Sources comprise of nodes that spawn particles into Flow. There is also the concept of Subemitters, basically sources that spawn particles based on a certain condition. For example, the Expire Submitter Source will spawn new particles when the current ones expire ( allowing for Fireworks type effects ).

Common Attributes

  • SpawNum - The number of particles to spawn at each frame

  • RegionIdx - The mesh region particles spawn from. Particles will be spawned at the same depth/layer ordering of the selected mesh region

  • SpriteImage - The single sprite image of the spawned particle

  • Use Sprite Animation - If checked, then a sequence of animated sprite images will be used over time for the spawned particle

  • SpriteAnimation - A list/sequence of Sprite Images to use when the Use Sprite Animation option is checked

  • SpriteAnimFramePause - How quickly the sequence of sprite images are switched/swapped out in a sequential looping fashion. The larger the pause, the slower the sprite animation

  • EmissionIdx - The emission idx number that this field affects. Particles emitted from a source have an emission idx number that you can supply. The field itself also has one. This means only particles with the same emission idx specified in this attribute will be affected by the field, the others will be ignored. This is useful if you want certain fields to affect particles from certain sources but not others.

  • Color[R/G/B/A] - The Red, Green, Blue and Alpha values ( from 0 to 1 ) of the particle

  • Size[X/Y/Z] - The size scale of the particle

  • LifetimeFade - How quickly the lifetime of the particle decreases

  • Lifetime - The total lifetime of the particle when spawned

  • TwistFactor - The amount of twist or rotation applied when affected by a field or solver

  • UseTrail - Whether the particle uses particle trails

  • TrailNum - The number of segments of the particle trail

  • Position[X/Y/Z] - The position where to spawn the particles from

  • Radius - The radius of the spawn location

  • AngleStart - The starting angle to spawn particles from

  • AngleEnd - The ending angle to spawn particles from

  • VelStart - The starting velocity to spawn particles from

  • VelEnd - The ending velocity to spawn particles from

  • AngleVelStart - The starting angular/rotational velocity to spawn particles from

  • AngleVelEnd - The ending angular/rotational velocity to spawn particles from

Radial Source


A Radial Source spawns particle from a location given a certain spawn radius. You can specify a range of values for the varying spawn direction and/or varying spawn velocities. The attributes of this node are described in the Common Attributes section.

Expire Submitter Source


The Expire Submitted Source spawns particles at locations where particles are expired ( removed from the simulation). For example, you might want to spawn particles where the original source particles have expired. ( Say you wanted to trigger mini explosions in your particle systems at the expiry locations to achieve a fireworks type effect ).


  • TriggerEmissionIdx - The emission idx the submitted is aware of. For example, if you wanted to spawn submitters for expired particles from a source which spawned particles with emissionIdx of 0, you should set this value to 0 so that it will only subemit with expired particles containing emissioIdx values of 0. Always make sure the EmissionIdx of ths subemitter is DIFFERENT from the TriggerEmissionIdx, otherwise your simulation will be overwhelmed with too many particles in a feedback loop!

  • MaxParticleLimit - The submitter will not spawn particles if the number of particles exceeds this limit