Additional GPU Data

Since 2.0.0

Photon2 lets you send extra per-particle vertex attributes to the GPU — such as age, T, or velocity.

Note:
- This feature requires GPU Instance mode.
- Currently supported only for Particle Emitters (support for other FX objects will come later).
- Modifying vanilla vertex formats is difficult and sending large amounts of per-vertex data is inefficient, hence this separate system.

---

Particle Emitter

In the Particle Emitter Inspector, enable Additional GPU Data and select the data fields you need.

Supported Data Types

Data	Type	Description
T	float	Normalized lifetime: age / lifetime
Age	float	Particle age
LifeTime	float	Particle lifetime
Position (local)	vec3	Particle local position
Velocity	vec3	Particle velocity
isCollided	float	1 = collided, 0 = not yet
Emitter T	float	Emitter normalized lifetime
Emitter Age	float	Emitter age
Emitter Position	vec3	Emitter world position
Emitter Velocity	vec3	Emitter velocity

---

🛠 Shader Setup

Extra attributes are appended sequentially after the default vertex layout in the vertex shader (vsh).

⚠ Warning:
- Always place new attribute declarations after #moj_import <photon:particle.glsl>.
- GPU & driver behavior may vary; sequential layouts may not always be reliable — use layout(location = x) to explicitly bind attributes when needed.

Example: If you enable T and Velocity, add them to your shader:

#version 330 core

#moj_import <photon:particle.glsl>

in float T;
in vec3 velocity;

/*
layout(location = 9) in float T;       // Explicit location binding
layout(location = 10) in vec3 velocity;
*/

void main() {
    // Use the extra attributes here...
}

---

✅ Pro tip:
Keep your layout indices organized — mismatches between the emitter’s attribute order and shader declarations can cause rendering glitches or incorrect values.