﻿Surface.IsoCurve Method

Gets isoparametric curve.

Namespace:  Rhino.Geometry
Assembly:  RhinoCommon (in RhinoCommon.dll)
Syntax
```public Curve IsoCurve(
int direction,
double constantParameter
)```

#### Parameters

direction
Type: SystemInt32
0 first parameter varies and second parameter is constant e.g., point on IsoCurve(0,c) at t is srf(t,c) This is a horizontal line from left to right 1 first parameter is constant and second parameter varies e.g., point on IsoCurve(1,c) at t is srf(c,t This is a vertical line from bottom to top.
constantParameter
Type: SystemDouble
The parameter that was constant on the original surface.

#### Return Value

Type: Curve
An isoparametric curve or null on error.
Remarks
In this function "direction" indicates which direction the resulting curve runs. 0: horizontal, 1: vertical In the other Surface functions that take a "direction" argument, "direction" indicates if "constantParameter" is a "u" or "v" parameter.
Examples
```using Rhino;
using Rhino.DocObjects;
using Rhino.Commands;
using Rhino.Input;
using Rhino.Input.Custom;
using Rhino.Geometry;

namespace examples_cs
{
public class ExtractIsocurveCommand : Rhino.Commands.Command
{
public override string EnglishName
{
get { return "csExtractIsocurve"; }
}

protected override Result RunCommand(RhinoDoc doc, RunMode mode)
{
ObjRef obj_ref;
var rc = RhinoGet.GetOneObject("Select surface", false, ObjectType.Surface, out obj_ref);
if (rc != Result.Success || obj_ref == null)
return rc;
var surface = obj_ref.Surface();

var gp = new GetPoint();
gp.SetCommandPrompt("Point on surface");
gp.Constrain(surface, false);
var option_toggle = new OptionToggle(false, "U", "V");
Point3d point = Point3d.Unset;
while (true)
{
var grc = gp.Get();
if (grc == GetResult.Option)
continue;
else if (grc == GetResult.Point)
{
point = gp.Point();
break;
}
else
return Result.Nothing;
}
if (point == Point3d.Unset)
return Result.Nothing;

int direction = option_toggle.CurrentValue ? 1 : 0; // V : U
double u_parameter, v_parameter;
if (!surface.ClosestPoint(point, out u_parameter, out v_parameter)) return Result.Failure;

var iso_curve = surface.IsoCurve(direction, direction == 1 ? u_parameter : v_parameter);
if (iso_curve == null) return Result.Failure;

doc.Views.Redraw();
return Result.Success;
}
}
}```
```from Rhino import *
from Rhino.DocObjects import *
from Rhino.Commands import *
from Rhino.Input import *
from Rhino.Input.Custom import *
from Rhino.Geometry import *
from scriptcontext import doc

def RunCommand():
rc, obj_ref = RhinoGet.GetOneObject("Select surface", False, ObjectType.Surface)
if rc <> Result.Success or obj_ref == None:
return rc
surface = obj_ref.Surface()

gp = GetPoint()
gp.SetCommandPrompt("Point on surface")
gp.Constrain(surface, False)
option_toggle = OptionToggle(False, "U", "V")
point = Point3d.Unset

while True:
grc = gp.Get()
if grc == GetResult.Option:
continue
elif grc == GetResult.Point:
point = gp.Point()
break
else:
return Result.Nothing

if point == Point3d.Unset:
return Result.Nothing

direction = 1 if option_toggle.CurrentValue else 0
b, u_parameter, v_parameter = surface.ClosestPoint(point)
if not b: return Result.Failure

iso_curve = surface.IsoCurve(direction, u_parameter if direction == 1 else v_parameter)
if iso_curve == None:
return Result.Failure

doc.Views.Redraw()
return Result.Success

if __name__ == "__main__":
RunCommand()```
Version Information

#### Rhino for Mac

Supported in: 5.4

#### Rhino for Windows

Supported in: 6.5