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Describe 2D AOI
================
Once [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) is [configured](configuration_and_execution.md), [areas of interest (AOI)](../../argaze.md/#argaze.AreaOfInterest.AOIFeatures.AreaOfInterest) need to be described to know what is looked in frame.
According to common computer graphics coordinate convention, all AOI need to be described from a top left frame corner origin with a coordinate system where:
* +X is pointing to the right,
* +Y is pointing downward.
!!! warning
All AOI spatial values must be given in **pixels**.
### Edit SVG file description
SVG file format could be exported from most vector graphics editors.
``` xml
<svg>
<path id="GeoSector" d="M860,160L1380,100L1660,400L1380,740L1440,960L920,920L680,800L640,560L860,160Z"/>
<rect id="LeftPanel" x="0" y="0" width="350" height="1080"/>
<circle id="CircularWidget" cx="1800" cy="120" r="80"/>
</svg>
```
Here are some common SVG file features needed to describe AOI:
* *id* attribute indicates an AOI name.
* *path* element describes any polygon using only [M, L and Z path intructions](https://www.w3.org/TR/SVG2/paths.html#PathData)
* *rect*, *circle* and *ellipse* allow, respectively, to describe rectangular, circular and elliptic AOI.
### Edit JSON file description
JSON file format allows describing AOI.
``` json
{
"GeoSector": [[860, 160], [1380, 100], [1660, 400], [1380, 740], [1440, 960], [920, 920], [680, 800], [640, 560]],
"LeftPanel": {
"Rectangle": {
"x": 0,
"y": 0,
"width": 350,
"height": 1080
}
},
"CircularWidget": {
"Circle": {
"cx": 1800,
"cy": 120,
"radius": 80
}
}
}
```
!!! note ""
Now we have AOI description, read the next chapter to learn [how to enable AOI analysis](./aoi_analysis.md).
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