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Enable AOI analysis
===================
Once [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) is [configured](configuration_and_execution.md) and [2D AOI are described](aoi_2d_description.md), fixation can be matched with AOI to build an AOI scan path before analyzing it.
## Add ArLayer to ArFrame JSON configuration
The [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer) class defines a space where to match fixations with AOI and inside which those matches need to be analyzed.
Here is an extract from the JSON [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) configuration file with a sample where one layer is added:
```json
{
"argaze.ArFeatures.ArFrame": {
"name": "My FullHD screen",
"size": [1920, 1080],
...
"layers": {
"MyLayer": {
"aoi_scene" : {
"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
}
}
},
"aoi_matcher": {
"argaze.GazeAnalysis.DeviationCircleCoverage.AOIMatcher": {
"coverage_threshold": 0.5
}
},
"aoi_scan_path": {
"duration_max": 30000
},
"aoi_scan_path_analyzers": {
"argaze.GazeAnalysis.Basic.AOIScanPathAnalyzer": {},
"argaze.GazeAnalysis.TransitionMatrix.AOIScanPathAnalyzer": {},
"argaze.GazeAnalysis.NGram.AOIScanPathAnalyzer": {
"n_min": 3,
"n_max": 5
}
}
}
}
}
}
```
!!! note
Timestamped gaze movements identified by the parent [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) are passed one by one to each [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer). So, the execution of all [ArLayers](../../argaze.md/#argaze.ArFeatures.ArLayer) is done during the parent [ArFrame.look](../../argaze.md/#argaze.ArFeatures.ArFrame.look) method call, as explained in the [previous chapter](configuration_and_execution.md).
Now, let's understand the meaning of each JSON entry.
### *layers*
An [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) instance can contains multiples [ArLayers](../../argaze.md/#argaze.ArFeatures.ArLayer) stored by name.
### MyLayer
The name of an [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer). Basically, it is useful for visualization purposes.
### *aoi_scene*
The set of 2D AOI into the layer as defined at [2D AOI description chapter](aoi_2d_description.md).
### *aoi_matcher*
The first [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer) pipeline step aims to match identified gaze movement with the layer's AOI.
The matching algorithm can be selected by instantiating a particular [AOIMatcher from the GazeAnalysis submodule](pipeline_modules/aoi_matchers.md) or [from another Python package](advanced_topics/module_loading.md).
In the example file, the chosen matching algorithm is the [Deviation Circle Coverage](../../argaze.md/#argaze.GazeAnalysis.DeviationCircleCoverage) which has one specific *coverage_threshold* attribute.
!!! warning "Mandatory"
JSON *aoi_matcher* entry is mandatory. Otherwise, the [AOIScanPath](../../argaze.md/#argaze.GazeFeatures.AOIScanPath) and [AOIScanPathAnalyzers](../../argaze.md/#argaze.GazeFeatures.AOIScanPathAnalyzer) steps are disabled.
### *aoi_scan_path*
The second [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer) pipeline step aims to build an [AOIScanPath](../../argaze.md/#argaze.GazeFeatures.AOIScanPath) defined as a list of [AOIScanSteps](../../argaze.md/#argaze.GazeFeatures.AOIScanStep) made by a set of successive fixations/saccades onto the same AOI.
Once gaze movements are matched to AOI, they are automatically appended to the AOIScanPath if required.
!!! warning "GazeFeatures.OutsideAOI"
When a fixation is not looking at any AOI, a step associated with an AOI called [GazeFeatures.OutsideAOI](../../argaze.md/#argaze.GazeFeatures.OutsideAOI) is added. As long as fixations are not looking at any AOI, all fixations/saccades are stored in this step. In this way, further analysis are calculated considering those extra [GazeFeatures.OutsideAOI](../../argaze.md/#argaze.GazeFeatures.OutsideAOI) steps.
This is particularly important when calculating transition matrices, because otherwise we could have arcs between two AOIs when in fact the gaze could have fixed itself outside in the meantime.
The [AOIScanPath.duration_max](../../argaze.md/#argaze.GazeFeatures.AOIScanPath.duration_max) attribute is the duration from which older AOI scan steps are removed each time new AOI scan steps are added.
!!! note "Optional"
JSON *aoi_scan_path* entry is not mandatory. If *aoi_scan_path_analyzers* entry is not empty, the [AOIScanPath](../../argaze.md/#argaze.GazeFeatures.AOIScanPath) step is automatically enabled.
### *aoi_scan_path_analyzers*
Finally, the last [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer) pipeline step consists of passing the previously built [AOIScanPath](../../argaze.md/#argaze.GazeFeatures.AOIScanPath) to each loaded [AOIScanPathAnalyzer](../../argaze.md/#argaze.GazeFeatures.AOIScanPathAnalyzer).
Each analysis algorithm can be selected by instantiating a particular [AOIScanPathAnalyzer from the GazeAnalysis submodule](pipeline_modules/aoi_scan_path_analyzers.md) or [from another Python package](advanced_topics/module_loading.md).
In the example file, the chosen analysis algorithms are the [Basic](../../argaze.md/#argaze.GazeAnalysis.Basic) module, the [TransitionMatrix](../../argaze.md/#argaze.GazeAnalysis.TransitionMatrix) module and the [NGram](../../argaze.md/#argaze.GazeAnalysis.NGram) module, which has two specific *n_min* and *n_max* attributes.
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