如何在paper.js中绘制样条线

Question

I'm currently working on a project to display DXF files on a paper.js canvas. However, when I read the spline objects in the DXF file, I am completely confused by the naming and how I should translate them into paper.js curve objects.

DXF has: degree , control points and know values

Paper.js has: http://paperjs.org/reference/curve/

Here is an example of the DXF Spline data object :

controlPoints:(15) [{…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}],
degreeOfSplineCurve:5,
handle:"100",
knotValues:(21) [0, 0, 0, 0, 0, 0, 0.1, 0.2, 0.30000000000000004, 0.4, 0.5, 0.6, 0.7, 0.7999999999999999, 0.8999999999999999, 1, 1, 1, 1, 1, 1],
layer:"0",
numberOfControlPoints:15,
numberOfFitPoints:0,
numberOfKnots:21,
planar:true,
type:"SPLINE"

Let me know if you need more information

Answer 1

DXF curves are implemented as arbitrary degree Nonuniform rational B-splines (NURBS https://en.wikipedia.org/wiki/Non-uniform_rational_B-spline ), while paper.js supports only cubic bezier curves. In Paper.js a segment of bezier curve is defined with a point and handleIn and handleOut vectors. See http://paperjs.org/reference/segment/

NURBS is a more general representation than Bezier, so it might not be possible to present any NURBS with an exact bezier curve, but you can still find a close enough approximation of curve in DXF either using bezier curves or by using straight line segments.