Combining Meshes with subMeshes

Question

How do you combine meshes with submeshes?

I have two meshes, and each mesh has two submeshes. What I want, after combining them, is one mesh, and two submeshes.

Answer 1

I commented on the previous answer, but I just tested my theory and it seems to work. To recap: I create a NEW mesh for each sub-mesh in an original mesh. I then combine these (sub-mesh) meshes. So for 4 objects that use identical 2-sub-mesh meshes, instead of getting a single combined mesh with 8 sub-meshes, I get 2 combined meshes, with 1 "sub-mesh" each. This brings my draw calls down from 17 to 6, in my test case.

Briefly, I performed 4 steps to combine objects that use meshes with multiple sub-meshes:

Gather a list of GameObjects that I wish to combine.
Go through each mesh filter in the GameObject list from step 1. Create and cache newly constructed Meshes from each sub-mesh (I used this: http://www.unifycommunity.com/wiki/index.php?title=MeshCreationHelper).
For each mesh filter, create a list of CombineInstance data for EACH sub-mesh of the mesh. You'll want the CombineInstance.mesh to point to the cached (sub-mesh) Mesh created in step 2.
For each sub-mesh list of CombineInstances, perform the combine.

Sorry if the wording is poor. Hope this helps.

Update: There appears to be a bug with the MeshCreationHelper script that I linked to above. I don't believe it's properly constructing the new triangle list. I edited the wiki discussion for that page, so you can view my suggested change via the discussion:

http://www.unifycommunity.com/wiki/index.php?title=Talk:MeshCreationHelper

Answer 2

just found this question using google, and i found a simpler answer while trying to figure this out:

you can use the .subMeshIndex property on your CombineInstance-s, so for each submesh you want to combine you need to add a CombineInstance with the correct subMeshIndex.

this is how i did it:

(the script is placed on a parent GO, with an empty mesh filter, and a mesh renderer. the script combines child meshes on awake, while keeping the mesh in the same position as the originals were. the resulting mesh uses only 1 material)

         void Awake ()
         {
             // save the parent GO-s pos+rot
             Vector3 position = transform.position;
             Quaternion rotation = transform.rotation;
 
             // move to the origin for combining
             transform.position = Vector3.zero;
             transform.rotation = Quaternion.identity;
 
             MeshFilter[] filters = GetComponentsInChildren<MeshFilter> ();
             List<CombineInstance> combine = new List<CombineInstance> ();
 
             for (int i = 0; i < filters.Length; i++)
             {
                 // skip the empty parent GO
                 if (filters[i].sharedMesh == null)
                     continue;
 
                 // combine submeshes
                 for (int j = 0; j < filters[i].sharedMesh.subMeshCount; j++)
                 {
                     CombineInstance ci = new CombineInstance ();
 
                     ci.mesh = filters[i].sharedMesh;
                     ci.subMeshIndex = j;
                     ci.transform = filters[i].transform.localToWorldMatrix;
 
                     combine.Add (ci);
                 }                
 
                 // disable child mesh GO-s
                 filters[i].gameObject.SetActive (false);
             }
 
             MeshFilter filter = GetComponent<MeshFilter> ();
             filter.mesh = new Mesh ();
             filter.mesh.CombineMeshes (combine.ToArray (), true, true);
 
             // restore the parent GO-s pos+rot
             transform.position = position;
             transform.rotation = rotation;
         }

Answer 3

Answer by Ashkan_gc · Jan 16, 2010 at 06:30 PM

you can combine meshes with with combinechildren script in standard assets. if you import standard assets you can find it in component menu in mesh sub menu. you can combine a mesh with it's children with this script. you can easily modify the code to do what you want because the main part of this script is the function that combines two meshes.

0 Show 3 · Share

Tempest · Jan 16, 2010 at 07:19 PM 0

Share

I understand thoroughly how to combine two meshes. What I am looking for is the specific way in which you combine them while keeping the submeshes persistent.

duck ♦♦ · Jan 16, 2010 at 07:47 PM 0

Share

Could you describe the results that you're getting currently, when you use combine children?

mstultz · Apr 27, 2010 at 04:53 PM 0

Share

I've run into the same issue myself. My current thought is that perhaps it is possible to extract the submeshes into their own mesh, and then combine those. So I have 4 instances of a 2-submesh mesh. Right now I have a combined (1) mesh of 8 submeshes (8 draws). I'm hoping I can get a final result of 2 combined meshes that consist of one sub-mesh each (2 draws).

Combining Meshes with subMeshes

3 Replies

Your answer

Welcome to Unity Answers

Follow this Question

Related Questions