How to get the position of a vertex in a particles-shader?

Steven-1 · September 24, 2013, 7:48am

I’m writing a shader for a particle system (or rather trying to), that changes its look depending on its position in local space. (either the position of the particle, or of each individual vertices, doesn’t really matter much).
for meshes this is easy, you can directly access the local position in the vertex shader.
However, I tried this with a particle system, and it appears then that the vertex postion does not match the local postion, but rather some sort of weird screen space position.

So does anyone know how to get a particle’s (or its vertices) local or world space position in a shader?

Farfarer · September 24, 2013, 8:29am

It’s a bit tricky, this is the closest I’ve gotten;

gist.github.com

https://gist.github.com/Farfarer/158b23f694c2c995f93e

AutoLightParticle.cginc

// Helper macros specific to particles for lighting and shadows.
// Required.
// Keep this in the same directory as the other lit particle shader files.

#ifdef AUTOLIGHT_INCLUDED
	
	// ---- Screen space shadows
	#if defined (SHADOWS_SCREEN)
		#define TRANSFER_SHADOW_PARTICLE(a) a._ShadowCoord = ComputeScreenPos(o.pos);
	#endif

This file has been truncated. show original

Camera2World.js

#pragma strict

// Apply this to all of the cameras that will be rendering lit particles.

function OnPreCull () {
	Shader.SetGlobalMatrix ("_Camera2World", this.camera.cameraToWorldMatrix );
}

litParticleAdditive.shader

// Additive particle.
// Does not receive shadows.

Shader "Custom/Lit Particle Additive" {

	Properties {
		_Color ("Main Color", Color) = (1.0, 1.0, 1.0, 1.0)
		_MainTex ("Color (RGBA)", 2D) = "white" {}
	}

This file has been truncated. show original

There are more than three files. show original

Steven-1 · September 24, 2013, 8:01pm

looking at your code, it would seem all that needs to be done is multiply the vertex position with the Camera2World matrix.
but I tried that and it doesn’t seem to work,
am I missing something?

Edit:

no wait, my bad, that totally does work.

thanks Farfarer

Topic		Replies	Views
Particles object position Unity Engine Shaders , URP	1	2215	June 16, 2021
Local Particle Position Vertex Stream? Unity Engine Graphics	3	2118	November 22, 2022
Local space mesh with ParticleSystemRenderer Unity Engine Graphics	2	931	March 5, 2019
Particles shader struggling Unity Engine Shaders	5	866	November 20, 2017
getting the local vertex positions in vertex shader Questions & Answers legacy-topics	2	19328	February 21, 2015

How to get the position of a vertex in a particles-shader?

Related topics