Mesh.MeshData example

CreateOneMeshFromWholeScene.cs

using System.Collections.Generic;
using System.Diagnostics;
using Unity.Burst;
using Unity.Collections;
using Unity.Jobs;
using Unity.Mathematics;
using Unity.Profiling;
using UnityEngine;
using UnityEditor;
using UnityEngine.Rendering;
using Debug = UnityEngine.Debug;

public class CreateSceneMesh : MonoBehaviour
{
    static ProfilerMarker smp1 = new ProfilerMarker("Find Meshes");
    static ProfilerMarker smp2 = new ProfilerMarker("Prepare");
    static ProfilerMarker smp3 = new ProfilerMarker("Create Mesh");
    static ProfilerMarker smp4 = new ProfilerMarker("Cleanup");
    
    // ----------------------------------------------------------------------------------------------------------------
    // Mesh data API for creating meshes too
    // Took 0.11sec for 9009 objects, total 4460274 verts
    // Profiler: 114ms:
    // - Prepare 7.2ms
    // - SetVertexBufferParams 49ms (clearing memory... -- orthogonal issue, being fixed)
    // - Create Mesh / Jobs 57.9ms (each Job ~45-50ms)
    [MenuItem("Test/Create Mesh From Scene/New Create API %G")]
    public static void CreateMesh_05_MeshDataCreateApi()
    {
        var newGo = CreateMesh_05();

        Selection.activeObject = newGo;
    }
    
    [MenuItem("Test/Create Mesh From Scene/New Create API Bench")]
    public static void CreateMesh_05_MeshDataCreateApi_Bench()
    {
        for (int i = 0; i < 100; ++i)
        {
            var newGo = CreateMesh_05();
            DestroyImmediate(newGo);
        }
    }

    static GameObject CreateMesh_05()
    {
        var sw = Stopwatch.StartNew();
        smp1.Begin();
        var meshFilters = FindObjectsOfType<MeshFilter>();
        smp1.End();

        smp2.Begin();
        var jobs = new ProcessMeshDataJob05();
        jobs.vertexStart = new NativeArray<int>(meshFilters.Length, Allocator.TempJob, NativeArrayOptions.UninitializedMemory);
        jobs.triStart = new NativeArray<int>(meshFilters.Length, Allocator.TempJob, NativeArrayOptions.UninitializedMemory);
        jobs.xform = new NativeArray<float4x4>(meshFilters.Length, Allocator.TempJob, NativeArrayOptions.UninitializedMemory);
        var inputMeshes = new List<Mesh>(meshFilters.Length);
        
        int vertexStart = 0;
        int triStart = 0;
        int meshCount = 0;
        for (var i = 0; i < meshFilters.Length; ++i)
        {
            var mf = meshFilters[i];
            var go = mf.gameObject;
            if (go.CompareTag("EditorOnly"))
            {
                DestroyImmediate(go);
                continue;
            }

            var mesh = mf.sharedMesh;
            var vcount = mesh.vertexCount;
            var icount = (int)mesh.GetIndexCount(0);
            inputMeshes.Add(mesh);
            jobs.vertexStart[meshCount] = vertexStart;
            jobs.triStart[meshCount] = triStart;
            jobs.xform[meshCount] = go.transform.localToWorldMatrix;
            vertexStart += vcount;
            triStart += icount;
            ++meshCount;
        }
        smp2.End();

        jobs.meshData = Mesh.AcquireReadOnlyMeshData(inputMeshes);
        var outputMeshData = Mesh.AllocateWritableMeshData(1);
        
        jobs.outputMesh = outputMeshData[0];
        jobs.outputMesh.SetIndexBufferParams(triStart, IndexFormat.UInt32);
        jobs.outputMesh.SetVertexBufferParams(vertexStart,
            new VertexAttributeDescriptor(VertexAttribute.Position),
            new VertexAttributeDescriptor(VertexAttribute.Normal, stream:1));
        jobs.bounds = new NativeArray<float3x2>(meshCount, Allocator.TempJob, NativeArrayOptions.UninitializedMemory);
        for (var i = 0; i < meshCount; ++i)
            jobs.bounds[i] = new float3x2(new float3(Mathf.Infinity), new float3(Mathf.NegativeInfinity));
        
        var handle = jobs.Schedule(meshCount, 4);

        smp3.Begin();
        var newMesh = new Mesh();
        newMesh.name = "CombinedMesh";
        var sm = new SubMeshDescriptor(0, triStart, MeshTopology.Triangles);
        sm.firstVertex = 0;
        sm.vertexCount = vertexStart;
        
        handle.Complete();
        
        var bounds = new float3x2(new float3(Mathf.Infinity), new float3(Mathf.NegativeInfinity));
        for (var i = 0; i < meshCount; ++i)
        {
            var b = jobs.bounds[i];
            bounds.c0 = math.min(bounds.c0, b.c0);
            bounds.c1 = math.max(bounds.c1, b.c1);
        }

        sm.bounds = new Bounds((bounds.c0+bounds.c1)*0.5f, bounds.c1-bounds.c0);
        jobs.outputMesh.subMeshCount = 1;
        jobs.outputMesh.SetSubMesh(0, sm, MeshUpdateFlags.DontRecalculateBounds | MeshUpdateFlags.DontValidateIndices | MeshUpdateFlags.DontNotifyMeshUsers);
        Mesh.ApplyAndDisposeWritableMeshData(outputMeshData, new[]{newMesh}, MeshUpdateFlags.DontRecalculateBounds | MeshUpdateFlags.DontValidateIndices | MeshUpdateFlags.DontNotifyMeshUsers);
        newMesh.bounds = sm.bounds;
        smp3.End();
        smp4.Begin();
        jobs.meshData.Dispose();
        jobs.vertexStart.Dispose();
        jobs.triStart.Dispose();
        jobs.xform.Dispose();
        jobs.bounds.Dispose();
        
        smp4.End();
        
        var newGo = new GameObject("CombinedMesh", typeof(MeshFilter), typeof(MeshRenderer));
        newGo.tag = "EditorOnly";
        var newMf = newGo.GetComponent<MeshFilter>();
        var newMr = newGo.GetComponent<MeshRenderer>();
        newMr.material = AssetDatabase.LoadAssetAtPath<Material>("Assets/NewMat.mat");
        newMf.sharedMesh = newMesh;
        //newMesh.RecalculateNormals(); // faster to do normal xform in the job
        
        var dur = sw.ElapsedMilliseconds;
        Debug.Log($"Took {dur/1000.0:F2}sec for {meshCount} objects, total {vertexStart} verts");
        
        return newGo;
    }

    [BurstCompile]
    struct ProcessMeshDataJob05 : IJobParallelFor
    {
        [ReadOnly] public Mesh.MeshDataArray meshData;
        public Mesh.MeshData outputMesh;
        public NativeArray<int> vertexStart;
        public NativeArray<int> triStart;
        public NativeArray<float4x4> xform;
        public NativeArray<float3x2> bounds;

        public void Execute(int index)
        {
            var data = meshData[index]; 
            var vCount = data.vertexCount;
            var mat = xform[index];
            var vStart = vertexStart[index];
            
            var verts = new NativeArray<float3>(vCount, Allocator.Temp, NativeArrayOptions.UninitializedMemory);
            data.GetVertices(verts.Reinterpret<Vector3>());
            
            var normals = new NativeArray<float3>(vCount, Allocator.Temp, NativeArrayOptions.UninitializedMemory);
            data.GetNormals(normals.Reinterpret<Vector3>());
            
            var outputVerts = outputMesh.GetVertexData<Vector3>();
            var outputNormals = outputMesh.GetVertexData<Vector3>(stream:1);

            var b = bounds[index];
            for (var i = 0; i < vCount; ++i)
            {
                var pos = verts[i];
                pos = math.mul(mat, new float4(pos, 1)).xyz;
                outputVerts[i+vStart] = pos;
                var nor = normals[i];
                nor = math.normalize(math.mul(mat, new float4(nor, 0)).xyz);
                outputNormals[i+vStart] = nor;
                b.c0 = math.min(b.c0, pos);
                b.c1 = math.max(b.c1, pos);
            }
            bounds[index] = b;

            verts.Dispose();
            normals.Dispose();

            var tStart = triStart[index];
            var tCount = data.GetSubMesh(0).indexCount;
            var outputTris = outputMesh.GetIndexData<int>();
            if (data.indexFormat == IndexFormat.UInt16)
            {
                var tris = data.GetIndexData<ushort>();
                for (var i = 0; i < tCount; ++i)
                {
                    int idx = tris[i];
                    outputTris[i + tStart] = vStart + idx;
                }
            }
            else
            {
                var tris = data.GetIndexData<int>();
                for (var i = 0; i < tCount; ++i)
                {
                    int idx = tris[i];
                    outputTris[i + tStart] = vStart + idx;
                }
            }
        }
    }
    
    
    // ----------------------------------------------------------------------------------------------------------------
    // Took 0.71sec for 9010 objects, total 4460274 verts
    // Profiler: 670ms:
    // - Prepare 348ms (a lot of GC alloc/collect),
    // - Create Mesh 131ms,
    // - Recalculate Normals 188ms,
    [MenuItem("Test/Create Mesh From Scene/Classic Api %J")]
    public static void CreateMesh_01_ClassicApi()
    {
        var sw = Stopwatch.StartNew();
        smp1.Begin();
        var meshFilters = FindObjectsOfType<MeshFilter>();
        smp1.End();

        smp2.Begin();
        List<Vector3> allVerts = new List<Vector3>();
        //List<Vector3> allNormals = new List<Vector3>(); // faster to do RecalculateNormals than doing it manually
        List<int> allIndices = new List<int>();
        foreach (var mf in meshFilters)
        {
            var go = mf.gameObject;
            if (go.CompareTag("EditorOnly"))
            {
                DestroyImmediate(go);
                continue;
            }

            var tr = go.transform;
            var mesh = mf.sharedMesh;
            var verts = mesh.vertices;
            //var normals = mesh.normals;
            var tris = mesh.triangles;
            for (var i = 0; i < verts.Length; ++i)
            {
                var pos = verts[i];
                pos = tr.TransformPoint(pos);
                verts[i] = pos;
                //var nor = normals[i];
                //nor = tr.TransformDirection(nor).normalized;
                //normals[i] = nor;
            }
            var baseIdx = allVerts.Count;
            for (var i = 0; i < tris.Length; ++i)
                tris[i] = tris[i] + baseIdx;
            allVerts.AddRange(verts);
            //allNormals.AddRange(normals);
            allIndices.AddRange(tris);
        }
        smp2.End();

        smp3.Begin();
        var newMesh = new Mesh();
        newMesh.name = "CombinedMesh";
        newMesh.indexFormat = IndexFormat.UInt32;
        newMesh.SetVertices(allVerts);
        //newMesh.SetNormals(allNormals);
        newMesh.SetTriangles(allIndices, 0);
        smp3.End();
        
        var newGo = new GameObject("CombinedMesh", typeof(MeshFilter), typeof(MeshRenderer));
        newGo.tag = "EditorOnly";
        var newMf = newGo.GetComponent<MeshFilter>();
        var newMr = newGo.GetComponent<MeshRenderer>();
        newMr.material = AssetDatabase.LoadAssetAtPath<Material>("Assets/NewMat.mat");
        newMf.sharedMesh = newMesh;
        newMesh.RecalculateNormals();
        
        var dur = sw.ElapsedMilliseconds;
        Debug.Log($"Took {dur/1000.0:F2}sec for {meshFilters.Length} objects, total {allVerts.Count} verts");
        
        Selection.activeObject = newGo;
    }
}

Thank you for posting this. It's interesting to see exactly how other people are working with the Advanced Mesh API.

Trying to work through why meshes I build with the advanced API are not clickable in Scene View anymore. One clue is that when I turn on "Shaded Wireframe" as the view in Scene View none of the triangles are visible.