# Curves Module

Parent module: Geometry Module

group a3d_crv

Creates and accesses entities that represent geometric curves.

Geometric curves (A3DCrvBase) are a mandatory part of the topology construct in an A3DTopoBody entity. Do not confuse an A3DCrvBase entity with an A3DRiCurve entity. The latter is a particular representation item that has an A3DTopoSingleWireBody as its topology entry point.

All curves are defined as described in these steps:

1. Define the canonical form of the whole curve.

2. Define the actual parameterization and the portion of curve (trimming information) (A3DParameterizationData).

3. Define the orientation and scaling of the curve using a Cartesian transformation. The transformation cannot specify mirror or non-uniform scaling transformations (see A3DMiscCartesianTransformationData).

Here are definitions for terms that apply to curves.

• Curve is a mathematical description for a whole curve.

• Arc is a portion of a curve corresponding to an interval.

## Sub-modules

 NURBS Curve Entity type is kA3DTypeCrvNurbs . Linear Curve Linear Curve Circular Curve Circular Curve Elliptic Curve Elliptic Curve Parabolic Curve Parabolic Curve Hyperbolic Curve Hyperbolic Curve Polyline Curve Polyline Curve Composite Curve Composite Curve Equation Curve Equation Curve Transform Curve Transform Curve Curve On Surface Curve On Surface Offset Curve Offset Curve Helix Curve Helix Curve Intersection Curve Intersection Curve Blend02Boundary Curve Blend02Boundary Curve