Need to increase control point density for surface



Where can I increase the default value of the number of control points that appear for a surface when one selects surface and hits F10 ?

I have a diagonal edge and need to pull the surface formed by patch down tighter to it, or can I increase the density just parallel to and in the area of the edge. Rest of surface is parallel to the control point grid but using those I have at that edge sees a bad ripple occur when being pulled in.



Control points are an intrinsic part of the surface structure (like curve control points) and unlike the isocurve display, one cannot simply “add density”. What you can do:

  1. Rebuild the surface with more points in one direction or both. That
    MAY change the surface significantly elsewhere however, depending
    on the surface configuration and number of points.

  2. Add knots or rows of control points locally : with the commands
    InsertKnot and/or InsertControlPoint you can add knots or rows of
    control points to a surface locally where you need more
    "flexibility" without radically changing the surface further away.
    You need to choose the direction (u or v) for the additional row(s).



I had wondered on insertKnot, best to do this after all other tweaking doen as one ends up with a lot more control points to push and pull elsewhere as a result.

What is the difference between InsertKnot and InsertControlPoint as they seem to give me the same extra points and lines.



Depending on the surface, InsertKnot may not give you a line of control points exactly where you insert the knot…


(Pascal Golay) #5

InsertKnot does not change the shape of the curve or surface at all. On the other hand, it will rearrange rows of points, including the new one added with the knot, to make this happen. Except in special cases, knots will not be at the same locations as control points- i.e. you cannot choose where the new points will go, exactly.
InsertControlPoint inserts points exactly where you put them, but except in special cases will change the shape of the curve or surface… a little, or a lot. Currently, The output from InsertControlPoint always has uniform knots.



@pascal Thank you for that precise description and another bit of knowledge to be stored in the repository for future use… The repository seems to be getting more crowded these days, probably a consequence of more and more things to store as well as the storage space that is continually diminishing… :neckbeard:

(Pascal Golay) #7

I have a different metaphor for what I assume is the same phenomenon- I think of it as the ‘sieve effect’…