### CombineInstance Usage in Unity C# In Unity's Mesh Combination operations, `CombineInstance` plays a crucial role as part of the process to merge multiple meshes into one. This can lead to performance improvements by reducing draw calls which are often expensive due to state changes between rendering objects. The structure of `CombineInstance` allows developers to specify how individual mesh instances should contribute towards the final combined mesh: - The class contains properties such as `mesh`, `transform`, and others that define transformations applied when combining. - By setting these values appropriately before calling `Mesh.CombineMeshes()`, users control aspects like positioning, rotation, scaling for each sub-mesh within the larger composite model[^1]. Below is an example demonstrating how to use `CombineInstance` effectively with C# code in Unity: ```csharp using UnityEngine; public class MeshCombiner : MonoBehaviour { public GameObject[] objectsToCombine; void Start(){ CombineMeshes(); } void CombineMeshes(){ // Create array of combineInstances based on gameObjects count CombineInstance[] combine = new CombineInstance[objectsToCombine.Length]; int i=0; foreach(GameObject obj in objectsToCombine){ Renderer renderer = obj.GetComponent<Renderer>(); if(renderer != null && renderer.gameObject.activeSelf){ combine[i].mesh = renderer.sharedMesh; // Apply transformation from original object’s transform component combine[i].transform = obj.transform.localToWorldMatrix; ++i; } } // Assign resulting mesh back onto current GameObject's filter/meshRenderer components after combination MeshFilter mf = GetComponent<MeshFilter>(); if(mf == null){ mf = gameObject.AddComponent<MeshFilter>(); } mf.mesh = new Mesh(); mf.mesh.CombineMeshes(combine); MeshRenderer mr = GetComponent<MeshRenderer>(); if(mr == null){ mr = gameObject.AddComponent<MeshRenderer>(); } } } ``` This script iterates over specified child objects containing meshes, collects their data using `CombineInstance`, applies necessary transforms, then combines them all together under parent GameObject where this script resides. Afterward, it assigns newly created single mesh result directly to the parent instead of maintaining separate ones per child element[^4].