Zachrkn

In an effort to better understand nurbs, I created a nurbs object which is basically a 2d plane with a single column of control points being "elevated" in the Z plane (or with multiple consecutive columns being elevated). An immediate problem appears - different rows seem to have different "elevations." Turning on ctlshow demonstrates that the control points are not the problem; they are all equidistant. The mesh, for some reason I cannot understand, goes to a different "elevation" for each column.

I'm guessing the problem has something to do with the way these values are interpolated. From this post, 

https://cycling74.com/forums/linear-control-matrix-grid-in-nurbs,

 the contributors have suggested that setting Order to 1 1 would fix the problem, but it does not.

Below I've pasted in a slightly modified version of Recipe 18 from the 2nd Jitter Recipe book (thanks Andrew!!) It's clear from this that as we go through a nurbs object elevating the various columns, the outcome of the z-plane interpolation is different depending on where the columns are in the object. It's also interesting to note that if the dimensions of an object are, say, 5x5x2 control points and two consecutive columns are elevated, the problem does not manifest (although they do manifest if just a single column is elevated). But if the dimensions are upped to 25x25x2, the two consecutive columns no longer "even out" with interpolation.

Does anyone either see what I'm doing wrong or is able to explain the math behind the nurbs object so I can understand why this is happening?

In an effort to better understand nurbs, I created a nurbs object which is basically a 2d plane with a single column of control points being "elevated" in the Z plane (or with multiple consecutive columns being elevated).  An immediate problem appears - different rows seem to have different "elevations."  Turning on ctlshow demonstrates that the control points are not the problem; they are all equidistant.  The mesh, for some reason I cannot understand, goes to a different "elevation" for each column.

I'm guessing the problem has something to do with the way these values are interpolated.  From this post, https://cycling74.com/forums/linear-control-matrix-grid-in-nurbs, the contributors have suggested that setting Order to 1 1 would fix the problem, but it does not.  

Below I've pasted in a slightly modified version of Recipe 18 from the 2nd Jitter Recipe book (thanks Andrew!!)  It's clear from this that as we go through a nurbs object elevating the various columns, the outcome of the z-plane interpolation is different depending on where the columns are in the object.  It's also interesting to note that if the dimensions of an object are, say, 5x5x2 control points and two consecutive columns are elevated, the problem does not manifest (although they do manifest if just a single column is elevated).  But if the dimensions are upped to 25x25x2, the two consecutive columns no longer "even out" with interpolation.

nurbs-mesh-vs-control-points-problem

Bumping after 1 week in the hope that someone may know the answer to this or show me where I'm screwing up. Thanks again!

Bumping after 1 week in the hope that someone may know the answer to this or show me where I'm screwing up.  Thanks again!


Nurbs mesh vs control points problem