CPUParticles2D dynamic emission rate?

Shale · April 10, 2025, 3:13pm

Godot Version

v4.4

Question

What I want is simple emission by distance, but this is not currently supported and there is an issue open here:

github.com/godotengine/godot-proposals

Particle system: Add emission by distance travelled between emits (instead of time)

opened 01:03AM - 02 May 20 UTC

ghsoares

topic:rendering

**Describe the project you are working on:** A simple top-down shooter where I …have high-speed rocket launcher adn the rocket leaves smoke behind. **Describe the problem or limitation you are having in your project:** The particles system (2D and 3D) are leaving a "gap" between particles when local coords speed is high or the system is set to global coords and the parent speed is high. In the Unity engine, we have a option to emit particles by distance that creates new particles in between gaps **Describe the feature / enhancement and how it helps to overcome the problem or limitation:** To overcome the problem, it would be great if there was an option to emit by distance, like in Unity engine. **Describe how your proposal will work, with code, pseudocode, mockups, and/or diagrams:** In my mind, it can have two new properties: "rate by distance" and "minimal distance delta", then if the distance from previous global position and current global position is higher than minimal distance delta, then creates new particles between this gap. In a custom particles shader, I can't just create new particles because there's pre-defined amount of particles that restarts to "create new ones". So in pseudocode we could have (thinking in a particles shader): ```glsl uniform float min_distance_delta; uniform int interpolation_emission_step; uniform int rate_by_distance; void vertex() { vec3 previous_position; //some kind of previous particle system global position read vec3 current_position; //some kind of current particle system global position read float distance = distance(current_position, previous_position); if (distance > min_distance_delta) { //calculates every position using interpolation_emission_step //and creates new particles in each position } } ``` I don't know if with current particles system shader API, it's possible to create options to read previous and current position and create new particles besides the already alocated ones. **If this enhancement will not be used often, can it be worked around with a few lines of script?:** I think that it can't be made with gdscript or C# for performance reasons, as the only way is to instantiate new particles systems **Is there a reason why this should be core and not an add-on in the asset library?:** Because there are many projects that have high-speed gameplay and uses particles with global coords (a racing game where has tires smokes in drifting, for example), so it would be nice to be a main feature

So I tried implementing it manually by changing the amount based on distance/velocity but this resets the particle emitter as mentioned here:

github.com/godotengine/godot-proposals

Dynamically adjust the amount of particles emitted without clearing all the particles

opened 06:07AM - 15 Dec 22 UTC

chrisb123

topic:rendering topic:particles

### Describe the project you are working on Change the amount of particles to… visually indicate a change that does involve clearing existing particles ### Describe the problem or limitation you are having in your project Tho only way to change the amount of particles is to change the total amount which clears all particles ### Describe the feature / enhancement and how it helps to overcome the problem or limitation Don't emit particles based on a user provided ratio. Particles live out their life as normal, when they are due for restart they are tested based the ratio they are not submitted ### Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams User enters a ratio number, eg. 0.01 means 1% of amount and 1.00 would be every particle. The default is 1 to avoid breaking existing projects ### If this enhancement will not be used often, can it be worked around with a few lines of script? It's particles best to fix this in engine. I have no idea of any other suitable solution ### Is there a reason why this should be core and not an add-on in the asset library? I have no idea how to efficiently solve this except for core. I have a working example in engine for cpu particles 2D & 3D that has this feature https://discord.com/channels/212250894228652034/218361207990648832/1052569941888475136 ![image](https://user-images.githubusercontent.com/1736172/208052274-9a0dd36f-508f-4d59-8562-164e90540a4f.png)

So in the current version of Godot is there any way to dynamically emit particles without just instantiating an entire new particle system every time?

Shale · April 11, 2025, 10:40am

It seems like for now the only performance-minded solution is to convert to GPUParticles2D and use the amount_ratio field.

I have created a pull request to also implement this for CPUParticles2D.

github.com/godotengine/godot

Add `amount_ratio` to cpu particles to dynamically change amount emitted

godotengine:master ← Ducklett:particles-dynamic-amount

opened 06:07PM - 10 Apr 25 UTC

Ducklett

+98 -2

Revival of #79527 This PR implements the `amount_ratio` field for `CPUPartic…les2D` and `CPUParticles3D`. This already landed for `GPUParticles2D` and `GPUParticles3D` back in Godot v4.2 but the original PR for CPU particles never made it in. **Changes from the original PR** - changing `amount_ratio` will no longer change the `emitting` flag - updated docs for `amount` and `amount_ratio` to match those for `GPUParticles2D` and `GPUParticles3D` Fixes godotengine/godot-proposals#5939