Accessing Particle Amount or Spawnduration via script?

Hi El,

You can do this by transitioning the number of particles in and out before turning them off. We can do this by modifying the particleControlHelper to include a transition state. 

First we need to tell our particle system that we want to control the number of particles in the scene. Select your particle material and in its Inspector panel, tick the particle count box. 

Then let's modify our particleControlHelper script. At the top of the file, we can declare some variable that keeps track of our state. I also added a variable to define how fast we should change the spawnCount. Finally, we will record the spawnMaxParticles we set in the material settings so that we can transition to and from it. 

var transitionState = 0; // 0 none, 1 transition in, 2 particle showing, 3 transition out
var transitionSpeed = 10;
var spawnMaxParticles = meshVis.mainPass.spawnMaxParticles;

Then in the update function, after we set our externalTimeInput, we will modify the number of particles we are spawning based on the state above.

if (transitionState == 1) {
 meshVis.mainPass.spawnMaxParticles += transitionSpeed;

if (meshVis.mainPass.spawnMaxParticles >= spawnMaxParticles) {
 transitionState = 2
 }
 } else if (transitionState == 3) {
 meshVis.mainPass.spawnMaxParticles -= transitionSpeed;

if(meshVis.mainPass.spawnMaxParticles <= 0) {
 stopParticle();
 } 
 }

Notice that we call stopParticle here after our particle count is 0, rather than when particleStopEvent is called. 

Finally we'll modify how our particle system start and stop to account for the transition state. In the startParticle function, we will add

 meshVis.mainPass.spawnMaxParticles = 0;
 transitionState = 1;

to have our particle spawn count start from 0 then letting our update function know that we should increase it. 

Then we will add another function that tells our update loop to decrease the particle count when the particleStopEvent gets triggered, rather than stopping the particle instantly  

 function startTransitionOutParticle() {
 transitionState = 3;
 }

 var particleStopEvent = script.createEvent(script.particleStopper);
 particleStopEvent.bind(startTransitionOutParticle);

In our stopParticle function we will also set the transitionState to 0 to let our update loop know that we are not transitioning. 

transitionState = 0;

and now you should see your particles transitioning in and out!

Let me know if you have any other questions. Can't wait to see what you come up with. 

Cheers!

Jon

Our final script:

// ParticleControlHelper with Transition!
// Version: 0.0.1
// Event: Lens Initialized
// Description: Plays Particle on trigger

// @input string particleTrigger = TouchStartEvent { "widget": "combobox", "values": [ { "label": "Brows Lowered", "value": "BrowsLoweredEvent" }, { "label": "Brows Raised", "value": "BrowsRaisedEvent" }, { "label": "Brows Returned To Normal", "value": "BrowsReturnedToNormalEvent" }, { "label": "Face Found", "value": "FaceFoundEvent" }, { "label": "Face Lost", "value": "FaceLostEvent" }, { "label": "Kiss Finished", "value": "KissFinishedEvent" }, { "label": "Kiss Started", "value": "KissStartedEvent" }, { "label": "Mouth Closed", "value": "MouthClosedEvent" }, { "label": "Mouth Opened", "value": "MouthOpenedEvent" }, { "label": "Smile Finished", "value": "SmileFinishedEvent" }, { "label": "Smile Started", "value": "SmileStartedEvent" }, { "label": "Touch Start", "value": "TouchStartEvent" }, { "label": "Touch End", "value": "TouchEndEvent" }, { "label": "Tap", "value": "TapEvent" } ] }

//@ui {"widget":"separator"}
// @input bool stoppable = false 
// @input string particleStopper = TouchEndEvent { "widget": "combobox", "values": [ { "label": "Brows Lowered", "value": "BrowsLoweredEvent" }, { "label": "Brows Raised", "value": "BrowsRaisedEvent" }, { "label": "Brows Returned To Normal", "value": "BrowsReturnedToNormalEvent" }, { "label": "Face Found", "value": "FaceFoundEvent" }, { "label": "Face Lost", "value": "FaceLostEvent" }, { "label": "Kiss Finished", "value": "KissFinishedEvent" }, { "label": "Kiss Started", "value": "KissStartedEvent" }, { "label": "Mouth Closed", "value": "MouthClosedEvent" }, { "label": "Mouth Opened", "value": "MouthOpenedEvent" }, { "label": "Smile Finished", "value": "SmileFinishedEvent" }, { "label": "Smile Started", "value": "SmileStartedEvent" }, { "label": "Touch Start", "value": "TouchStartEvent" }, { "label": "Touch End", "value": "TouchEndEvent" }, { "label": "Tap", "value": "TapEvent" }], "showIf":"stoppable" }


// Get the Particle's Mesh Visual
var meshVis = script.getSceneObject().getFirstComponent("Component.MeshVisual");
// Variable to store what time particle started
var startTime;

var transitionState = 0; // 0 none, 1 transition in, 2 particle showing, 3 transition out
var transitionSpeed = 10;
var spawnMaxParticles = meshVis.mainPass.spawnMaxParticles;

// Update the particle time every frame when needed
function update()
{
 if (startTime) 
 {
 // Calculate how many seconds have elapsed since we've triggered partcles
 var particleTime = getTime() - startTime;

// Pass it in to our Particle Material
 meshVis.mainPass.externalTimeInput = particleTime;

if (transitionState == 1) {
 meshVis.mainPass.spawnMaxParticles += transitionSpeed;

if (meshVis.mainPass.spawnMaxParticles >= spawnMaxParticles) {
 transitionState = 2
 }
 } else if (transitionState == 3) {
 meshVis.mainPass.spawnMaxParticles -= transitionSpeed;

if(meshVis.mainPass.spawnMaxParticles <= 0) {
 stopParticle();
 } 
 }
 }

}
var updateEvent = script.createEvent("UpdateEvent");
updateEvent.bind(update);


// On an event, store the time when particle is triggered
function startParticle()
{
 startTime = getTime();
 meshVis.mainPass.spawnMaxParticles = 0;
 transitionState = 1;
}
var particleTriggerEvent = script.createEvent(script.particleTrigger);
particleTriggerEvent.bind(startParticle);


if (script.stoppable) {
 // On an event, store the time when particle is triggered
 function stopParticle()
 {
 transitionState = 0;
 startTime = 0;
 meshVis.mainPass.externalTimeInput = 0; 
 }

function startTransitionOutParticle() {
 transitionState = 3;
 }

var particleStopEvent = script.createEvent(script.particleStopper);
 particleStopEvent.bind(startTransitionOutParticle); 
}