Fx Emitter 2D

Overview

Adds a particle source (emitter) to an FX state. It determines where particles appear, how many are emitted, which direction they travel, and their initial speed. For a flame, emit a few particles at a time upward from the bottom; for an explosion, emit them all at once in every direction from the center.

Usage tips

• The character of an effect is largely determined by choosing between rate (continuous emission for flames or smoke) and burst (all-at-once emission for explosions or impacts).
• Connect an image to mask to emit from a specified shape, such as igniting a character silhouette. The mask defines the emission area, not the appearance of each particle.
• Multiple emitters can be chained. Stack two emitters for layered FX such as a flame core plus surrounding sparks.

Related nodes

• fx_domain_2d — the upstream foundation
• fx_force — controls particles after emission
• fx_rasterize — controls particle appearance with a stamp
• path_mask — creates an emission-area mask

Key parameters

Read this first

• Fx Emitter 2D does not draw an image.
• It specifies where particles appear, how many are emitted, and which direction they travel.
• Fx Rasterize determines their actual appearance.
• Use mask to control emission positions with an image.

The role of mask

• mask does not define the appearance of a particle.
• It is an image that defines where particles may be emitted.
• White or opaque pixels permit emission.
• Transparent pixels prevent emission.
• mask_threshold sets the minimum alpha treated as active.
• Fully transparent pixels remain blocked even when mask_threshold = 0.

In short:

• To define emission positions with an image:
  • FxEmitter2D.mask
• To define the appearance of each particle with an image:
  • FxRasterize.stamp

When to use it

• To create a single source at the base of a flame
• To place multiple smoke sources
• To emit splashes or sparks primarily as a burst

The most basic setup

FxDomain2D -> FxEmitter2D -> FxRasterize

One emitter is enough to start. For a flame, these settings are easy to understand:

• shape = circle
• position = 16, 24
• radius = 2, 1
• rate = 2
• burst = 1
• direction = -90
• spread = 40
• speed = 0.5..1.5
• life = 3..6

Basic lane with a mask

PathMask / PixelCanvas / Image Load
  -> FxEmitter2D.mask

This is useful for effects such as:

• emitting smoke from the shape of text,
• emitting sparks from cracks in the ground, or
• emitting splashes only from white areas.

Example: emitter with a mask

{
  "shape": "circle",
  "position": [16, 24],
  "radius": [6, 3],
  "mask_threshold": 0.5,
  "rate": 3.0,
  "burst": 0
}

In this case, the node:

• first generates candidate positions within the circular area,
• emits when a candidate falls on a white part of mask, and
• does not emit when it falls on a transparent part.

Example

Example settings for a 32x32 flame:

{
  "name": "Flame Base",
  "shape": "circle",
  "position": [16, 24],
  "radius": [2, 1],
  "start_frame": 0,
  "end_frame": 7,
  "rate": 2.0,
  "burst": 1,
  "direction_deg": -90.0,
  "spread_deg": 40.0,
  "speed_min": 0.5,
  "speed_max": 1.5,
  "life_min": 3.0,
  "life_max": 6.0,
  "size_min": 1.0,
  "size_max": 2.0,
  "alpha_min": 0.5,
  "alpha_max": 1.0,
  "jitter": 0.4
}

Where it helps

• Flames: place one or two emitters near the bottom.
• Smoke: weaken direction and increase life.
• Splashes: increase burst and shorten life.

Changing density and size

• To increase density:
  • increase rate,
  • increase burst,
  • increase life_max so more particles remain on screen, or
  • reduce radius_x / radius_y or spread_deg to pack particles into the same area.
• To make particles larger:
  • increase size_min / size_max, and
  • apply an overall multiplier with FxRasterize.size_scale.

Examples:

• size_min = 1, size_max = 1
  • Emits only small particles.
• size_min = 2, size_max = 4
  • Varies each particle's size from 2 to 4.

Notes

• end_frame = -1 means “through the final frame.”
• Adding emitters increases the particle count.
• For P11, keep rate, life, and size low before the effect becomes too expensive.
• Even with mask connected, particles cannot be emitted from fully transparent areas.
• With shape = point, only one point is tested, so no particle is emitted when that point falls outside mask.
• If a speed, life, size, or alpha minimum exceeds its maximum, evaluation swaps the pair and shows a warning in the Inspector.
• If start_frame / end_frame falls outside the FX domain, or the end precedes the start, evaluation corrects the emission window and shows a warning.