# IBM Visualization Data Explorer Programmer's Reference

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## 12.7 Field Construction

This section describes routines that aid in the construction of fields.

### Points and Dependent Data

Some Field components are often in one-to-one correspondence with the "positions" component (e.g., "data," "colors," "opacities," and surface "normals"). (Alternatively, any of these components may be in one-to-one correspondence with the "connections" component.) If they are in one-to-one correspondence with positions (indicated by a "dep" attribute of "positions"), then they are also expected to be the same size as the positions component. The following routines aid in constructing such components.

`Field DXAddPoint() Field DXAddColor(); Field DXAddFrontColor(); Field DXAddBackColor(); Field DXAddOpacity(); Field DXAddNormal();` `` Field DXAddPoints(); Field DXAddColors(); Field DXAddFrontColors(); Field DXAddBackColors(); Field DXAddOpacities(); Field DXAddNormals(); | Add points or point-dependent data to a Field. See DXAddPoint, ...Color, ...FrontColor, ...BackColor, ...Opacity, ...Normal,.
`Field DXAddFaceNormal() Field DXAddFaceNormals();` | Add connection-dependent normals to a Field. See DXAddFaceNormal, DXAddFaceNormals.

Note on Use
The fourteen routines listed above are all suitable for adding a small number of points or for rapid prototyping; but for better performance, see `DXAddArrayData()` in "Irregular Arrays".

### Connections

The routines listed here define the interpolation elements of a Field, creating a "connections" component with an appropriate "element type" attribute.

`Field DXAddLine() Field DXAddTriangle(); Field DXAddQuad(); Field DXAddTetrahedron();` | Add a single interpolation element to a Field. See DXAddLine, ...Triangle, ...Quad, ...Tetrahedron, ...Lines, ...Triangles, ...Quads, ...Tetrahedra.
`Field DXAddLines() Field DXAddTriangles(); Field DXAddQuads(); Field DXAddTetrahedra();` | Add interpolation element(s) to a Field. See DXAddLine, ...Triangle, ...Quad, ...Tetrahedron, ...Lines, ...Triangles, ...Quads, ...Tetrahedra.
`Field DXSetConnections()` | Sets the "connections" component of a Field as a specified Array with a specified element type. See DXSetConnections.
`Array DXGetConnections()` | Gets the "connections" component of a Field and checks to see if it has a specified "element type" attribute. See DXGetConnections.

### Standard Components

The following routines create and manipulate standard components of a Field.

`Field DXEndField()` | Creates the standard components that a Field is expected to contain if they do not already exist. See DXEndField.
`Error DXEndObject()` | Creates the standard components that Fields are expected to contain, sharing the results when components are shared between Fields. See DXEndObject.
`int DXEmptyField()` | Determines whether a Field contains information. See DXEmptyField.
`Field DXChangedComponentValues() Field DXChangedComponentStructure();` | Both routines delete all components of a Field that are derived from a specified component. `DXChangedComponentStructure()` also deletes all Field components that are dependent on or refer to a specified component. See Note on Use. See DXChangedComponentValues, DXChangedComponentStructure.

Note on Use
This example illustrates one use of `DXChangedComponentValues()`:
        g = DXCopy(f, COPY_STRUCTURE);
        a = DXGetComponentValue(g, "positions");
        b = ... modification of a ...
        DXSetComponentValue(g, "positions", b);
        DXChangedComponentValues(g, "positions");

`Object DXBoundingBox()` | Computes the bounding box of an Object. See DXBoundingBox.
`Array DXNeighbors()` | Returns the neighbors Array of a Field. See DXNeighbors.
`Error DXStatistics()` | Returns statistical information for an Object. See DXStatistics.
`Object DXValidPositionsBoundingBox()` | Computes the bounding box of the valid positions of an Object. See DXValidPositionsBoundaryBox.

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