# Transparent and fixed boundariesΒΆ

Learning targets

- Specify different conditions at different boundaries of the computational domain

This geometry example specifies a rectangular computational domain with fixed boundary identifiers at the left and right side of the computational domain and transparent boundaries at the upper and lower side of the computational domain. This is a typical situation for light scattering simulations with periodic scattering objects (e.g., diffraction grating) where the size of the computational domain can be reduced by a factor of 2 when symmetry considerations about the geometry and the source are taken into account. The resulting geometry and mesh correspond to the following figure:

`.jcm`

Input File

layout.jcm [ASCII]

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Layout2D { Name = "GeometryTutorial2D/Grating" UnitOfLength = 1e-06 MeshOptions { MinimumMeshAngle = 20 MaximumSideLength = 1.2 } Objects { Polygon { Name = "ComputationalDomain/Background" DomainId = 1 Priority = -1 Points = [0 -1, 5 -1, 5 2.5, 0 2.5] Boundary { Number = [1 3] Class = Transparent } Boundary { Number = [2 4] BoundaryId = 1 } } Polygon { Name = "DielectricMaterial" DomainId = 2 Priority = 1 Points = [5 -1, 5 0, 1.5 0, 1 1.5, 0 1.5, 0 -1] } } }