# Ignition Rendering

## API Reference

5.1.0
Particles

This example shows how to include a particle emitter in the scene.

## Compile and run the example

Clone the source code, create a build directory and use cmake and make to compile the code:

git clone https://github.com/ignitionrobotics/ign-rendering
cd ign-rendering/examples/particles_demo
mkdir build
cd build
cmake ..
make

Execute the example:

./particles_demo

You'll see:

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TAB - Switch render engines
ESC - Exit
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## Code

A particle emitter generates a stream of particles. We can create a particle emitter in the same way we create other objects in the scene. We just need to use the scene to create the emitter using the method CreateParticleEmitter. It's possible to configure a few attributes of the emitter and its particles:

• Type: EM_POINT emitters emit particles from a single point. EM_BOX, EM_CYLINDER and EM_ELLIPSOID emitters emit randomly from a box, cylinder or ellipsoid respectively.
• Emitter size: Adjust the dimensions of the volume from which the particles are emitted.
• Rate: Set the amount of particles per second emitted.
• Duration: This parameter can be used to automatically disable the emitter after some time.
• Emitting: Enable/Disable the emission of particles.
• Particle size: Adjust the particle dimensions.
• Lifetime: Set the amount of seconds each particles "lives" before being destroyed.
• Material: Set the material which all particles in the emitter will use.
• Velocity: Set a velocity range and each particle is emitted with a random velocity within this range.
• Color range: Set the color for all particles emitted. You have two options to set the color.
• Using two color values: The actual color is interpolated between these two colors along the lifetime of the particle.
• Using an image: The colors are taken from a specified image file. The range of color values begins from the left side of the image and move to the right over the lifetime of the particle, therefore only the horizontal dimension of the image is used.
• Scale rate: Adjust the amount by which to scale the particles in both X and Y direction per second.

Here's the snippet of code from examples/particles_demo/Main.cc that includes a particle emitter to render particles to look like smoke:

ParticleEmitterPtr emitter = _scene->CreateParticleEmitter();
emitter->SetType(EM_POINT);
emitter->SetLocalPose({2, 1.10, 1.25, 1.5708, 0, 2.3});
emitter->SetRate(10);
emitter->SetParticleSize({1, 1, 1});