MeshData

Description

A struct containing Mesh data for C# Job System access.

Use a MeshData struct to access, process and create Meshes in the C# Job System. There are two types of MeshData struct: read-only MeshData structs that allow read-only access to Mesh data from the C# Job System, and writeable MeshData structs that allow you to create Meshes from the C# Job System.

Read-only MeshData

When you pass one or more Meshes to Mesh.AcquireReadOnlyMeshData, Unity returns a MeshDataArray of read-only MeshData structs. You can access the resulting MeshDataArray and MeshData structs from any thread. Creating a MeshDataArray has some overhead for memory tracking and safety reasons, so it is more efficient to make a single call to Mesh.AcquireReadOnlyMeshData and request multiple MeshData structs in the same MeshDataArray than it is to make multiple calls to Mesh.AcquireReadOnlyMeshData.

Each MeshData struct contains a read-only snapshot of data for a given Mesh. You can use GetIndexData and GetVertexData to access the raw read-only Mesh data without any memory allocations, data copies or format conversions. You need to know the exact Mesh data layout to do this: for instance, the presence and formats of all the mesh vertex attributes. You can use GetColors, GetIndices, GetNormals, GetTangents, GetUVs, and GetVertices to copy the read-only Mesh data into pre-existing arrays. These methods also perform data format conversions if needed. For example, if the read-only MeshData struct uses VertexAttributeFormat.Float16 normals and you call GetNormals, the normals will be converted into Vector3 normals in the destination array.

You must dispose of the MeshDataArray once you have finished working with it. Calling Mesh.AcquireReadOnlyMeshData does not cause any memory allocations or data copies by default, as long as you dispose of the MeshDataArray before modifying the Mesh. However, if you call Mesh.AcquireReadOnlyMeshData and then modify the Mesh while the MeshDataArray exists, Unity must copy the MeshDataArray into a new memory allocation. In addition to this, if you call Mesh.AcquireReadOnlyMeshData and then modify the Mesh, your modifications are not reflected in the MeshData structs.

Use Dispose to dispose of the MeshDataArray, or use the C# using pattern to do this automatically:

using Unity.Collections;
using UnityEngine;
public class ExampleScript : MonoBehaviour
{
    void Start()
    {
        var mesh = new Mesh();
        mesh.vertices = new[] {Vector3.one, Vector3.zero};
        using (var dataArray = Mesh.AcquireReadOnlyMeshData(mesh))
        {
            var data = dataArray[0];
            // prints "2"
            Debug.Log(data.vertexCount);
            var gotVertices = new NativeArray<Vector3>(mesh.vertexCount, Allocator.TempJob);
            data.GetVertices(gotVertices);
            // prints "(1.0, 1.0, 1.0)" and "(0.0, 0.0, 0.0)"
            foreach (var v in gotVertices)
                Debug.Log(v);
            gotVertices.Dispose();
        }
    }
}

Writeable MeshData

Use Mesh.AllocateWritableMeshData to obtain a MeshDataArray of writeable MeshData structs. You can access the resulting MeshDataArray and MeshData structs from any thread. Creating a MeshDataArray has some overhead for memory tracking and safety reasons, so it is more efficient to make a single call to Mesh.AllocateWritableMeshData and request multiple MeshData structs in the same MeshDataArray than it is to make multiple calls to Mesh.AllocateWritableMeshData.

You can populate writeable MeshData structs with data to create new Meshes. Use Mesh.MeshData.SetVertexBufferParams to set the vertex buffer size and layout, and then write to the array returned by Mesh.MeshData.GetVertexData to set the vertices. Use Mesh.MeshData.SetIndexBufferParams to set the index buffer size and format, and then write to the array returned by Mesh.MeshData.GetIndexData to set the indices. Write to Mesh.MeshData.subMeshCount to set the number of sub meshes, and then use Mesh.MeshData.SetSubMesh to set sub mesh data.

When you have populated the writeable MeshData struct with your data, use Mesh.ApplyAndDisposeWritableMeshData to apply the data to Mesh objects and automatically dispose of the MeshDataArray.

using UnityEngine;
using UnityEngine.Rendering;
[RequireComponent(typeof(MeshFilter))]
public class ExampleScript : MonoBehaviour
{
    void Start()
    {
        // Allocate mesh data for one mesh.
        var dataArray = Mesh.AllocateWritableMeshData(1);
        var data = dataArray[0];
        // Tetrahedron vertices with positions and normals.
        // 4 faces with 3 unique vertices in each -- the faces
        // don't share the vertices since normals have to be
        // different for each face.
        data.SetVertexBufferParams(12,
            new VertexAttributeDescriptor(VertexAttribute.Position),
            new VertexAttributeDescriptor(VertexAttribute.Normal, stream: 1));
        // Four tetrahedron vertex positions:
        var sqrt075 = Mathf.Sqrt(0.75f);
        var p0 = new Vector3(0, 0, 0);
        var p1 = new Vector3(1, 0, 0);
        var p2 = new Vector3(0.5f, 0, sqrt075);
        var p3 = new Vector3(0.5f, sqrt075, sqrt075 / 3);
        // The first vertex buffer data stream is just positions;
        // fill them in.
        var pos = data.GetVertexData<Vector3>();
        pos[0] = p0; pos[1] = p1; pos[2] = p2;
        pos[3] = p0; pos[4] = p2; pos[5] = p3;
        pos[6] = p2; pos[7] = p1; pos[8] = p3;
        pos[9] = p0; pos[10] = p3; pos[11] = p1;
        // Note: normals will be calculated later in RecalculateNormals.
        // Tetrahedron index buffer: 4 triangles, 3 indices per triangle.
        // All vertices are unique so the index buffer is just a
        // 0,1,2,...,11 sequence.
        data.SetIndexBufferParams(12, IndexFormat.UInt16);
        var ib = data.GetIndexData<ushort>();
        for (ushort i = 0; i < ib.Length; ++i)
            ib[i] = i;
        // One sub-mesh with all the indices.
        data.subMeshCount = 1;
        data.SetSubMesh(0, new SubMeshDescriptor(0, ib.Length));
        // Create the mesh and apply data to it:
        var mesh = new Mesh();
        mesh.name = "Tetrahedron";
        Mesh.ApplyAndDisposeWritableMeshData(dataArray, mesh);
        mesh.RecalculateNormals();
        mesh.RecalculateBounds();
        GetComponent<MeshFilter>().mesh = mesh;
    }
}

Variables

Public Functions