unsafe public OcclusionMesh(ref OcclusionMeshAsset sharedMesh, Occluder occluder)
        {
            vertexCount = sharedMesh.vertexCount;
            indexCount  = sharedMesh.indexCount;
            vertexData  = sharedMesh.vertexData;
            indexData   = sharedMesh.indexData;

            int size = UnsafeUtility.SizeOf <float4>() * vertexCount;
            var data = Memory.Unmanaged.Allocate(size, 64, Allocator.Persistent);

            transformedVertexData = BlobAssetReference <float4> .Create(data, size);

            screenMin = float.MaxValue;
            screenMax = -float.MaxValue;

            localToWorld = occluder.localTransform;
        }
        unsafe protected void AddComponents(Entity entity, Mesh mesh, int submeshIndex)
        {
            var subMesh            = mesh.GetSubMesh(submeshIndex);
            var verts              = mesh.vertices;
            var occlusionMeshAsset = new OcclusionMeshAsset();

            var vertices = new NativeArray <float4>(subMesh.vertexCount, Allocator.Temp);

            for (int i = 0; i < subMesh.vertexCount; ++i)
            {
                vertices[i] = new float4(verts[i + subMesh.firstVertex], 1.0f);
            }

            occlusionMeshAsset.vertexCount = subMesh.vertexCount;
            occlusionMeshAsset.vertexData  = BlobAssetReference <float4> .Create(
                vertices.GetUnsafeReadOnlyPtr(), sizeof(float4) *vertices.Length);

            vertices.Dispose();

            var indices = new NativeArray <int>(subMesh.indexCount, Allocator.Temp);

            fixed(int *srcIndices = mesh.triangles)
            {
                for (int i = 0; i < indices.Length; i++)
                {
                    indices[i] = srcIndices[subMesh.indexStart + i] - subMesh.firstVertex;
                    if (indices[i] < 0 || indices[i] > subMesh.vertexCount)
                    {
                        Debug.Log($"broken index at {i}: {indices[i]}");
                    }
                }
            }

            occlusionMeshAsset.indexCount = indices.Length;
            occlusionMeshAsset.indexData  = BlobAssetReference <int> .Create(
                indices.GetUnsafeReadOnlyPtr(), sizeof(int) *indices.Length);

            indices.Dispose();

            DstEntityManager.AddComponentData(entity, occlusionMeshAsset);
        }