Why my Triangles starts overlapping when terrainSize too high?

Question

I have a weird problem. At the moment I am doing a selfmade Terrain generator, for now I am doing a "plane" generation only for the bottom area with flat surface. My problem is that when I set terrainSize too high the triangles starts overlapping ironically.

Here is a picture when i set terrainSize to 120:

Here is a picture when i set the terrainSize to 200:

At the size 200 looks like its overlapping twice, i found out that the max terrainSize for me is 114 at 115 it starts overlapping.

Here is my code, maybe you can find something out and help me and other on this platform:

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

[RequireComponent(typeof(MeshFilter))]
public class MeshGeneratorSecond : MonoBehaviour
{
    [SerializeField] private int terrainSize;

    private Mesh myMesh;
    private Vector3[] vertices;
    private int[] triangles;

    private int verticesInVertex = 5;
    private int trianglesInVertex = 4;


    void Start()
    {
        myMesh = new Mesh();
        GetComponent<MeshFilter>().mesh = myMesh;

        vertices = new Vector3[terrainSize * terrainSize * 5];
        triangles = new int[terrainSize * terrainSize * 12];

        StartCoroutine(CreateShape());
    }

    IEnumerator CreateShape()
    {
        int vertex = 0;
        int triangle = 0;
        for(int x = 0; x < terrainSize; x++)
        {
            for(int z = 0; z < terrainSize; z++)
            {
                vertices[vertex] = new Vector3(x, 0, z);
                vertices[vertex + 1] = new Vector3(x, 0, z + 1);
                vertices[vertex + 2] = new Vector3(x + 1, 0, z + 1);
                vertices[vertex + 3] = new Vector3(x + 1, 0, z);
                vertices[vertex + 4] = new Vector3(x + 0.5f, 0, z + 0.5f);

                //First Triangle
                triangles[triangle] = vertex;
                triangles[triangle + 1] = vertex + 1;
                triangles[triangle + 2] = vertex + 4;

                //Second Triangle
                triangles[triangle + 3] = vertex + 1;
                triangles[triangle + 4] = vertex + 2;
                triangles[triangle + 5] = vertex + 4;

                //Third Triangle
                triangles[triangle + 6] = vertex + 2;
                triangles[triangle + 7] = vertex + 3;
                triangles[triangle + 8] = vertex + 4;

                //Fourth Triangle
                triangles[triangle + 9] = vertex + 3;
                triangles[triangle + 10] = vertex;
                triangles[triangle + 11] = vertex + 4;

                vertex += verticesInVertex;
                triangle += trianglesInVertex * 3;
            }
            UpdateMesh();
            yield return new WaitForSeconds(.1f);
        }
    }

    private void UpdateMesh()
    {
        myMesh.Clear();

        myMesh.vertices = vertices;
        myMesh.triangles = triangles;

        myMesh.RecalculateNormals();
    }
    public void OnDrawGizmos()
    {
        Gizmos.color = Color.red;
        for(int i = 0; i < vertices.Length; i++)
        {
            Gizmos.DrawSphere(vertices[i], .1f);
        }
    }

}

In this Question here i called it area size but in my Code its the **terrainSize** variable. — Maximilian Grinik, Jan 27 '22 at 21:48
Unity has a maximum vertex limit of 65535 per mesh, and due to your vertex algorithm, when you try to do your `terrainSize=115` mesh, you attempt to use 115x115x5 = 66125 vertices, which is over the limit. — Ruzihm, Jan 27 '22 at 23:07
Does this answer your question? [How to use meshes with more than 64k vertices in Unity 2018.1](https://stackoverflow.com/q/50433894/1092820) — Ruzihm, Jan 27 '22 at 23:07
You may also want to look into how to re-use vertices instead of creating up to 4 vertices that all have the same position thousands of times. — Ruzihm, Jan 27 '22 at 23:09

score 0 · Answer 1 · answered Jan 29 '22 at 13:35

Mesh buffers are 16 bit by default. See Mesh-indexFormat:

Index buffer can either be 16 bit (supports up to 65535 vertices in a mesh), or 32 bit (supports up to 4 billion vertices). Default index format is 16 bit, since that takes less memory and bandwidth.

Note! Ehen you want to change the 16-bit buffer to 32-bit buffer, you can change with this line of code:

mesh.indexFormat = UnityEngine.Rendering.IndexFormat.UInt32;

Why my Triangles starts overlapping when terrainSize too high?

1 Answers1