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POLYGON

Define a volume as the intersection of one, two, or three polygons in the coordinate planes. Each polygon is extruded along the unused axis (XY along \(z\), XZ along \(y\), YZ along \(x\)). A coordinate plane that is omitted is treated as infinite.

By default a cell is included if its center lies in every defined extrusion. See Polygon in the Theory Guide.

Required Cards:

POLYGON

Opens the POLYGON block within a REGION block.

Within the POLYGON block, one or more of:

XY

Vertices of a polygon in the XY plane. Two points define an axis-aligned rectangle. \(N > 2\) points define a simple polygon and must be listed clockwise or counter-clockwise without repeating the first vertex. The unused coordinate (\(z\)) is required on each line and is ignored. At most 100 vertices.

XY
  x0 y0 z0
  x1 y1 z1
  x2 y2 z2
  ...
  xN yN zN
/

XZ

Same as XY, but in the XZ plane (unused coordinate is \(y\)).

YZ

Same as XY, but in the YZ plane (unused coordinate is \(x\)).

Optional Cards:

TYPE <string>

How the volume is mapped onto the grid.

CELL_CENTERS_IN_VOLUME

Default. Include a cell if its center lies in every defined extrusion. Cell-body intersection is not tested. All grid types.

BOUNDARY_FACES_IN_VOLUME

Include boundary faces whose centroids lie in the volume. Implicit unstructured grids only.

Examples

REGION polyvol_xy
  POLYGON
    XY
      1. 1. 0.
      1. 2. 0.
      2. 2. 0.
      2. 4. 0.
      3. 4. 0.
      3. 2. 0.
      4. 2. 0.
      4. 1. 0.
    /
    XZ
      0. 0. 3.
      5. 5. 4.
    /
  /
END


REGION pond
  POLYGON
    TYPE BOUNDARY_FACES_IN_VOLUME
    XY
      1081.09 512.609 0.
      1008.38 536.404 0.
      957.98 554.706 0.
      904.05 562.406 0.
      817.357 580.904 0.
      734.512 585.373 0.
      683.75 579.356 0.
      605.18 536.218 0.
      585.15 490. 0.
      638.527 440.49 0.
      704.511 387.615 0.
      775.457 384.037 0.
      860.4 401.267 0.
      950.316 432.744 0.
      1015.65 472.986 0.
    /
    XZ
      0. 0. 1.
      1126. 0. -22.
    /
  /
END