# Increment Strip Index On Start

Menu Path: **Spawn > Custom > Increment Strip Index On Start**

The **Increment Strip Index On Start** Block helps to manage the initialization of Particle Strips. A Particle Strip comprises of linked groups of particles and the amount of these groups is defined by the strip's stripIndex attribute. Each particle with the same stripIndex attribute will a be part of the same strip, incrementing the stripIndex will create a new strip. This Block increments the Particle Strip's stripIndex attribute (unsigned integer) each time the start event of the Spawn Context triggers. This adds a new linked group of particles to the Particle Strip.

The stripIndex attribute returns to zero when a stop event triggers or if stripIndex reaches the **Strip Max Count**. This goes back to the first strip group index.

<video src="Images/Block-IncrementStripIndexOnStartExample.mp4" width="500" height="auto" autoplay="true" loop="true" title="A VFX Graph with an Increment Strip Index On Start Block, resulting in colorful particles spawning." controls></video><br/>A VFX Graph with an Increment Strip Index On Start Block, resulting in colorful particles spawning.

## Block compatibility

This Block is compatible with the following Contexts:

- [Spawn](Context-Spawn.md)

## Block properties

| **Input**           | **Type** | **Description**                                              |
| ------------------- | -------- | ------------------------------------------------------------ |
| **Strip Max Count** | uint     | The maximum value stripIndex can be. The range that stripIndex can be is between zero and this value minus one. |

## Remarks
This Block uses a VFXSpawnerCallback interface and you can use it as a reference to create your own implementation. The implementation for this Block is in **com.unity.visualeffectgraph > Runtime > CustomSpawners > IncrementStripIndexOnStart.cs**.