UIMeshRenderer.cs

//Custom UI Meshes script by @MinionsArt
using UnityEngine;
using UnityEngine.UI;
[ExecuteAlways]
[RequireComponent(typeof(CanvasRenderer))]
public class UIMeshRenderer : MaskableGraphic
{
    [SerializeField]
    Mesh mesh;
    [SerializeField]
    bool preserveAspect;

    protected override void OnEnable()
    {
        base.OnEnable();
        SetVerticesDirty();
        SetMaterialDirty();
    }

    protected override void OnRectTransformDimensionsChange()
    {
        base.OnRectTransformDimensionsChange();
        SetVerticesDirty();
        SetMaterialDirty();
    }

    protected override void OnPopulateMesh(VertexHelper vh)
    {
        vh.Clear();
        if (mesh == null) return;

        Rect rect = rectTransform.rect;

        // handle preserving aspect
        if (preserveAspect && mesh.bounds.extents.sqrMagnitude > 0f)
        {
            float meshRatio = mesh.bounds.extents.x / mesh.bounds.extents.y;
            float rectRatio = rect.width / rect.height;

            if (meshRatio > rectRatio)
            {
                float oldHeight = rect.height;
                rect.height = rect.width / meshRatio;
                rect.y += (oldHeight - rect.height) * rectTransform.pivot.y;
            }
            else
            {
                float oldWidth = rect.width;
                rect.width = rect.height * meshRatio;
                rect.x += (oldWidth - rect.width) * rectTransform.pivot.x;
            }
        }
        // scale to rect transform size
        float scaleX = rect.width / mesh.bounds.size.x;
        float scaleY = rect.height / mesh.bounds.size.y;
        // mesh center in case of offcenter pivot
        Vector3 center = mesh.bounds.center;

        Vector3[] verts = mesh.vertices;
        Vector2[] uvs = mesh.uv;
        // check if we have vertex colors assigned
        Color32[] colors = mesh.colors32.Length == verts.Length ? mesh.colors32 : null;



        for (int i = 0; i < verts.Length; i++)
        {
            // use scale on all vertices and offset
            Vector3 vert = verts[i] - center;
            vert.x *= scaleX;
            vert.y *= scaleY;
            vert.z *= scaleX;

            // use color assigned in graphic if theres no vertex color
            Color32 col = colors != null ? colors[i] : (Color32)this.color;
            // set new vertices
            vh.AddVert(vert, col, uvs[i]);
        }
        // set triangles
        int[] tris = mesh.triangles;
        for (int i = 0; i < tris.Length; i += 3)
            vh.AddTriangle(tris[i], tris[i + 1], tris[i + 2]);
    }

#if UNITY_EDITOR
    protected override void OnValidate()
    {
        base.OnValidate();
        SetVerticesDirty();
        SetMaterialDirty();

    }
#endif
}