Is unity limiting the number or vertices per mesh?

Question

I am generating island made of cubes in unity. For each cell in a grid, I draw a cube made of vertices and add it to a mesh.

Here is a sample of my code :

void DrawTerrainMesh(Cell[,,] grid){
        Mesh mesh = new(); 
        List<Vector3> vertices  = new List<Vector3>(); 
        List<int> triangles = new List<int>(); 
        
        for (int z = 0; z < z_size; z++) {
            for (int y = 0; y < size; y++) {
                for (int x = 0; x < size; x++) {
                    Cell cell = grid[x, y, z];
                    if (cell == null)
                        continue;
                    if (cell.cellType == Cell.CellType.Earth) {
                        // Calculate the positions of the 8 vertices
                        Vector3[] cubeVertices = new Vector3[8];
                        for (int i = 0; i < 2; i++) {
                            float xv = i == 0 ? 0.5f : -0.5f;
                            for (int j = 0; j < 2; j++) {
                                float yv = j == 0 ? 0.5f : -0.5f;
                                for (int k = 0; k < 2; k++) {
                                    float zv = k == 0 ? 0.5f : -0.5f;
                                    Vector3 vertex = new Vector3(xv + x - size/2, zv + z,yv + y - size/2);
                                    cubeVertices[i * 4 + j * 2 + k] = vertex;
                                }
                            }
                        }
                
                        AddTriangles(vertices, triangles, cubeVertices[0], cubeVertices[2], cubeVertices[4], cubeVertices[6]); // Top
                        AddTriangles(vertices, triangles, cubeVertices[0], cubeVertices[1], cubeVertices[2], cubeVertices[3]); // left 
                        AddTriangles(vertices, triangles, cubeVertices[2], cubeVertices[3], cubeVertices[6], cubeVertices[7]); // back  
                        AddTriangles(vertices, triangles, cubeVertices[3], cubeVertices[1], cubeVertices[7], cubeVertices[5]); // Bottom
                        AddTriangles(vertices, triangles, cubeVertices[4], cubeVertices[6], cubeVertices[5], cubeVertices[7]); // right
                        AddTriangles(vertices, triangles, cubeVertices[0], cubeVertices[4], cubeVertices[1], cubeVertices[5]); // front */
                    }
                }
            }
        }

        

        
        
        mesh.vertices = vertices.ToArray(); 
        mesh.triangles = triangles.ToArray(); 
        mesh.RecalculateNormals(); 
        print(mesh.vertices.Length);
        MeshFilter meshFilter = gameObject.AddComponent<MeshFilter>(); 
        meshFilter.mesh = mesh; 

        MeshRenderer meshRenderer = gameObject.AddComponent<MeshRenderer>(); 

    }

The problem is that it only draw the first two layers of my island (which are supposed to be made more than 2 layers).

Here is an example :

So it was supposed to draw my whole island but instead it draws only the first two layers.

I know the problem doesn't come from my code itself (I mean not that I can see), because if i only draw the top face of my cubes, it draws every layers of the island :

AddTriangles(vertices, triangles, cubeVertices[0], cubeVertices[2], cubeVertices[4], cubeVertices[6]); // Top
                        //AddTriangles(vertices, triangles, cubeVertices[0], cubeVertices[1], cubeVertices[2], cubeVertices[3]); // left 
                        //AddTriangles(vertices, triangles, cubeVertices[2], cubeVertices[3], cubeVertices[6], cubeVertices[7]); // back  
                        //AddTriangles(vertices, triangles, cubeVertices[3], cubeVertices[1], cubeVertices[7], cubeVertices[5]); // Bottom
                        //AddTriangles(vertices, triangles, cubeVertices[4], cubeVertices[6], cubeVertices[5], cubeVertices[7]); // right
                        //AddTriangles(vertices, triangles, cubeVertices[0], cubeVertices[4], cubeVertices[1], cubeVertices[5]); // front */

Here you can see the top of the moutains of the island.

So my guess is that unity limits the number of vertices a mesh can have. Is it true? How to deal with this?

Any idea?

Answer 1

This will depend on the mesh index format. By default, it will use uint16 indexing which is a maximum if 65536 vertices. Index format can also be made to use uint32, which bumps this number up to 4 billion. For more information, see the documentation about Mesh.indexFormat