Why is my submesh not rendering properly

Unity Engine
,
1

i have 2 meshes that ive tried to turn into a 2 submeshes but it just sort of combines them when i do it, does anyone know why?

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.Linq;

public class plane : MonoBehaviour
{
    public GameObject obmesh1;
    public GameObject obmesh2;
    public int[] triangles1;
    public int[] triangles2;
    public Vector3[] verticies1;
    public Vector3[] verticies2;
    public Vector3[] allverticies;
    public Vector2[] uvs1;
    public Vector2[] uvs2;
    public Vector2[] alluvs;


    // Start is called before the first frame update
    void Start()
    {
       
        Mesh mesh1 = obmesh1.GetComponent<MeshFilter>().mesh;
        Mesh mesh2 = obmesh2.GetComponent<MeshFilter>().mesh;
        Mesh mesh = GetComponent<MeshFilter>().mesh;
        //mesh.Clear();
        mesh.subMeshCount = 2;
        Debug.Log("Submeshes: " + mesh.subMeshCount);
       
        int[] triangles1 = mesh1.GetTriangles(0);
        int[] triangles2 = mesh2.GetTriangles(0);
        verticies1 = mesh1.vertices;
        verticies2 = mesh2.vertices;
       
        allverticies = verticies1.Concat(verticies2).ToArray();

        uvs1 = mesh1.uv;
        uvs2 = mesh2.uv;
        alluvs = uvs1.Concat(uvs2).ToArray();
        mesh.uv = alluvs;
       
        mesh.vertices = allverticies;
       
        mesh.SetTriangles(triangles1, 0);
        mesh.SetTriangles(triangles2, 1);
        mesh.RecalculateBounds();
        mesh.RecalculateNormals();
      
    }

}

8376903--1104369--mesh.png

2

You have not adjusted the indices of your second submesh. Keep in mind that the triangles consist of indices into the vertices array. Since you concat your vertices into a single array, the vertices of the second mesh would be offset.

Just as the most simple example. Assume you have two meshes and each mesh only has 3 vertices and a single triangle. So for the first mesh you would have the vertices va0, va1, va2 and a triangles array that looks like [0, 1, 2]. The second mesh would look pretty much the same but has the vertices vb0, vb1, vb2.

After combining them you have a single vertex array with 6 elements that looks like this va0, va1, va2, vb0, vb1, vb2. The two triangle arrays however need to be adjusted to: [0, 1, 2] for the first submesh and [3, 4, 5] for the second one since the vertices for the second submesh start at index 3, after the first one.

3

ive tried to do this to off set it, but it gives error:
Failed setting triangles. Some indices are referencing out of bounds vertices. IndexCount: 600, VertexCount: 145
UnityEngine.Mesh:SetTriangles (int[ ],int)

for (int i = 0; i < triangles2.Length; i++)
        {
            triangles2[i] = triangles2[i] + triangles1.Length;
        }
4

This makes no sense :slight_smile: The indices refer to the vertices array. So adding the length of the triangles array makes no sense. You should add the length of the vertices array instead.

5

Thankyou it all works now :slight_smile: