This topic provides a reference table for all automatic type conversions to curve, sorted by merit.
Direct Conversions
This section lists all direct 
conversions to the curve type. A 'Direct' conversion indicates a relation between very related types, such as integers and numbers, or 2D and 3D points. Though note that even these conversions can fail due to out-of-bounds issues, or be narrowing due to reduction.
| From | Explanation |
|---|---|
| arc | Converts the arc into a curve representation. |
| circle | Converts the circle into a curve representation. |
| line | Converts the line into a curve representation. |
| polyline | Converts the polyline into a curve representation. |
| rectangle | Converts the rectangle into a curve representation. |
| region | Extracts the outer boundary curve of the region. |
| triangle | Converts the triangle into a curve representation. |
Plausible Conversions
This section lists all plausible 
conversions to the curve type. A 'Plausible' conversion indicates a non-straightforward, but a still reasonable conversion between two types that share a salient quality, or where one is an obvious sub-type of the other. For example curves and intervals, or points and planes. Any plausible conversion can also be achieved through the explicit use of standard components.
| From | Explanation |
|---|---|
| box | Extracts the base outline curve of the box. |
| brep | Extracts the naked edge curves of the boundary representation. |
| identifier | Duplicates the referenced Rhino curve object. |
| mesh | Extracts the naked edges of the mesh. |
| sphere | Extracts the equatorial curve of the sphere. |
| SubD | Extracts the naked edge curves of the subdivision surface. |
| surface | Extracts the edge curves of the surface. |
| tube | Extracts the base circle curve of the tube. |