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# physicalWidth

An image’s width in centimeters.

## Discussion

This property informs the runtime how wide the image is in the physical environment. The runtime calculates the height based on the image’s aspect ratio.

Because this property describes a real-world width, the prim’s transform hierarchy doesn’t modify this property’s value.

### Declaration

```other
uniform double physicalWidth
```

### Define a reference image’s width

To recognize an image in the real world, the runtime requires a prim to specify how wide the image is in the physical environment.

```other
def Preliminary_ReferenceImage "ImageReference"
{
    uniform double physicalWidth = 12
    ...
}
```

---

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