the code is based on Unity3d 4.6.x, the api may changed.

CircleText.cs

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
using System.Collections.Generic;

public class CircleText : BaseVertexEffect
{
	
	public int radius = 50;
	public float spaceCoff = 1f;

	#region implemented abstract members of BaseVertexEffect
	public override void ModifyVertices (List<UIVertex> verts)
	{
		if (!IsActive ())
			return;

		if (radius == 0) {
			Debug.LogWarning ("radius could not be zero!");
			return;
		}

		Text text = GetComponent<Text> ();
		TextGenerator tg = text.cachedTextGenerator;

		float perimeter = Mathf.PI * radius * 2;
		float weight = text.fontSize / perimeter * spaceCoff;
		float radStep = Mathf.PI * 2 * weight;
		float charOffset = tg.characterCountVisible / 2f - 0.5f;

		for (int i = 0; i < tg.characterCountVisible; i++) {
			var lb = verts [i * 4];
			var lt = verts [i * 4 + 1];
			var rt = verts [i * 4 + 2];
			var rb = verts [i * 4 + 3];

			Vector3 center = Vector3.Lerp (lb.position, rt.position, 0.5f);
			Matrix4x4 move = Matrix4x4.TRS (center * -1, Quaternion.identity, Vector3.one);

			float rad = Mathf.PI / 2 + (charOffset - i) * radStep;
			Vector3 pos = new Vector3 (Mathf.Cos (rad), Mathf.Sin (rad), 0) * radius;

			Quaternion rotation = Quaternion.Euler (0, 0, rad * 180 / Mathf.PI - 90);
			Matrix4x4 rotate = Matrix4x4.TRS (Vector3.zero, rotation, Vector3.one);
			Matrix4x4 place = Matrix4x4.TRS (pos, Quaternion.identity, Vector3.one);
			Matrix4x4 transform = place * rotate * move;

			lb.position = transform.MultiplyPoint (lb.position);
			lt.position = transform.MultiplyPoint (lt.position);
			rt.position = transform.MultiplyPoint (rt.position);
			rb.position = transform.MultiplyPoint (rb.position);

			verts [i * 4] = lb;
			verts [i * 4 + 1] = lt;
			verts [i * 4 + 2] = rt;
			verts [i * 4 + 3] = rb;
		}
	}
	#endregion

}

大佬能更新一下吗

测试于 unity 2018.1.8f1
`
public class CircleText : BaseMeshEffect
{

public int radius = 50;
public float spaceCoff = 1f;

List<UIVertex> verts;


#region implemented abstract members of BaseMeshEffect
public override void ModifyMesh(VertexHelper vh)
{
    if (!IsActive())
        return;

    if (radius == 0)
    {
        Debug.LogWarning("radius could not be zero!");
        return;
    }
    if (verts == null)
        verts = new List<UIVertex>();
    else
        verts.Clear();

    Text text = GetComponent<Text>();
    TextGenerator tg = text.cachedTextGenerator;

    float perimeter = Mathf.PI * radius * 2;
    float weight = text.fontSize / perimeter * spaceCoff;
    float radStep = Mathf.PI * 2 * weight;
    float charOffset = tg.characterCountVisible / 2f - 0.5f;

    var count = vh.currentVertCount;
    if (count == 0)
        return;
    Debug.Log("count:" + count);
    for (int i = 0; i < count; i++)
    {
        var vertex = new UIVertex();
        vh.PopulateUIVertex(ref vertex, i);
        verts.Add(vertex);
    }

    for (int i = 0; i < tg.characterCountVisible; i++)
    {
        var lb = verts[i * 4];
        var lt = verts[i * 4 + 1];
        var rt = verts[i * 4 + 2];
        var rb = verts[i * 4 + 3];

        Vector3 center = Vector3.Lerp(lb.position, rt.position, 0.5f);
        Matrix4x4 move = Matrix4x4.TRS(center * -1, Quaternion.identity, Vector3.one);

        float rad = Mathf.PI / 2 + (charOffset - i) * radStep;
        Vector3 pos = new Vector3(Mathf.Cos(rad), Mathf.Sin(rad), 0) * radius;

        Quaternion rotation = Quaternion.Euler(0, 0, rad * 180 / Mathf.PI - 90);
        Matrix4x4 rotate = Matrix4x4.TRS(Vector3.zero, rotation, Vector3.one);
        Matrix4x4 place = Matrix4x4.TRS(pos, Quaternion.identity, Vector3.one);
        Matrix4x4 transform = place * rotate * move;

        lb.position = transform.MultiplyPoint(lb.position);
        lt.position = transform.MultiplyPoint(lt.position);
        rt.position = transform.MultiplyPoint(rt.position);
        rb.position = transform.MultiplyPoint(rb.position);

        vh.SetUIVertex(lb, i * 4);
        vh.SetUIVertex(lt, i * 4 + 1);
        vh.SetUIVertex(rt, i * 4 + 2);
        vh.SetUIVertex(rb, i * 4 + 3);
    }
}

#endregion

}
`

ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index System.ThrowHelper.ThrowArgumentOutOfRangeException (System.ExceptionArgument argument, System.ExceptionResource resource) (at <437ba245d8404784b9fbab9b439ac908>:0) System.ThrowHelper.ThrowArgumentOutOfRangeException () (at <437ba245d8404784b9fbab9b439ac908>:0) System.Collections.Generic.List1[T].get_Item (System.Int32 index) (at <437ba245d8404784b9fbab9b439ac908>:0)
CircleText.ModifyMesh (UnityEngine.UI.VertexHelper vh) (at Assets/Scripts/CircleText.cs:51)
UnityEngine.UI.Graphic.DoMeshGeneration () (at /Applications/Unity/Hub/Editor/2019.4.0f1/Unity.app/Contents/Resources/PackageManager/BuiltInPackages/com.unity.ugui/Runtime/UI/Core/Graphic.cs:629)
UnityEngine.UI.Graphic.UpdateGeometry () (at /Applications/Unity/Hub/Editor/2019.4.0f1/Unity.app/Contents/Resources/PackageManager/BuiltInPackages/com.unity.ugui/Runtime/UI/Core/Graphic.cs:614)
UnityEngine.UI.Text.UpdateGeometry () (at /Applications/Unity/Hub/Editor/2019.4.0f1/Unity.app/Contents/Resources/PackageManager/BuiltInPackages/com.unity.ugui/Runtime/UI/Core/Text.cs:569)
UnityEngine.UI.Graphic.Rebuild (UnityEngine.UI.CanvasUpdate update) (at /Applications/Unity/Hub/Editor/2019.4.0f1/Unity.app/Contents/Resources/PackageManager/BuiltInPackages/com.unity.ugui/Runtime/UI/Core/Graphic.cs:572)
UnityEngine.UI.CanvasUpdateRegistry.PerformUpdate () (at /Applications/Unity/Hub/Editor/2019.4.0f1/Unity.app/Contents/Resources/PackageManager/BuiltInPackages/com.unity.ugui/Runtime/UI/Core/CanvasUpdateRegistry.cs:210)
UnityEngine.Canvas:SendWillRenderCanvases() (at /Users/builduser/buildslave/unity/build/Modules/UI/ScriptBindings/UICanvas.bindings.cs:72)`

一添加就报错