Generating stream lines from vectorfield

Grasshopper Developer
1

Hi everyone,

I’m trying to create streamlines from seed points in Grasshopper using GhPython, but I’m getting unexpected Guid errors when working with data from Deconstruct Plane. I have points and vectors and I need to create streamlines from there.

:light_bulb: Context:

  • I have a Topos simulation that outputs planes.
  • I’m using Deconstruct Plane to extract:
    • Origin → input as pts (Point3d)
    • Z → input as vecs (Vector3d)
  • I transfer these using Data Output/Input to a GhPython script that generates streamlines from seed points (seed_pts).

:warning: Problem:

In the GhPython component, I get errors like:

  • 'Guid' object is not iterable
  • 'Guid' object has no len()
  • 'Guid' object is not subscriptable

Despite flattening all inputs, they seem to arrive as Guid instead of Point3d or Vector3d, causing the script to fail.

:white_check_mark: What I’ve tried:

  • Flattening all inputs
  • Checking types using type() and isinstance()
  • Attempted to manually convert inputs (e.g., accessing coordinates)
  • Basic data validation in the script

:red_question_mark: Question:

How can I ensure that data passed from Deconstruct Plane through Data Output/Input into GhPython is received as proper Point3d and Vector3d objects? Is there a better method to pass geometry from Grasshopper to GhPython when working with vector fields?

Thanks in advance for any help or pointers!
Vectors.gh (127.2 KB)

2

Sounds like you need to set appropriate access types (i.e. right click input parameters and select Item, List or Tree Access and relevant type hints (i.e. right click input parameters and set Type Hint to Point3d or Vector3d).