Process IronPython.Runtime.List in C#

Grasshopper
1

Hi so I’m working on a custom Grasshopper plugin. I’m running into an issue where, when I try to use the “Rhino.NodeInCode” to call the “Mesh Shadow” component, it will return a “ironpython.runtime.list” rather than some usable object type. It won’t let me cast it to a “Curve”.

I’ve tried just using a regular “Object” class to store it but that doesn’t come into Grasshopper nicely. It doesn’t show up as curves but as just a “ironpython.runtime.list”. It does seem to return a curve if I plug similar code into a C# node and run it as a one-off.

Does anyone have a suggestion on how to deal with this properly? Or where to look to learn more about this problem? Thank you.

using Rhino.NodeInCode;

private SunPosition currentSunPosition;
private Mesh originObject;

public readonly Curve ShadowCurve;

private ComponentFunctionInfo ghMeshShadow = Components.FindComponent("MeshShadow");

private Curve CreateShadowCurve()
        {
            string[] warnings;
            Plane planeXY = new Plane(new Point3d(0.0, 0.0, 0.0), new Vector3d(0.0, 0.0, 1.0));

            object[] result = ghMeshShadow.Evaluate(new Object[] {
                 originObject, 
                 currentSunPosition.SunVector, 
                 planeXY }, false, out warnings);

            return (Curve) result[0];
        }
2

Hi @c.woodward10,

In terms of passing an IronPython list object to C#, let me google that for you… here’s a possible solution.

Since you seem proficient in programming, another way would be to come up with your very own mesh shadow code. This is probably not hard at all.

3

(Can’t tell if this response was meant to be snarky or not…)
I did get it to work from that link so thank. Using the right Google search query definitely is helpful since when I google’d around, I didn’t find that particular topic.

Also trying to avoid making my own version of Mesh Shadow since GH’s works just fine. (and I’m essentially learning C# while making this plugin)

Anyways, here’s what worked for those curious:

object[] result = ghMeshShadow.Evaluate(new Object[] { originObject, currentSunPosition.SunVector, 
                          planeXY }, false, out warnings);    
IList<object> resultList = (IList<object>)result[0];
return (Curve)resultList[0];
2 Likes
4

This is correct. To improve this, just make sure that your lookup is not out of range. You should probably do this in a couple of lines (check that IList will work, using C# keywords as, is, or some other one, then check if there is an item [0], by checking Count.

As you noticed, there is no need to know that the returned list is Ironpython.Runtime.List. You can expect lists to be IList, or IList<object>.

1 Like
5

Awesome, thank you. That’s quite helpful.