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Thread: Particle FX Emitter help!

  1. #16
    Electron wrangler jwiede's Avatar
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    Aug 2007
    San Jose, CA
    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.
    Hmm, I stand corrected, must have been thinking of TP. I tested HVs with LW as far back as 9.3.1UB and none of them would produce "regular" particle output just using rate setting as per-sec (excluding stepped on/off envelopes or anything like that). Seems like it's always been that way since HVs were added.
    Last edited by jwiede; 07-14-2019 at 04:49 PM.
    John W.
    LW2015.3UB/2018.0.7 on MacPro(12C/24T/10.13.6),32GB RAM, NV 980ti

  2. #17
    Super Member
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    Dec 2009
    London, England, UK
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    Thanks for getting back to us and clearing that up.


  3. #18
    Right.... so Ive had a bit of a play around with all of the suggestions. You will have to forgive me, my report back is very much from my non-technical perspective:

    XswampyX - Thanks for the cool little scene file. I also learned something new from opening it and having a look at how you linked instanced objects to the particle emission. Very cool. It took me a while to replicate what you had done but eventually I got it to work. Im very keen to play around more with this setup to see if I can get the "repeat/loop" to work in between ON and OFF keyframes so that the gun can fire in regular bursts with breaks in-between.

    Shabazzy - Thanks for the suggestion to use velocity to generate the emission. I dont think this solution will be appropriate for what I am doing but its a great feature to know about so thanks!

    Prometheus - your suggestion of using the loop frame certainly seemed to work and seemed like the easiest solution. But I came unstuck with it when I started opening up the gap/size of that loop. When the loop spacing got larger, Lightwave's non regular emission started appearing again. Also this approach doesnt allow one to turn the firing on and off during the scene.

    tburbage - your expression solution islike a miracle to me! I copy pasted your expression and it just magically worked. I have no idea how this stuff works so I would never be able to replicate this without copy pasting, so thanks so much for passing on the expression. I'll definitely save it for future use. I think the only down side to the expression approach is the same problem with the loop frame. Its constant - so the whole scene would have the gun being "on" and firing non-stop. Unless there is a way to further control the expression?

    At the end of the day, I still wish there was a simpler solution to just keyframe the rate of emission you want and then choose "regular" or "random" as the generation pattern (if that makes sense).

    Thanks again for all your contributions and help with this.

    Cape Town, South Africa

  4. #19
    An update on XswampyX's technique of creating keys and using the repeat function. It seems I cant get this to "turn off" and then "turn on" again later in my scene. Its seems to produce an "always on" result like using an expression.

    What I am really looking for is a way to have a gun fire a burst, stop and then fire another burst. All of this at a timing or keyframes of my choosing. From what I can see, the only way I can make this happen is to keyframe every frame manually (what a pain).

    In the envelope graph Ive tried setting up a single shot or emission key and then copy pasting that to create a whole bunch of them, but the copy pasting of keyframes doesnt seem to work properly for me. Lightwave doesnt remember the stepped keyframe setting and pastes the new keyframes as TCB spline keys (even though the original keyframes I created were set to stepped).

    The paste function also doesnt paste at the point where the playback head/frame marker is but rather starts the paste on top of wherever the last keyframe is.

    Any ideas?

    I think at this point 3Dhotshot's suggestion of using a sound file to generate the particles is looking like the way to go for me...
    Last edited by scott.newman.ct; 07-15-2019 at 02:33 AM.

    Cape Town, South Africa

  5. #20
    Registered User
    Join Date
    Jan 2005
    Colorado Springs
    If you're going to end up adding sound, I'd create the soundtrack first and then use the Audio File envelope as suggested earlier, which I've used and works great.

    If you do want to "manually" trigger the machine gun bursts, I'd use an Expression and a TriggerNull to fire bursts. A sample scene is attached.

    In the Graph Editor for the Particle Emitter Birth Rate, you choose the Expressions tab, and enter an Expression of the form:


    The mod(Frame,6) gets the remainder of the Frame number divided by 6, which for a 30fps scene is 5 rounds per second or 300 rounds per minute. The question-mark syntax is a shorthand if-then-else, where the value before the colon is returned for TRUE and the value after the colon is returned for FALSE. The remainder for Frame / 6 (i.e. the mod() operator) will be 0 (i.e. FALSE) for frames 0, 6, 12, ..., so 1 will be returned, causes a birth-rate of 1 particle per frame. For other frames, the mod() operator will return non-zero (i.e. TRUE) and the birth rate will be 0.

    The [TriggerNull.Position.Y] portion retrieves the current Y position of the TriggerNull, which is normally 0.0 and you move it to 1.0 when you want the particles to start "firing", which is multiplied by the mod() operator to produce the particle bursts:

    Click image for larger version. 

Name:	Particles_GunFireEmitter_300rpm_WithTriggerNull_0063.jpg 
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ID:	145437 Click image for larger version. 

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    The sample scene has an Instancer on EmitterNull to instance a small copper-clad bullet object.

    Click image for larger version. 

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    Here's the setup:

    Click image for larger version. 

Name:	01_BirthRateExpression_300RoundPerMinute.jpg 
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ID:	145435 EmitterNull expression setup

    Click image for larger version. 

Name:	02_SteppedKeysOnTriggerNull_1point0_FiresBurst.jpg 
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ID:	145436 Stepped keys on TriggerNull Y Position to fire bursts of chosen lengths

    Attached Files Attached Files

  6. #21
    MonroePoteet, thank you so much for this. The sample scene you attached is perfect. While I dont quite fully understand the code/math behind the expression, I know enough to use it and edit it. This is such a valuable template scene! And thanks for being so thorough with explaining everything.

    I honestly dont know where I would be without these forums and the willingness of other Lightwave artists who share their time and knowledge.

    Thanks to everyone who made great suggestions here - its amazing how much one can learn just from one thread!

    Cape Town, South Africa

  7. #22
    Registered User
    Join Date
    Jan 2005
    Colorado Springs
    Glad it helped! Yes, the responsiveness in the forums is really valuable, and there's a huge amount of LW functionality which may not be obvious but is really powerful once someone introduces it (e.g. the Expressions). Reading through the *entire* LW manual and trying all the options isn't feasible, especially for a hobbyist such as myself, but sometimes it just takes a hint from a helpful forum member to get going in the right direction.

    Have fun!

  8. #23
    Registered User 3dhotshot's Avatar
    Join Date
    Mar 2009
    wow thats amazing !!!!!!!
    it really sucks ......

  9. #24
    Profesor Pixel Poo Mr Rid's Avatar
    Join Date
    Oct 2005
    Los Angeles
    Attached is a setup that uses a collision event to set the rate of fire. You might have to click Calculate for the emitter to follow the target. Tracer_fire_01.rar
    "O K, so what's the speed of dark?"

    Demo reel 2017

  10. #25

    Nice, Thank You to you both!

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