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# imageSequenceInitialFrame

The index of the first frame in a particle image animation. Animatable.

```
var imageSequenceInitialFrame: CGFloat { get set }
```

## Discussion

To specify a sequence of frames for animating each particle, arrange the frames as a grid in a single image, as shown in [Figure 1](/documentation/scenekit/scnparticlesystem/1524153-particleimage#1965925). The total number of frames in an image sequence is the product of multiplying the [`imageSequenceRowCount`](/documentation/SceneKit/SCNParticleSystem/imageSequenceRowCount) and [`imageSequenceColumnCount`](/documentation/SceneKit/SCNParticleSystem/imageSequenceColumnCount) properties. Frames are numbered starting at zero, indicating the top left image in the grid.

When you use image sequences for particles, SceneKit interpolates between frames of animation, so a fractional value specifies a partial fade between two animation frames.

The default value is `0.0`, specifying that animation begins with the top left image in the grid.

You can animate changes to this property’s value. See [Animating SceneKit Content](/documentation/SceneKit/animating-scenekit-content).

---

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