geometry/legacy/layers.md

0001 # Layer classes
0002
0003 The {class}`Acts::Layer` class is an extension of the {class}`Acts::Surface` class that allows the
0004 definition of sub surfaces (sensitive surfaces for modules, or extra material
0005 surfaces).
0006
0007 The layer can simply correspond to a 'virtual' surface in the detector
0008 description or represent a more complex object that may contain:
0009
0010 * a representing surface, which is accessible via a {func}`Acts::Layer::surfaceRepresentation`
0011 * an array of contained surfaces, accessible via {func}`Acts::Layer::surfaceArray` method
0012 * approach surfaces (i.e. boundary surface of the volume occupied by the layer)
0013 * surface material description on any of the confined surfaces
0014
0015 The following illustration shows an $xy$ view of a cylinder layer with planar
0016 detection modules:
0017
0018 ![CylinderLayer](../figures/CylinderLayer.png)
0019
0020 Modules can be sorted onto layer using all supported binning methods described
0021 through the {class}`Acts::SurfaceArray` class. The binning can be adjusted to fit as well as
0022 possible.
0023
0024 ![DiscLayerEB](../figures/DiscLayerEB.png)
0025
0026 The unoccupied space in a volume that contains a layer array is filled with
0027 objects of type {class}`Acts::NavigationLayer`, which allows that in a fully static geometry
0028 setup, every single point in a volume can be associated with a layer. Layer
0029 objects are confined together in a special {type}`Acts::LayerArray` class and can be
0030 contained by a {class}`Acts::TrackingVolume`.
0031
0032 ![LayerArray](../figures/LayerArray.png)