The coord field defines a grid of regularly spaced coordinates in 3D Cartesian space. The number of entries in the coord field depends on its LatticeCoordType, which has valid values of LATTICE_COORD_UNIFORM and LATTICE_COORD_RECTLINEAR. If the LatticeCoordType is LATTICE_COORD_UNIFORM, only the minimum and maximum values of the XYZ coordinate data are stored in the coord field. Thus, there are six entries in this field arranged in the following order: minimum X value, maximum X, minimum Y, maximum Y, minimum Z, and maximum Z.

If the LatticeCoordType is LATTICE_COORD_RECTLINEAR, the data stored in the coord field consists of all X coordinates followed by all Y coordinates followed by all Z coordinates.

Working in conjunction with the coord field is the dimension field. It specifies the number of grid points in each of the three dimensions (X, Y, and Z). The following example, which works just in the X dimension, shows how these two fields work together.

The following settings:

represent the following X coordinates:

1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0

If the coord field is set to LATTICE_COORD_RECTLINEAR, to represent the same X coordinates, the first entry in the dimension field would again be 10, but the first 10 entries of the coord field would be the values:

1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0

In general, the only time you would use LATTICE_COORD_RECTLINEAR is when the grid points are not spaced equally along one or more of the axes. If the spacing is uniform in all 3 dimensions, the amount of storage space for the coordinates can be significantly reduced by using LATTICE_COORD_UNIFORM.

The data field holds a pointer to the data located in ChemLattice3's 3D grid. For more information, see “Setting Values in the ChemLattice3 Data Field.”

At each grid point defined by the coord and dimension fields, there are one or more sets of data. The data might be, for example, the value of the electron density, as calculated at each point in the 3D grid. The nDataVar tells how many sets of data are stored at each grid point, for example, each grid point might store values for electron density and electrostatic potential. The type of data that can be stored in a ChemLattice3 is given by the LatticeDataType enum, as shown below.

enum LatticeDataType {
    LATTICE_DATA_INT8,
    LATTICE_DATA_INT16, 
    LATTICE_DATA_INT32,
    LATTICE_DATA_FLOAT32,
    LATTICE_DATA_FLOAT64,
    LATTICE_DATA_BAD_TYPE,
};

Each of these values defines the number of bits used to store the data and whether the data is of type integer or floating point. If there is more than one set of data at a grid point, the data must all be of the same LatticeDataType and the data is stored in an interleaved manner. For example, if each grid point stores values for electron density and electrostatic potential, the data field would be organized in the following manner:

data[0]  ==  electron_density[0]
data[1]  ==  electrostatic_potential[0]
data[2]  ==  electron_density[1]
data[3]  ==  electrostatic_potential[1]

Unlike most other Open Inventor and Molecular Inventor fields, the data field is a pointer to a standard Open Inventor multiple-valued field type. Because it is a pointer, it is referenced differently than the other fields. For example, suppose an instance of ChemLattice3 was generated with the following line:

ChemLattice3 *theLattice =
    new ChemLattice3(LATTICE_DATA_FLOAT32, LATTICE_COORD_UNIFORM);

To set the value of the first (number 0) entry in the data field, the code would look like this, where value is the floating point number you wish to store in the data field::

((SoMFFloat *)(theLattice->data))->set1Value(0, value);

In the case where two values are stored in the data field for every grid point, set the values in the following way:

((SoMFFloat *)(theLattice->data))->set1Value(0, electron_density[0]);
((SoMFFloat *)(theLattice->data))->set1Value(1, electrostatic_potential[0]);
((SoMFFloat *)(theLattice->data))->set1Value(2, electron_density[1]);
((SoMFFloat *)(theLattice->data))->set1Value(3, electrostatic_potential[1]);

If the antiAlias field is set to TRUE, the contour lines are rendered using anti-aliasing.

If the iAxis field is set to TRUE, contour lines along the X axis and in the YZ plane are generated. If the jAxis field is set to TRUE, contour lines along the Y axis and in the XZ plane are generated. If the kAxis field is set to TRUE, contour lines along the Z axis and in the XY plane are generated.

If the ChemLattice3 instance specified in the lattice field contains more than one set of data, the dataVar field specifies which set of data should be used to generate the contour lines.

The levels field specifies the values in the ChemLattice3 instance through which the contour lines should be drawn. For example, if the ChemLattice3 instance specified in the lattice field contains electron density data, levels can be set to generate three sets of contour lines representing the locations where the values of electron density are 0.5, 0.75, and 1.0 electrons per cubic angstrom.

If the orderedRGBA field is not NULL and the number of colors in the orderedRGBA field matches the number of values in the levels field, the contours are colored by the values in orderedRGBA.

The orderedRGBA field specifies the colors used to render the contour lines. If the orderedRGBA field is not NULL and the number of colors in the orderedRGBA field matches the number of values in the levels field, the contours are colored by the values in orderedRGBA.

The lattice field is an instance of ChemLattice3 that contains the data through which the contour lines are drawn. If there is more than one set of data in the ChemLattice3 instance, set the dataVar field to the set of data you want to display using contour lines.

The following sections describe the fields in ChemContour2.

The following sections describe the fields in ChemIso.