LineObject* spline_linear = spline->GetLineObject(document, precision);
Works like a charm. The closer float "precision" to one the better the approximation, as far as I understand.
One thing, that confuses me is that new object appear in c4d menus with little white"question mark" sign (see picture).
I don't undersytand why.
Here is my piece of code:
LineObject* spline_linear = spline->GetLineObject(document, 0.9);
document->InsertObject(spline_linear, NULL, NULL, 0); // Add it to the OM
Oh, I see. Now I can extract all the points from this LineObject and construct a simple linear spline if I need one.
I guess cinema4d doesn't recognize the LineObject. Hence, question mark in menus.