Particle question

Hi Karl,

Our particle system is shader based, which makes it efficient for simulating many particles, but focused in a local space.

However, you can simulate a world particle system by spawning multiple local particle systems in world space.

Let's start by creating a script. In the Objects panel, press Add New > Empty Object. Then select that object and in its Inspector panel, press Add Component > Script. This object and this script will be our World Particle Controller.

Select this script in the Resources panel to edit it. First let’s set up some input to help us. We need to know how long a particle system should last, how many particle system should exist in total, and how often we should create one. Then we need to have a reference to the particle system we’re going to copy. Make sure to connect your particle to this input.

//@input float animationLength = 5
//@input int maxParticleSystems = 50
//@input float spawnInterval = 0.01
//@input SceneObject particle

Each copy of the particle system needs to have their own material so they can each have a different state. To do so, we will store a copy of the particle materials.

// Store copy of original particle system
var copyableMeshVisual = script.particle.getFirstComponent("Component.MeshVisual");
var copyableMaterial = copyableMeshVisual.mainMaterial.clone();

Then we’ll create some store to references all particle systems.

// Initialize variables to store the particle systems in
var instances = []; // Each particle system
var startTimes = []; // When that particle system started
var matPasses = []; // The particle system's material

Finally, we’ll need to know the overall state of our world particle system.

// Keep track of our particle systems
var lastSpawnTime = 0; // When we last started a particle system
var nextSpawnIdx = 0; // Index of the particle system we should modify next

Next we will create all our different particle systems by dynamically creating an object and adding a copy of our particle’s mesh visual and materials.

// Generate all our particle systems
for (var i = 0; i < script.maxParticleSystems; i++) {
 var newObject = global.scene.createSceneObject("Particle_Trails");
 newObject.enabled = false;

var mv = newObject.copyComponent(copyableMeshVisual);
 mv.clearMaterials();
 mv.addMaterial(copyableMaterial.clone());

var material = mv.getMaterial(0).getPass(0);
 material.externalSeed = Math.random();

instances.push(newObject);
 startTimes.push(0.0);
 matPasses.push(material);
}

Next let’s set up a loop to manage the created particle system over time.

function onUpdate(eventData) {
 updateWorldParticles();
}
var event = script.createEvent("UpdateEvent");
event.bind(onUpdate);

Finally, we’ll update our particle systems! For all particle systems, we need to update the time to progress the system forward. Additionally, every time our current time minus the last spawn time, is greater than our spawn interval, we position a particle system where we are and restart it.

function updateWorldParticles(){
 var currentTime = getTime();
 var t = currentTime - lastSpawnTime;

// Update all particle system's time
 for (var i = 0; i < script.maxParticleSystems; ++i) {
 var timeOffset = startTimes[i];
 var obj = instances[i];
 var pass = matPasses[i];
 var shaderTime = currentTime - timeOffset;

if (shaderTime > script.animationLength)
 obj.enabled = false;
 else
 pass.externalTime = new vec4(0.0,shaderTime,1.0,1.0);
 }

// Restart particle system's position at current pos as needed
 if (t > script.spawnInterval) {
 var currentPos = script.particle.getTransform().getWorldPosition();
 var index = nextSpawnIdx % script.maxParticleSystems;
 var instance = instances[index];

lastSpawnTime = currentTime;
 startTimes[index] = currentTime;

instance.enabled = true;
 instance.getTransform().setWorldPosition(new vec3(currentPos.x,currentPos.y,currentPos.z));
 
 nextSpawnIdx++;
 }
}

Now, when you move around the particle system, you should see a trail of particles behind!

Here’s a sample project to help you get started.

Don’t forget to share your final result!

Cheers,
Jon