Creating a 2D Circular Mesh in Unity

Question

I currently have a "CreateMesh" script that can be put as a component of an object with a Mesh Renderer, and a Mesh Filter, and a 2D mesh is created with a polygon collider in the dimensions of the mesh given a "MeshType" variable is set to either "tri" or "box" (for a triangle and rectangle mesh respectively.) I want to also add the ability to create a circular mesh however from some research I've realised this isn't as simple as I first thought. However I'm yet to find anything that's helping.

This is the code I have for the box and triangle meshes:

public float width = 5f;
public float height = 5f;

public string meshType;

public PolygonCollider2D polyCollider;

void Start()
{
    polyCollider = GetComponent<PolygonCollider2D>();
}

// Update is called once per frame
void Update () {
    if (meshType == "tri")
    {
        TriangleMesh(width, height);
    }
    if (meshType == "box")
    {
        BoxMesh(width, height);
    }

}

void TriangleMesh(float width, float height)
{
    MeshFilter mf = GetComponent<MeshFilter>();
    Mesh mesh = new Mesh();
    mf.mesh = mesh;

    //Verticies
    Vector3[] verticies = new Vector3[3]
    {
        new Vector3(0,0,0), new Vector3(width, 0, 0), new Vector3(0, height, 0)
    };

    //Triangles
    int[] tri = new int[3];

    tri[0] = 0;
    tri[1] = 2;
    tri[2] = 1;

    //normals
    Vector3[] normals = new Vector3[3];

    normals[0] = -Vector3.forward;
    normals[1] = -Vector3.forward;
    normals[2] = -Vector3.forward;

    //UVs
    Vector2[] uv = new Vector2[3];

    uv[0] = new Vector2(0, 0);
    uv[0] = new Vector2(1, 0);
    uv[0] = new Vector2(0, 1);

    //initialise
    mesh.vertices = verticies;
    mesh.triangles = tri;
    mesh.normals = normals;
    mesh.uv = uv;

    //setting up collider
    polyCollider.pathCount = 1;

    Vector2[] path = new Vector2[3]
    {
        new Vector2(0,0), new Vector2(0, height), new Vector2(width, 0)
    };

    polyCollider.SetPath(0, path);

}

void BoxMesh(float width, float height)
{
    MeshFilter mf = GetComponent<MeshFilter>();
    Mesh mesh = new Mesh();
    mf.mesh = mesh;

    //Verticies
    Vector3[] verticies = new Vector3[4]
    {
        new Vector3(0,0,0), new Vector3(0, height, 0), new Vector3(width, height, 0), new Vector3(width, 0, 0)
    };

    //Triangles
    int[] tri = new int[6];

    tri[0] = 0;
    tri[1] = 1;
    tri[2] = 3;

    tri[3] = 1;
    tri[4] = 2;
    tri[5] = 3;

    //normals
    Vector3[] normals = new Vector3[4];

    normals[0] = -Vector3.forward;
    normals[1] = -Vector3.forward;
    normals[2] = -Vector3.forward;
    normals[3] = -Vector3.forward;

    //UVs
    Vector2[] uv = new Vector2[4];

    uv[0] = new Vector2(0, 0);
    uv[1] = new Vector2(0, 1);
    uv[2] = new Vector2(1, 1);
    uv[3] = new Vector2(1, 0);

    //initialise
    mesh.vertices = verticies;
    mesh.triangles = tri;
    mesh.normals = normals;
    mesh.uv = uv;

    //setting up collider
    polyCollider.pathCount = 1;

    Vector2[] path = new Vector2[4]
    {
        new Vector2(0,0), new Vector2(0, height), new Vector2(width, height), new Vector2(width, 0)
    };

    polyCollider.SetPath(0, path);

}

So essentially I want a function that I could call in the update method that would simply create a circular mesh. E.g:

void Update () {
   if (meshType == "tri")
   {
       TriangleMesh(width, height);
   }
   if (meshType == "box")
   {
       BoxMesh(width, height);
   }
   if (meshType == "circle")
   {
       CircleMesh(radius);
   }
}

Answer 1

I have less than 50 reputation and so I can't just comment on @Tom Ryan's answer.

With that said, beware that his solution doesn't include the UVs for the mesh. Here is that addition:

//uvs
Vector2[] uvs = new Vector2[vertices.Length];
for (int i = 0; i < uvs.Length; i++)
{
    uvs[i] = new Vector2(vertices[i].x / (radius*2) + 0.5f, vertices[i].y / (radius*2) + 0.5f);
}

// Later...
mesh.uv = uvs;