PolarDB:MESHGEOM

Structure overview

A MESHGEOM object consists of up to three components:

PATCH

PATCH holds one or more geometry objects. Separate multiple geometries with commas (,).

Supported geometry types:

• Point

• LineString

• Polygon

• MultiPoint

• MultiLineString

• MultiPolygon

• IndexSurface

• TriangleStrip

• TriangleFan

Example: two geometries in one PATCH

-- 2 patches: 1 Point and 1 IndexSurface
MESHGEOM(
  PATCH(
    POINT(0 0 1),
    INDEXSURFACE(VERTEX(0 0 1,0 10 2,10 10 3,10 0 4), INDEX((0,1,2),(1,2,3)))
  )
)

NORMAL

NORMAL holds a set of normal vectors for 3D points. Enclose each geometry object's coordinates in parentheses () and separate individual coordinates with commas (,).

The number of points in NORMAL must equal the number of vertices in the corresponding PATCH.

Example: PATCH with NORMAL and TEXCOORD

MESHGEOM(
  PATCH(
    TRIANGLESTRIP(0 0 1,0 10 2,10 10 3,10 0 4)
  ),
  NORMAL(
    (0 0 0, 1 1 1,2 2 2, 3 3 3)
  ),
  TEXCOORD(
    (0 0, 1 1, 2 2, 3 3)
  )
)

TEXCOORD

TEXCOORD holds a set of texture coordinates for 2D points. Enclose each geometry object's coordinates in parentheses () and separate individual coordinates with commas (,).

The number of points in TEXCOORD must equal the number of vertices in the corresponding PATCH.

TEXCOORD supports the Z and M dimensions. All patches in a MESHGEOM object must use the same dimensions.

Example: M dimension

-- All patches declare the M dimension
MESHGEOM(
  PATCH(
    POINT M(0 0 1),
    INDEXSURFACE M(VERTEX(0 0 1,0 10 2,10 10 3,10 0 4), INDEX((0,1,2),(1,2,3)))
  )
)

Reference another MESHGEOM object

MESHGEOM can reference geometry stored in another table. Use the following keywords to identify the source:

Enclose each keyword's value in at signs (@).

MESHGEOM(
  schema(@<schema_name>@),
  table(@<table_name>@),
  column(@<column_name>@),
  key(@<where_clause>@)
)

MESHGEOM(
  schema(@public@),
  table(@mytable@),
  column(@mycolumn@),
  key(@id=1@)
)