How to generate objects from a script in the editor, i.e. before runtime?

Questions & Answers
1

I’m making a “rope” object, which is comprised of a series of links and hinges. The formation is like this:

Link
Hinge
Link

Links are just capsules with a Rigidbody, and Hinges are capsules that have two Hinge Joints, one linked to the link above it, one connected to the link below.

The result is a physics-based rope (more of a chain, to be honest) that swings at each Hinge as you’d expect.

Here’s a screenshot of the Rope to help visualize:

171060-screen-shot-2020-11-15-at-43310-pm.png
171060-screen-shot-2020-11-15-at-43310-pm.png2880×770 217 KB

Obviously it’s tedious to manually add Links and Hinges to increase the length of the rope. So, what I want to be able to do is edit the parameters of this rope in the inspector and have its script add Links and Hinges automatically.

My understanding is that I can run some script in editor to achieve this.

I currently have a script called “Rope” on an empty GameObject, with the expectation of generating the Rope Components (Links and Hinges) as children.

Here’s the Rope script as it stands…

[ExecuteInEditMode]
public class Rope : MonoBehaviour
{
    GameObject[] components = Resources.LoadAll<GameObject>("RopeComponents");

    [SerializeField] int ropeLength;
    [SerializeField] int numberOfLinks;

    public void CreateNewSection(Vector3 pos)
    {
        var newHinge = Instantiate(components[0],gameObject.transform);
        var newLink = Instantiate(components[1], gameObject.transform);

        MoveComps(newHinge, newLink, pos);

        var hinges = newHinge.GetComponents<HingeJoint>();
        hinges[1].connectedBody = newLink.GetComponent<Rigidbody>();
    }

    void MoveComps(GameObject hinge, GameObject link, Vector3 pos)
    {
        hinge.transform.position = pos;
        link.transform.position = pos + Vector3.down;
    }
}

I also have an EditorScript to make a button so that I can run the CreateNewSection method from the Rope script: (Warning: it’s totally in shambles, as this is the part of the process I really don’t understand…)

using UnityEditor;

[CustomEditor(typeof(Rope))]
public class RopeEditor : Editor
{
    SerializedObject ropeObj;

    public override void OnInspectorGUI()
    {
        rope = serializedObject;
        DrawDefaultInspector();
        DrawRopeEditor();
    }

    void DrawRopeEditor()
    {
        GUILayout.Space(5);
        GUILayout.Label("Rope Editor", EditorStyles.boldLabel);

        DrawCommitButton();
    }

    void DrawCommitButton()
    {
        if (GUILayout.Button(text: "Commit"))
        {
            rope.CreateNewSection(Vector3.zero);
        }

    }
}

Anyone have experience writing Editor Scripts and procedurally building objects like this?

The problem with the current way I’m attempting this is that I don’t know how to reference my Rope script from my editor script so that I can call the CreateNewSection() method.

Thanks for reading, and let me know if you have any thoughts!

2

You can initialize your rope in Start() or Awake() where you can read the rope length and number of links which have been adjusted from the inspector. I don’t think you need to mess with the editor itself.

Try this tutorial:

But if you really need to deal with the editor, try this: