyone... I'll have a go at trying all of these suggestions. I gotta say, this problem seems kind of crazy to me. Surely one would expect the emission to be simple and regular by default, and then if you wanted something mroe complex or random there could just be a check box for "randomize emission".

    Anyone agree with that? Perhaps this could be a simple feature request to improve the Particle FX?
    As I mentioned, try loop frame, that will give you exact generation with even space between particle location and birth, to me that isnīt harder than that.

  13. #13
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    I'd agree that Prometheus' solution is the best choice here.

  14. #14
    Registered User 3dhotshot's Avatar
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    you can also try driving it with an accurate audio file if you have one...
    Last edited by 3dhotshot; 07-13-2019 at 05:04 PM.

  15. #15
    Registered User squarewulf's Avatar
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    Quote Originally Posted by 3dhotshot View Post


    you can also try driving it with an accurate audio file if you have one...
    clever

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