Curve Output Options Panel for the COLLADA DAE File Exporter

This panel controls the output of 3D NURBS curves and 3D spline shapes.

Output independent 3D NURBS curves

The NuGraf/PolyTrans 3D database has a very extensive NURBS curve sub-system. Each NURBS curve object can have 1 or more NURBS curves associated with it. Multiple curves inside a single object can either be considered to form a single continuous "composite" curve, or each curve can be considered unique, closed, planar (in world space) and oriented such that the curves of the object can be directly converted into a trimmed NURBS surface (in other words, the first curve forms the boundary of the surface and subsequent closed curves form the holes).

The following options control how the various NURBS curve configurations can be converted during the export phase. An extensive internal NURBS curve conversion and cross-conversion system exists.

If 'renderable flag' enabled in NURBS curve primitive:

If the 'renderable' flag of a NURBS curve primitive is internally enabled, and the curve(s) form closed loops, then it is possible to convert the NURBS Curve primitive into a 3D format that is renderable: either a mesh or a Spline Shape. The following options define what will be done to NURBS Curves primitives during the export phase when their 'renderable' flag is enabled:

Convert and Output as Spline Shape

The NURBS Curve primitive will be converted into a corresponding Spline Shape primitive. The type of spline used will be taken from the "Spline curve output type" combo box.

Convert and Output as Polygon Mesh

The NURBS Curve primitive will be converted into a mesh object prior to export.

If 'renderable flag' not enabled:

If the 'renderable' flag of a NURBS Curve primitive is not enabled then the curves will be considered just as plain curves that cannot be seen when rendered. In this case, the following options define what will be done to NURBS Curves primitives during the export phase when their 'renderable' flag is disabled:

Convert and Output as a Spline Shape

The NURBS Curve primitive will be converted into a similar and corresponding Spline Shape primitive before export. The type of spline used will be taken from the "Spline curve output type" combo box. The 'renderable' flag of the Spline Shape will be disabled.

Convert and Output as a PolyLines

The NURBS Curve primitive will be converted into a 3D polyline primitive for output.

Output independent 3D spline shapes

The NuGraf/PolyTrans 3D database has a very extensive spline primitive sub-system. This primitive accommodates one or more spline curves per primitive. If the multiple spline curves are each closed then the overall Spline Shape is termed "renderable" and can be thus converted into a polygon mesh or a corresponding trimmed NURBS surface (patch). For example, the letter "B" can be defined by 3 Bezier curves, the first forming the outer boundary and the latter two forming holes. Note, that unlike the NURBS Curve primitive, each spline curve of the Spline Shape is composed of only a single curve segment (no composite spline curves are allowed).

The following options control how the various Spline Shape configurations can be converted during the export phase. An extensive internal Spline Shape conversion and cross-conversion system exists. The Spline Shape primitive also handles almost every major spline type (Bezier Spline, B-Spline, Cardinal Spline, Linear Spline, Tensioned Spline, TCB Spline), and their internal cross conversion (between spline types) or between the various spline types and a NURBS curve.

If 'renderable flag' enabled in spline shape primitive:

Convert and Output as Polygon Mesh

The Spline Shape primitive will be converted into a mesh object prior to export.

[No Change]

No change. The Spline Shape primitive will be exported as-is unless a specific spline type is chosen in the "Spline curve output type" combo box; if the current spline type is different than that shown in the combo box then the spline type will be changed (via resampling) prior to export.

If 'renderable flag' not enabled:

[No Change]

No change. The Spline Shape primitive will be exported as-is unless a specific spline type is chosen in the "Spline curve output type" combo box; if the current spline type is different than that shown in the combo box then the spline type will be changed (via resampling) prior to export.

Convert and Output as a Line Strips

Each spline curve of the Spline Shape primitive will be output as a COLLADA polyline.

Spline curve output type: Bezier Spline, B-Spline, Linear Spline

This drop-down box determines the type of spline which will be exported from the Spline Shape primitive. If the current spline type is different than the one chosen, then each curve of the Spline Shape will be resampled to the new spline type prior to export.