Use NURBS in SharpGL

Question

I wrote a program to display some pressure-measurements. I want to use NURBS for a detail visualisation. So I orientated me to enter link description here

My field has a range of 40x48 squares. So 40 rows and 48 columns. The Z component(the height) should be variable.

But I don't understand how to define

glMap2f(GL_MAP2_VERTEX_3, 0, 1, 3, 4, 0, 1, 12, 4, &ctrlpoints[0][0][0]);

// Parameter:
        //   target:
        //     What the control points represent (e.g. MAP2_VERTEX_3).
        //
        //   u1:
        //     Range of the variable 'u'.
        //
        //   u2:
        //     Range of the variable 'u.
        //
        //   ustride:
        //     Offset between beginning of one control point and the next.
        //
        //   uorder:
        //     The degree plus one.
        //
        //   v1:
        //     Range of the variable 'v'.
        //
        //   v2:
        //     Range of the variable 'v'.
        //
        //   vstride:
        //     Offset between beginning of one control point and the next.
        //
        //   vorder:
        //     The degree plus one.
        //
        //   points:
        //     The data for the points.

I don't know how to set the parameters in my case. For example what is u1 and u2? OR what are my ControlPoints?

Answer 1

In this link you can find a more detailed description of the parameters:

https://msdn.microsoft.com/en-us/library/windows/desktop/ee872053(v=vs.85).aspx

In your surface X direction is given by u-coordinate and Y direction is given by v-coordinate. It is common to set u1-u2 and v1-v2 to the [0,1] interval.

The order of the surface is interpolated between points (you can do linear interpolation with order=1, quadratic interpolation with order=2 and so on. 2 or 3 should be ok for your needs.

With this said, I am afraid that the method "glMap2f" will not accurately represent your data as in general the "control points" are not on the surface itself (as shown in the following )

You have to look for an algorithm to interpolate a nurbs surface from a point cloud, and then use glMap2f with the control points calculated.

If you want to know more about Nurbs, look for "The Nurbs book" from L. Piegl