Introduction
In this chapter we'll cover the NURBS rendering functionality of V-Ray. NURBS stands for Non-uniform rational Basis spline.
Parameters
The plugins which we're interested in this chapter are GeomStaticNURBS and NURBSCurve.
GeomStaticNURBS
- cvs - List of lists with the control vertices of the NURBS.
- weights - List of lists with the weights for the NURBS's CVs in the corresponding cvs list.
- trims - List of TrimmingRegion objects (there's a plugin for them). The orientation is used to determine whether the trim will generate geometry inside of it or outside of it
- listTrimCurves - List of NURBSCurve objects - the trimming curves
- trimsComplex - A single plug-in containing all the trim information.
- uKnots - List of floats with knot values in the U direction.
- vKnots - List of floats with knot values in the V direction.
- maxSubdivDepth - this parameter controls the maximum number of triangles that V-Ray is allowed to generate for this NURBS surface. Note that this number is proportional to the logarithm of the actual number of triangles, so you don't need very high values. Also if you want to lower the quality of the NURBS surfaces, it is better to do this by increasing the Curvature threshold (
flatnessCoef) parameter, rather than lowering this one. - flatnessCoef - decrease this parameter to allow V-Ray to subdivide the NURBS surface more, for a smoother result. Increase it for faster rendering and less RAM usage, but lower quality.
- regularSubdiv - Default value: false
- regularUSteps - Default value: 20
- regularVSteps - Default value: 20
- uDirectionType - Type of the U direction.
- vDirectionType - Type of the V direction.
- uDegree - Degree of the spline in the U direction.
- vDegree - Degree of the spline in the V direction.
- flipNormals - If true, invert the directions of the normals
- generateStatic - when on, V-Ray will subdivide the NURBS surface into triangles before the actual rendering has begun. This allows the building of a faster BSP tree but takes more memory. When off, NURBS surfaces will be treated as dynamic geometry, similar to Subdivision meshes, and will be converted into triangles on the fly. This saves memory for other purposes, but may be slower.
- primary_visibility - Whether this geometry is visible to primary camera rays
- reference_nurbs - The reference nurbs object which is used to calculate the uvw coordinates when a 3d placement is used.
- reference_transform - The transform of the reference nurbs object.
NURBSCurve
- degree - Degree of the curve
- cvs - The control vertices of the curve
- knotVector - The knots vector for the curve
- boundary - Mark curve as island or hole
Example
The following example is rendered using this scene.
