Mesh Particle Emitter
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Mesh Particle Emitter

The Mesh Particle Emitter emits particles around a mesh. Particles are spawned from the surface of the mesh, which can be necessary when you want to make your particles interact in a complex way with objects.


The Mesh Particle Emitter Inspector

Properties

EmitIf enabled, the emitter will emit particles.
Min SizeThe minimum size each particle can be at the time when it is spawned.
Max SizeThe maximum size each particle can be at the time when it is spawned.
Min EnergyThe minimum lifetime of each particle, measured in seconds.
Max EnergyThe maximum lifetime of each particle, measured in seconds.
Min EmissionThe minimum number of particles that will be spawned every second.
Max EmissionThe maximum number of particles that will be spawned every second.
World VelocityThe starting speed of particles in world space, along X, Y, and Z.
Local VelocityThe starting speed of particles along X, Y, and Z, measured in the object's orientation.
Rnd VelocityA random speed along X, Y, and Z that is added to the velocity.
Emitter Velocity ScaleThe amount of the emitter's speed that the particles inherit.
Tangent VelocityThe starting speed of particles along X, Y, and Z, across the Emitter's surface.
Simulate In World SpaceIf enabled, the particles don't move when the emitter moves. If false, when you move the emitter, the particles follow it around.
One ShotIf enabled, the particle numbers specified by min & max emission is spawned all at once. If disabled, the particles are generated in a long stream.
Interpolate TrianglesIf enabled, particles are spawned all over the mesh's surface. If disabled, particles are only spawned from the mesh's vertrices.
SystematicIf enabled, particles are spawned in the order of the vertices defined in the mesh. Although you seldom have direct control over vertex order in meshes, most 3D modelling applications have a very systematic setup when using primitives. It is important that the mesh contains no faces in order for this to work.
Min Normal VelocityMinimum amount that particles are thrown away from the mesh.
Max Normal VelocityMaximum amount that particles are thrown away from the mesh.

Details

Mesh Particle Emitters (MPEs) are used when you want more precise control over the spawn position & directions than the simpler Ellipsoid Particle Emitter gives you. They can be used for making advanced effects.

MPEs work by emitting particles at the vertices of the attached mesh. Therefore, the areas of your mesh that are more dense with polygons will be more dense with particle emission.

Particle Emitters work in conjunction with Particle Animators and Particle Renderers to create, manipulate, and display Particle Systems. All three Components must be present on an object before the particles will behave correctly. When particles are being emitted, all different velocities are added together to create the final velocity.

Spawning Properties

Spawning properties like Size, Energy, Emission, and Velocity will give your particle system distinct personality when trying to achieve different effects. Having a small Size could simulate fireflies or stars in the sky. A large Size could simulate dust clouds in a musky old building.

Energy and Emission will control how long your particles remain onscreen and how many particles can appear at any one time. For example, a rocket might have high Emission to simulate density of smoke, and high Energy to simulate the slow dispersion of smoke into the air.

Velocity will control how your particles move. You might want to change your Velocity in scripting to achieve interesting effects, or if you want to simulate a constant effect like wind, set your X and Z Velocity to make your particles blow away.

Simulate in World Space

If this is disabled, the position of each individual particle will always translate relative to the Position of the emitter. When the emitter moves, the particles will move along with it. If you have Simulate in World Space enabled, particles will not be affected by the translation of the emitter. For example, if you have a fireball that is spurting flames that rise, the flames will be spawned and float up in space as the fireball gets further away. If Simulate in World Space is disabled, those same flames will move across the screen along with the fireball.

Emitter Velocity Scale

This property will only apply if Simulate in World Space is enabled.

If this property is set to 1, the particles will inherit the exact translation of the emitter at the time they are spawned. If it is set to 2, the particles will inherit double the emitter's translation when they are spawned. 3 is triple the translation, etc.

One Shot

One Shot emitters will create all particles within the Emission property all at once, and cease to emit particles over time. Here are some examples of different particle system uses with One Shot Enabled or Disabled:

Enabled:

Disabled:

Interpolate Triangles

Enabling your emitter to Interpolate Triangles will allow particles to be spawned between the mesh's vertices. This option is off by default, so particles will only be spawned at the vertices.


A sphere with Interpolate Triangles off (the default)

Enabling this option will spawn particles on and in-between vertices, essentially all over the mesh's surface (seen below).


A sphere with Interpolate Triangles on

It bears repeating that even with Interpolate Triangles enabled, particles will still be denser in areas of your mesh that are more dense with polygons.

Systematic

Enabling Systematic will cause your particles to be spawned in your mesh's vertex order. The vertex order is set by your 3D modeling application.


An MPE attached to a sphere with Systematic enabled

Normal Velocity

Normal Velocity controls the speed at which particles are emitted along the normal from where they are spawned.

For example, create a Mesh Particle System, use a cube mesh as the emitter, enable Interpolate Triangles, and set Normal Velocity Min and Max to 1. You will now see the particles emit from the faces of the cube in a straight line.

See Also

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