Hi there,
I wonder why we have some many form of curves in IGES? Can't type 126 more than enough to create a curve? Why we still need the 100, 104, or
108?
Form type in field 15 in the directory entry(DE) for type 126 has options:
0 - form of curve must be determined from the rational b spline parameters
1 - line
2 - circular arc
3 - elliptical arc
4 - parabolic arc
5 - hyperbolic arc
In order words, why iges provide the option in type 142 to have BPTR - pointer to the DE of the entity that contain the definition of the curve B in the parametric space (u,v) of the surface CPTR - pointer to the DE of the curve C
If we select 0 in type 126, then CPTR is NULL and type 100, 104 or 108 wont be necessary anymore.
I wonder if it is not always possible to intepret a curve using
126(rational b spline entity)?
what kind of curve in general not doing well if we use tpe 126?
please correct me if I am wrong.
thanks
julia