4 Data Structures
TQ3NURBCurveData
data type. See "Creating and Editing NURB Curves," beginning on page 4-162 for a description of the routines you can use to create and edit NURB curves. Figure 4-18 shows a NURB curve.
typedef struct TQ3NURBCurveData { unsigned long order; unsigned long numPoints; TQ3RationalPoint4D *controlPoints; float *knots; TQ3AttributeSet curveAttributeSet; } TQ3NURBCurveData;order
The order of the NURB curve. For NURB curves defined by ratios of cubic B-spline polynomials, the order is 4. In general, the order of a NURB curve defined by polynomial equations of degree n is n+1. The value in this field must be greater than 1.numPoints
The number of control points that define the NURB curve. The value in this field must be greater than or equal to the order of the NURB curve.controlPoints
A pointer to an array of rational four-dimensional control points that define the NURB curve.knots
A pointer to an array of knots that define the NURB curve. The number of knots in a NURB curve is the sum of the values in theorder
andnumPoints
fields. The values in this array must be nondecreasing (but successive values may be equal, up to a multiplicity equivalent to the order of the curve).curveAttributeSet
A set of attributes for the NURB curve. The value in this field isNULL
if no NURB curve attributes are defined.
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