How can i get Geom_Surface's UV parametric surface function?

[NFYG]

def read_step(filepath):

    compound = read_step_file(filepath)
   
    topo = TopologyExplorer(compound)

    
    for i,face in enumerate( topo.faces() ):

        geom_surface = BRep_Tool().Surface(face)

        print(geom_surface.Bounds())

I use such code to access every face of my *.STEP file.

How can i get geom_surface's UV parametric surface function?

And why the surface is infinite while my *.STEP file is finite and bounded? （geom_surface.Bounds() return infinite U1 U2 V1 V2）

[Squirrel8475]

I am just a pyOCC enthusist, not involved in the development, but I think it is because the surface described at Geom level generates u,v patches. You can only do operations along iso-u or iso-v (shorten, expand for instance).

In case something more complicated is needed (like some cuts in arbitrary direction for instance, or a hole), it needs to be handled at the TopoDS level. The TopoDS level associates the base surface from the Geom level, and the way to modify it. The combination of both is the TopoDS level. So strictly speaking you cannot convert a TopoDS surface to a Geom surface, you can just get back which base surface was used in combination with the modifiers.

See : #1340