An Introduction To The Solid Particle System

The Solid Particle System, SPS, is a single updatable mesh rendered with one draw call. It is built by combining multiple copies of one or more model meshes which become the particles of the system. Once the SPS is built, it has the same properties as any other Babylon.js mesh - no more, no less. It can be scaled, rotated, translated, lit, textured, etc.

As a system of particles, it provides some methods to manage the particles. However, unlike the standard particle system, it provides no built-in behaviors. It has no emitters, no particle physics, no particle recycler nor particle movement. You have to implement your own behaviors.

Once you have a mesh model, or models, as a basis for the particles you follow these steps

• First, create your SPS with new SolidParticleSystem(name, scene);
• then, add a number of particles to the SPS from a mesh model with addShape(model, number);
• redo this as many times as needed with any model;
• When done, build the SPS mesh with buildMesh().

Your SPS is then ready to manage its particles by

• initiating their positions, colors etc. with initParticles();
• update the SPS and draw it with setParticles().

When you want to animate the particles by changing their properties over time you need to

• define their individual behavior withupdateParticle(particle);
• call setParticles() within the render loop.

Let's create an example

const SPS = new SolidParticleSystem("SPS", scene); // scene is required
const sphere = BABYLON.MeshBuilder.CreateSphere("s", {});
const poly = BABYLON.MeshBuilder.CreatePolyhedron("p", { type: 2 }, scene);
SPS.addShape(sphere, 20); // 20 spheres
SPS.addShape(poly, 120); // 120 polyhedrons
SPS.addShape(sphere, 80); // 80 other spheres
sphere.dispose(); //free memory
poly.dispose(); //free memory

const mesh = SPS.buildMesh(); // finally builds and displays the SPS mesh

At this stage, all the particles are displayed at the origin. So to separate them, we need to initiate some properties. Access to the individual particles is through the particles array, and the length of which is given by nbParticles.

We setup the function to initiate the particles

// initiate particles function
SPS.initParticles = () => {
    for (let p = 0; p < SPS.nbParticles; p++) {
        const particle = SPS.particles[p];
        //Place particles at random positions with a cube
      	particle.position.x = BABYLON.Scalar.RandomRange(-50, 50);
        particle.position.y = BABYLON.Scalar.RandomRange(-50, 50);
        particle.position.z = BABYLON.Scalar.RandomRange(-50, 50);
    }
};

then call it to apply the initiation, followed by setParticles to actually reconfigure the SPS mesh geometry and vertex data

//Update SPS mesh
SPS.initParticles();
SPS.setParticles();

A basic SPS: A Basic Solid Particle System Colored Green: Green Colored Solid Particle System With Texture: Solid Particle System With Textures

As well as position you can also set properties such as color or uv values. More on managing particles later in this section

Color individual particles: Individually Colored Solid Particles Texture individual particles: Individually Textured Solid Particles

While it can be useful to have an SPS that will not change, for example to represent an asteroid field or city buildings

there is much more you can do with an SPS.