CombineMeshes with Different Materials

Questions & Answers
1

Hi,

I need to use CombineMeshes() but there is something unclear about how it works.

My situation is this: I need to combine multiple meshes of different materials into one mesh, with (I’m assuming) one submesh per unique material. Sometimes there may be multiple instances of the same mesh using a different material, or multiple instances of the same mesh using the same material but for different submeshes.

The confusion is, the Mesh object doesn’t contain information about which materials are being used for a particular instance, and CombineMesh doesn’t request that information from a MeshRenderer object, which is the only thing that DOES contain that information. Two different meshes may have multiple submeshes, say 2 submeshes, but mesh1’s submesh1’s material might not be the same as mesh2’s submesh1’s material. How would it know to put them into different submeshes?

I read that you can specify that through CombineInstance.subMeshIndex:

ArrayList materials = new ArrayList();
ArrayList combineInstances = new ArrayList();
MeshFilter[] meshFilters = <Object>.GetComponentsInChildren<MeshFilter>();

foreach( MeshFilter meshFilter in meshFilters )
{
    MeshRenderer meshRenderer = meshFilter.GetComponent<MeshRenderer>();

    for(int s = 0; s < meshFilter.sharedMesh.subMeshCount; s++)
    {
        // !! Assumes that submesh index will always correspond to material index !!
        int materialArrayIndex;

        for(materialArrayIndex = 0; materialArrayIndex < materials.Count; materialArrayIndex++)
        {
            if(materials[materialArrayIndex] == meshRenderer.materials~~)~~

break;
}

if(materialArrayIndex == materials.Count)
materials.Add(meshRenderer.materials~~);
CombineInstance combineInstance;
combineInstance.transform = meshRenderer.transform;
// ---------------------------------------------------------------
combineInstance.subMeshIndex = materialArrayIndex;
combineInstance.mesh = meshFilter.sharedMesh ??? .submesh ???
// ---------------------------------------------------------------
combineInstances.Add( combineInstance );
}
}~~
But as you can see, meshFilter.sharedMesh doesn’t give you access to the individual submeshes. So how is it supposed to know how to separate them?
Thanks for helping.

7

I’ve combined the Unity3d example, Zergling103, and added Benjamen247 modifications, to create a script which will combine sub meshes with different materials dynamically at runtime:

using UnityEngine;
using System.Collections;

public class MeshCombiner : MonoBehaviour
{
    public void Awake()
    {
        ArrayList materials = new ArrayList();
        ArrayList combineInstanceArrays = new ArrayList();
        MeshFilter[] meshFilters = gameObject.GetComponentsInChildren<MeshFilter>();

        foreach (MeshFilter meshFilter in meshFilters)
        {
            MeshRenderer meshRenderer = meshFilter.GetComponent<MeshRenderer>();

            if (!meshRenderer ||
                !meshFilter.sharedMesh ||
                meshRenderer.sharedMaterials.Length != meshFilter.sharedMesh.subMeshCount)
            {
                continue;
            }

            for (int s = 0; s < meshFilter.sharedMesh.subMeshCount; s++)
            {
                int materialArrayIndex = Contains(materials, meshRenderer.sharedMaterials~~.name);~~

if (materialArrayIndex == -1)
{
materials.Add(meshRenderer.sharedMaterials~~);
materialArrayIndex = materials.Count - 1;
}~~
combineInstanceArrays.Add(new ArrayList());

CombineInstance combineInstance = new CombineInstance();
combineInstance.transform = meshRenderer.transform.localToWorldMatrix;
combineInstance.subMeshIndex = s;
combineInstance.mesh = meshFilter.sharedMesh;
(combineInstanceArrays[materialArrayIndex] as ArrayList).Add(combineInstance);
}
}

// Get / Create mesh filter & renderer
MeshFilter meshFilterCombine = gameObject.GetComponent();
if (meshFilterCombine == null)
{
meshFilterCombine = gameObject.AddComponent();
}
MeshRenderer meshRendererCombine = gameObject.GetComponent();
if (meshRendererCombine == null)
{
meshRendererCombine = gameObject.AddComponent();
}

// Combine by material index into per-material meshes
// also, Create CombineInstance array for next step
Mesh[] meshes = new Mesh[materials.Count];
CombineInstance[] combineInstances = new CombineInstance[materials.Count];

for (int m = 0; m < materials.Count; m++)
{
CombineInstance[] combineInstanceArray = (combineInstanceArrays[m] as ArrayList).ToArray(typeof(CombineInstance)) as CombineInstance[];
meshes[m] = new Mesh();
meshes[m].CombineMeshes(combineInstanceArray, true, true);

combineInstances[m] = new CombineInstance();
combineInstances[m].mesh = meshes[m];
combineInstances[m].subMeshIndex = 0;
}

// Combine into one
meshFilterCombine.sharedMesh = new Mesh();
meshFilterCombine.sharedMesh.CombineMeshes(combineInstances, false, false);

// Destroy other meshes
foreach (Mesh oldMesh in meshes)
{
oldMesh.Clear();
DestroyImmediate(oldMesh);
}

// Assign materials
Material[] materialsArray = materials.ToArray(typeof(Material)) as Material[];
meshRendererCombine.materials = materialsArray;

foreach (MeshFilter meshFilter in meshFilters)
{
DestroyImmediate(meshFilter.gameObject);
}
}

private int Contains(ArrayList searchList, string searchName)
{
for (int i = 0; i < searchList.Count; i++)
{
if (((Material)searchList*).name == searchName)*
{
return i;
}
}
return -1;
}
}
It works great for my needs (dungeon generator).

2

Mesh.CombineMeshes (or to be more precise the Mesh itself) can only use one material per submesh. The submesh index is the same as the material index. If you have more materials then submeshes Unity will apply those to one of the submeshes (can’t remember which one, the first or the last, i guess to the last one).

Why do you need to combine them? Two or more different material means two or more drawcalls. So you don’t have much benefit from combining the meshes except they come up as one.

If you combine meshes you usually use a texture atlas so you need only one material.

5

I used Zergling103’s script (thanks by the way!) but I was having problems with the position of the generated mesh not being in the same location. This seemed to be only the case when the object was not at world coordinates (0,0,0).

I also removed the Objects variable and changed it so the script will just combine all meshes and materials on the object that is attached to.

You will need to manually call Combine() to execute it, or right-click the script in the inspector and choose Combine from the menu.

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

public class CombineMeshes : MonoBehaviour
{
[ContextMenu(“Combine”)]
public void Combine ()
{
// Find all mesh filter submeshes and separate them by their cooresponding materials
ArrayList materials = new ArrayList ();
ArrayList combineInstanceArrays = new ArrayList ();
Matrix4x4 myTransform = transform.worldToLocalMatrix;

    MeshFilter[] meshFilters = this.gameObject.GetComponentsInChildren<MeshFilter> ();

    foreach (MeshFilter meshFilter in meshFilters) {
        MeshRenderer meshRenderer = meshFilter.GetComponent<MeshRenderer> ();

        // Handle bad input
        if (!meshRenderer) { 
            Debug.LogError ("MeshFilter does not have a coresponding MeshRenderer.");
            continue; 
        }
        if (meshRenderer.materials.Length != meshFilter.sharedMesh.subMeshCount) {
            Debug.LogError ("Mismatch between material count and submesh count. Is this the correct MeshRenderer?"); 
            continue; 
        }

        for (int s = 0; s < meshFilter.sharedMesh.subMeshCount; s++) {
            int materialArrayIndex = 0;
            for (materialArrayIndex = 0; materialArrayIndex < materials.Count; materialArrayIndex++) {
                if (materials [materialArrayIndex] == meshRenderer.sharedMaterials ~~)~~

break;
}

if (materialArrayIndex == materials.Count) {
materials.Add (meshRenderer.sharedMaterials );
combineInstanceArrays.Add (new ArrayList ());
}

CombineInstance combineInstance = new CombineInstance ();
combineInstance.transform = myTransform * meshRenderer.transform.localToWorldMatrix;
combineInstance.subMeshIndex = s;
combineInstance.mesh = meshFilter.sharedMesh;
(combineInstanceArrays [materialArrayIndex] as ArrayList).Add (combineInstance);
}
}
// For MeshFilter
{
// Get / Create mesh filter
MeshFilter meshFilterCombine = gameObject.GetComponent ();
if (!meshFilterCombine)
meshFilterCombine = gameObject.AddComponent ();

// Combine by material index into per-material meshes
// also, Create CombineInstance array for next step
Mesh[] meshes = new Mesh[materials.Count];
CombineInstance[] combineInstances = new CombineInstance[materials.Count];

for (int m = 0; m < materials.Count; m++) {
CombineInstance[] combineInstanceArray = (combineInstanceArrays [m] as ArrayList).ToArray (typeof(CombineInstance)) as CombineInstance[];
meshes [m] = new Mesh ();
meshes [m].CombineMeshes (combineInstanceArray, true, true);
combineInstances [m] = new CombineInstance ();
combineInstances [m].mesh = meshes [m];
combineInstances [m].subMeshIndex = 0;
}

// Combine into one
meshFilterCombine.sharedMesh = new Mesh ();
meshFilterCombine.sharedMesh.CombineMeshes (combineInstances, false, false);

// Destroy other meshes
foreach (Mesh mesh in meshes) {
mesh.Clear ();
DestroyImmediate (mesh);
}
}

// For MeshRenderer
{
// Get / Create mesh renderer
MeshRenderer meshRendererCombine = gameObject.GetComponent ();
if (!meshRendererCombine)
meshRendererCombine = gameObject.AddComponent ();

// Assign materials
Material[] materialsArray = materials.ToArray (typeof(Material)) as Material[];
meshRendererCombine.materials = materialsArray;
}
}
}

3

Here is a component which combines meshes as I had originally intended - it works exactly as CombineMeshes but while taking into account different materials across different instances.

Note that it uses ArrayList instead of fixed sized arrays, which might be slower. But the alternative - getting the array size first - would require searching through the materials and submeshes twice, once for the array size, and again for filling the array. That probably would have wound up being slower.

Code is under construction - the only issue is that after you reference meshRenderer.materials[] or sharedMaterials[] the original instances are replaced with unique clones and thus materials[materialArrayIndex] == meshRenderer.sharedMaterials ~~will always be false. :frowning:~~
using UnityEngine;
using System;
using System.Collections;

public class CombineMeshes : MonoBehaviour {
public GameObject[] Objects;

[ContextMenu(“Combine”)]
public void Combine()
{
// Find all mesh filter submeshes and separate them by their cooresponding materials
ArrayList materials = new ArrayList();
ArrayList combineInstanceArrays = new ArrayList();

foreach( GameObject obj in Objects )
{
if(!obj)
continue;

MeshFilter[] meshFilters = obj.GetComponentsInChildren();

foreach( MeshFilter meshFilter in meshFilters )
{
MeshRenderer meshRenderer = meshFilter.GetComponent();

// Handle bad input
if(!meshRenderer) {
Debug.LogError(“MeshFilter does not have a coresponding MeshRenderer.”);
continue;
}
if(meshRenderer.materials.Length != meshFilter.sharedMesh.subMeshCount) {
Debug.LogError(“Mismatch between material count and submesh count. Is this the correct MeshRenderer?”);
continue;
}

for(int s = 0; s < meshFilter.sharedMesh.subMeshCount; s++)
{
int materialArrayIndex = 0;
for(materialArrayIndex = 0; materialArrayIndex < materials.Count; materialArrayIndex++)
{
if(materials[materialArrayIndex] == meshRenderer.sharedMaterials~~)
break;
}~~

if(materialArrayIndex == materials.Count)
{
materials.Add(meshRenderer.sharedMaterials~~);
combineInstanceArrays.Add(new ArrayList());
}~~

CombineInstance combineInstance = new CombineInstance();
combineInstance.transform = meshRenderer.transform.localToWorldMatrix;
combineInstance.subMeshIndex = s;
combineInstance.mesh = meshFilter.sharedMesh;
(combineInstanceArrays[materialArrayIndex] as ArrayList).Add( combineInstance );
}
}
}

// For MeshFilter
{
// Get / Create mesh filter
MeshFilter meshFilterCombine = gameObject.GetComponent();
if(!meshFilterCombine)
meshFilterCombine = gameObject.AddComponent();

// Combine by material index into per-material meshes
// also, Create CombineInstance array for next step
Mesh[] meshes = new Mesh[materials.Count];
CombineInstance[] combineInstances = new CombineInstance[materials.Count];

for( int m = 0; m < materials.Count; m++ )
{
CombineInstance[] combineInstanceArray = (combineInstanceArrays[m] as ArrayList).ToArray(typeof(CombineInstance)) as CombineInstance[];
meshes[m] = new Mesh();
meshes[m].CombineMeshes( combineInstanceArray, true, true );

combineInstances[m] = new CombineInstance();
combineInstances[m].mesh = meshes[m];
combineInstances[m].subMeshIndex = 0;
}

// Combine into one
meshFilterCombine.sharedMesh = new Mesh();
meshFilterCombine.sharedMesh.CombineMeshes( combineInstances, false, false );

// Destroy other meshes
foreach( Mesh mesh in meshes )
{
mesh.Clear();
DestroyImmediate(mesh);
}
}

// For MeshRenderer
{
// Get / Create mesh renderer
MeshRenderer meshRendererCombine = gameObject.GetComponent();
if(!meshRendererCombine)
meshRendererCombine = gameObject.AddComponent();

// Assign materials
Material[] materialsArray = materials.ToArray(typeof(Material)) as Material[];
meshRendererCombine.materials = materialsArray;
}
}
}
:slight_smile:

4

If you want a tool that do combine meshes and materials as well generating a texture atlas then GameDraw might be helpful to you!

Here is a video showing the combine meshes and materials feature in action:

and here is the link to the asset store:

6

"Code is under construction - the only issue is that after you reference meshRenderer.materials or sharedMaterials the original instances are replaced with unique clones and thus materials[materialArrayIndex] == meshRenderer.sharedMaterials will always be false. :("
Did you manage to solve this ?, other than that this is excellent code to combine meshes

9

There is a simple solution that can be use in editor mode.

using System.Collections.Generic;
using UnityEngine;

public static class MeshCombiner {
	public static void Combine(Transform parent) {
		Dictionary<Material, List<CombineInstance>> dictionary = new Dictionary<Material, List<CombineInstance>>();
		List<Material> materials = new List<Material>();

		MeshFilter[] meshFilters = parent.GetComponentsInChildren<MeshFilter>(true);

		for (int i = 0; i < meshFilters.Length; i++) {
			Material mat = meshFilters*.GetComponent<MeshRenderer>().sharedMaterial;*

  •  	if (!dictionary.ContainsKey(mat)) {*

  •  		dictionary.Add(mat, new List<CombineInstance>());*

  •  		materials.Add(mat);*

  •  	}*

  •  	dictionary[mat].Add(new CombineInstance {*

_ mesh = meshFilters*.sharedMesh,_
_ transform = meshFilters.transform.localToWorldMatrix*
* });
 }*_

* List combineInstances = new List();*
* foreach (var item in dictionary) {*
* Mesh mesh = new Mesh();*
* mesh.CombineMeshes(item.Value.ToArray());*
* mesh.Optimize();*
* combineInstances.Add(new CombineInstance {*
* mesh = mesh,*
* transform = parent.transform.localToWorldMatrix*
* });*
* }*

* Mesh newMesh = new Mesh() { name = “mesh” };*
* newMesh.CombineMeshes(combineInstances.ToArray(), false);*
* newMesh.Optimize();*

* GameObject newMeshObj = new GameObject(“newMesh”);*
* newMeshObj.transform.localPosition = Vector3.zero;*
* newMeshObj.AddComponent().materials = materials.ToArray();*
* newMeshObj.AddComponent().mesh = newMesh;*
* }*
}

10

One more suggestion for anyone coming here in the future if the other suggestions don’t suit you. You can do this very easily with the “Easy Mesh Combiner MT” plugin available in the Asset Store. Here is the link: Easy Mesh Combiner MT - Scene Mesh Merge, Atlasing Support & More | Game Toolkits | Unity Asset Store

8

Invaluable article . For what it’s worth , if someone have been needing to merge are interested in merging of , my colleagues came across a tool here altomerge.