Open Source Seamless3d 2.127 (including French and English versions) is available for download from:
A new specialised build node, the NurbsLathe
has been added for 2.127.
To see this node in action just create a new smls file, select the part node and click on the NurbsLathe
icon in the main (horizontal) toolbar.
Like the BezierLatheBuild
node is dead simple to use even if you have never used Seamless3d before.
Like the BezierLathe you simply drag the control points in only 2 dimensions to create a curved shape.
To insert a new control point after the selected control point, increment the point's length field.
To delete the selected control point decrement the point's length field.
The NurbsLathe not only offers instant gratification for beginners it is also good for setting up a NurbsPatch
To convert a NurbsLathe
to a NurbsPatch
right click on the NurbsLathe icon in the scene tree and select "convert to patch".
The shape will be exactly the same as when it was a lathe but a patch allows us to carry on making a more advanced shape than is possible from a lathe.
The prismSides field is only used for converting to a patch, it specifies the number of flat sides for the patch's control prism.
Unlike the BezierLathe node there is no fix field for creating a new segment because Nurbs only need one segment due to the fact that the control points only affect the curve near by.
I have much better understanding in how beziers compare to Nurbs now that a little over a year has passed since I added the first BezierLathe to seamless.
I remember being a little confused by which was easier to control, Beziers or Nurbs.
This depends on the task.
Nurbs are easier in the sense that the control points are closer to the curve they affect and because you can add more control points without them affecting all of the curve but because the control points for a Bezier influence the entire curve with in a segment they are easier to control than Nurbs to make a smooth curve when the curve is within a segment and when the curve does not need to curve in and out more than a small number of times.
Beziers are great for making perfect continuous "sexy" curves but soon as you need a new segment in order to make a more complex curve all the virtue of using a Bezier is lost leaving Nurbs with more attractive properties.
Even with the tangent being matched between the 2 Bezier segments, the human eye can typically see where one curve comes to an end and where a new one begins at the exact point where the 2 segments join. This is because the control points between the 2 segments are completely isolated from each other where as with Nurbs, although the control points only affect the curve locally there is always an overlapping influence from a number of control points at any point within the curve and so the human eye can not detect a single point where one lot of control points begin and where another lot end.
In comparing Nurbs to Beziers confusion can arise from the fact that Nurbs can be set up to generate Bezier curves with the same strengths and weakness Beziers have that I have just described.
In comparing Nurbs to Beziers I am referring to Nurbs where they are set to have the control points only affect the curve locally which is how Nurbs are most often used.
A bug that caused unexpected behaviour when dragging the control points for the BezierLathe when the scale field was not set to the default value has been found and fixed for 2.127 as well as some other bugs unrelated to the NurbsLathe.
Many thanks to the program White Dune which was a great help to me when experimenting with Nurbs and many thanks to MUFTI one of the White Dune programmers who suggested I try White Dune