Surface parameterization

Rhino Developer
1

Hi,

In RhinoCommon we can set domain to a surface e.g.
surface.SetDomain(0, new Interval(0, 1));

Is there a backwards operation to retrieve original domain before normalizing it?

2

I think this is what you’re looking for:

https://developer.rhino3d.com/api/RhinoCommon/html/M_Rhino_Geometry_Surface_Domain.htm

domain
domain960Ă—1041 79.4 KB

-Kevin

3

Nope, if a surface is already normalized, this returns [0-1].
I am wondering how the initial domain is computed.

4

Depending on what you want to do, you could probably just store its domain in a temporary variable, before reparametrizing it.

5

Hi @Petras_Vestartas,

You should not need to normalize the domain of curves and surfaces.

I’m sure I’ve posted this before:

–

Poorly parameterized objects may not intersect and trim properly when combined with other objects. “Poorly parameterized” means the curve’s domain or the surface’s u or v spaces are tiny or huge compared to the size of the object.

When curves and surfaces are paramterized with a [0,1] domain, both the accuracy and the precision of geometric calculations like intersections and closest points are reduced, sometimes dramatically. Ideally the domain of a curve is close to it’s length and the domains of a surface is close to is average breadth in the appropriate direction.

We try to have parameterization match the length of a curve or some measure of the width of the surface. Derivative information is better if we do it this way.

–

To convert interval value to normalized parameter, use Interval.NormalizedParameterAt.

To convert normalized parameter to interval value, use Interval.ParameterAt.

– Dale

1 Like
6

Hi @Petras_Vestartas, from the size of the surface eg. try like below:

import Rhino
import scriptcontext
import rhinoscriptsyntax as rs

def DoSomething():
    
    brep_id = rs.GetObject("Surface", rs.filter.surface, True, False)
    if not brep_id: return
    
    # for single faced breps only
    brep = rs.coercebrep(brep_id, True)
    if brep.Faces.Count != 1: return
    
    rc, width, height = brep.Faces[0].UnderlyingSurface().GetSurfaceSize()
    if rc:
        interval_u = Rhino.Geometry.Interval(0, width)
        interval_v = Rhino.Geometry.Interval(0, height)
        brep.Faces[0].SetDomain(0, interval_u)
        brep.Faces[0].SetDomain(1, interval_v)
        scriptcontext.doc.Objects.Replace(brep_id, brep)
        
DoSomething()

it should give equal results like using _Reparameterize _Automatic on a surface.

_
c,

7

@clement This Indeed answers my questions. Thank you.

Also thank you @dale I was always setting domain to 0-1 without too much thinking, which seems not be a good practice.

@diff-arch Thank you too.