Add an ArLayer ============== The [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer) class defines a space where to make matching of gaze movements and AOIs and inside which those matchings need to be analyzed. ![Empty layer area](../../img/ar_layer_empty.png) ## Add ArLayer to ArFrame JSON configuration file An [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) instance can contains multiples [ArLayers](../../argaze.md/#argaze.ArFeatures.ArLayer). Here is an extract from the JSON ArFrame configuration file with a sample where one layer is added: ```json { "name": "My FullHD screen", "size": [1920, 1080], ... "layers": { "MyLayer": { "aoi_scene" : { "upper_left_area": [[0, 0], [960, 0], [960, 540], [0, 540]], "upper_right_area": [[960, 0], [1920, 0], [1920, 540], [960, 540]], "lower_left_area": [[0, 540], [960, 540], [960, 1080], [0, 1080]], "lower_right_area": [[960, 540], [1920, 540], [1920, 1080], [960, 1080]] }, "aoi_matcher": { "DeviationCircleCoverage": { "coverage_threshold": 0.5 } }, "aoi_scan_path": { "duration_max": 30000 }, "aoi_scan_path_analyzers": { "Basic": {}, "TransitionMatrix": {}, "NGram": { "n_min": 3, "n_max": 5 } } } } } ``` !!! note Timestamped gaze movements identified by 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 parent [ArFrame.look](../../argaze.md/#argaze.ArFeatures.ArFrame.look) method call as explained in [previous chapter](ar_frame_configuration_and_execution.md). Now, let's understand the meaning of each JSON entry. ### "MyLayer" The name of the [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer). Basically useful for visualisation purpose. ### AOI Scene The [AOIScene](../../argaze.md/#argaze.AreaOfInterest.AOIFeatures.AOIScene) defines a set of 2D [AreaOfInterest](../../argaze.md/#argaze.AreaOfInterest.AOIFeatures.AreaOfInterest) registered by name. ![AOI Scene](../../img/ar_layer_aoi_scene.png) ### AOI Matcher The first [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer) pipeline step aims to make match identified gaze movement with an AOI of the scene. ![AOI Matcher](../../img/ar_layer_aoi_matcher.png) The matching algorithm can be selected by instantiating a particular [AOIMatcher](../../argaze.md/#argaze.GazeFeatures.AOIMatcher) from the [argaze.GazeAnalysis](../../argaze.md/#argaze.GazeAnalysis) submodule or [from another python package](advanced_topics/module_loading.md). In the example file, the choosen matching algorithm is the [Deviation Circle Coverage](../../argaze.md/#argaze.GazeAnalysis.DeviationCircleCoverage) which has one specific *coverage_threshold* attribute. !!! warning JSON *aoi_matcher* entry is mandatory. Otherwise, the AOIScanPath and AOIScanPathAnalyzers steps are disabled. ### AOI Scan Path The second [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer) pipeline step aims to build a [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 a same AOI. ![AOI Scan Path](../../img/ar_layer_aoi_scan_path.png) Once identified gaze movements are matched to AOI, they are automatically appended to the AOIScanPath if required. 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 JSON *aoi_scan_path* entry is not mandatory. If aoi_scan_path_analyzers entry is not empty, the AOIScanPath step is automatically enabled. ### AOI Scan Path Analyzers Finally, the last [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer) pipeline step consists in 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](../../argaze.md/#argaze.GazeFeatures.AOIScanPathAnalyzer) from the [argaze.GazeAnalysis](../../argaze.md/#argaze.GazeAnalysis) submodule or [from another python package](advanced_topics/module_loading.md).