Points in Python
This guide provides an overview of the RhinoScriptSyntax Point Geometry in Python.
In Python, a Rhino 3D point is represented as a Point3d structure. Conceptually, Point3d exist in memory as a zero-based list containing three numbers. These three numbers represent the X, Y and Z coordinate values of the point.
point3D contains [1.0, 2.0, 3.0]
A Point3D structure can be constructed in a number of different ways. Two common ways are:
import rhinoscriptsyntax as rs pnt = rs.CreatePoint(1.0, 2.0, 3.0) pnt = rs.CreatePoint(1.0, 2.0) # This creates a point with the Z coordinate set to 0
A point list can also be constructed one element at a time:
The ‘CreatePoint()’ function is very flexible. It can take a list or tuple of two or 3 numbers and return a Point3d. The function can also extract the coordinates of a Rhino GUID to return a Point3D.
It is not always necessary to construct a point before passing it to a function that requires a point. It is possible to construct points directly as an argument to a function. A Point is a list like structure. Wrap coordinates in brackets
 when passing them directly to a function. For instance the
rs.addline(point, point) function requires two points. Use the following syntax to construct the points on the fly:
Like 3-D points, Python represents a single 2-D point as a zero-based list of numbers. The difference being that 2-D points contain only X and Y coordinate values.
Passing coordinates in
 to a function is common with RhinoScriptSyntax.
Accessing Point Coordinates
A Point3D list can be accessed like a simple python list, one element at a time:
import rhinoscriptsyntax as rs pnt = rs.CreatePoint(1.0, 2.0, 3.0) print(pnt) #Print the X coordinate of the Point3D print(pnt) #Print the Y coordinate of the Point3D print(pnt) #Print the Z coordinate of the Point3D
The coordinates of a Point3d may also be accessed through its .X, .Y and .Z properties.
import rhinoscriptsyntax as rs pnt = rs.CreatePoint(1.0, 2.0, 3.0) print(pnt.X) # Print the X coordinate of the Point3D print(pnt.Y) # Print the Y coordinate of the Point3D print(pnt.Z) # Print the Z coordinate of the Point3D
Using Python’s ability to assign values to multiple variables at one, here are is a way to create x, y, and z variables all at once:
x, y, z = rs.CreatePoint(1.0, 2.0, 3.0) # or # x, y, z = rs.PointCoodinate(point)
To change an individual coordinate of a Point3d simply assign a new value to the correct coordinate through the index location or coordinate property:
import rhinoscriptsyntax as rs pnt = rs.CreatePoint(1.0, 2.0, 3.0) pnt = 5.0 # Sets the X coordinate to 5.0 pnt.Y = 45.0 # Sets the Y coordinate to 45.0 print(pnt) #Print the new coordinates
Using the Python
for function it is quite easy to walk through each coordinate in succession:
for c in pnt: print c # This will loop through each coordinate in the point3d
Rhinoscriptsyntax contains a number of methods to manipulate points. See RhinoScript Points and Vectors Methods for details.
For those familiar with RhinoScript, which represents points as a pure list, the Python representation is a little different and offers a few more options.
Adding a point to display in Rhino
It is important to understand the difference between a Point3d and a point object added to Rhino’s document. Any geometry object that exists in Rhino’s database is assigned an object identifier. This is represented as a Guid. The Guid’s object is something that can be drawn, belongs to a layer, is saved to a Rhino file and is counted as a Rhino object. A Point3d is simply a structure of 3 numbers that exists in memory. It can be manipulated in memory, but will not be seen in Rhino or saved. A Point3d is added to the Rhino document through the
rs.AddPoint() command. To create a Point3d from a Guid, use the
rs.PointCoordinates(guid) or the