使用 Kanzi Engine API 创建网格¶
Mesh 存储用于渲染 Model3D 节点的几何数据。一个网格有一个或多个簇。每个簇都有一个材质和图元。图元通常是存储为顶点数据和索引数据的三角形。
您可以从 kzb 文件加载网格资源，或使用 Mesh::create 函数创建网格。在使用构造函数创建 Mesh 之后，Kanzi 将所有基本数据上传到 GPU 内存，而不是将数据存储在 Mesh 的 CPU 内存中。
要定义网格，您需要：
顶点格式定义。
此定义描述了定义顶点的组件。这包括有关顶点位置、纹理坐标、法线和切线的信息。
顶点列表。
每个顶点包含格式定义所描述的组件。
索引列表。
索引通过引用每个顶点的索引来描述多边形。当三角形描述一个多边形时，三个索引描述一个三角形。您可以使用多个索引列表，每个列表使用一种材料。
要启用 Kanzi Studio Preview 以可视化网格的边界体积，请为该网格设置边界框。请参阅 在 Preview 中分析您的应用程序。
创建网格¶
要使用 Kanzi Engine API 创建立方体网格：
// Define a CreateInfo structure and set it to not keep the data after uploading it to the GPU.
Mesh::CreateInfo createInfo;
createInfo.memoryType = GPUResource::GpuOnly;
// Describe the format for each vertex. In this example, every vertex has a position in 3D space,
// texture coordinates pointing to 2D texture space, and normal and tangent data in 3D space.
// Add a three-component position to the vertex format description.
// Use the standard Kanzi name kzPosition.
MeshVertexAttribute position("kzPosition", VertexAttribute::SemanticPosition, 0, GraphicsDataTypeSFLOAT32, 3, ~0u);
createInfo.vertexFormat.push_back(position);
// Add a two-component texture coordinate to the vertex format description.
// Texture coordinates enable you to use textures on a mesh.
// Use the standard Kanzi name kzTextureCoordinate0.
MeshVertexAttribute textureCoordinate("kzTextureCoordinate0", VertexAttribute::SemanticTextureCoordinate, 0, GraphicsDataTypeSFLOAT32, 2, ~0u);
createInfo.vertexFormat.push_back(textureCoordinate);
// Add three-component normals to the vertex format description.
// Normals enable you to use lighting on a mesh.
// Use the standard Kanzi name kzNormal.
MeshVertexAttribute normal("kzNormal", VertexAttribute::SemanticNormal, 0, GraphicsDataTypeSFLOAT32, 3, ~0u);
createInfo.vertexFormat.push_back(normal);
// Add three-component tangents to the vertex format description.
// Tangents enable you to use normal maps on a mesh.
// Use the standard Kanzi name kzTangent.
MeshVertexAttribute tangent("kzTangent", VertexAttribute::SemanticTangent, 0, GraphicsDataTypeSFLOAT32, 3, ~0u);
createInfo.vertexFormat.push_back(tangent);
// Now that you added all components to the vertex format description, update the offsets,
// strides, and vertex size.
updateVertexAttributeOffsetsAndVertexSize(createInfo);
updateVertexAttributeStrides(createInfo);
// Create a cluster. Two triangles define a face. Since a cube has six faces, you must create
// 36 indices (2 * 3 * 6 = 36). In this example, the entire mesh uses a single material, which
// is why you need only one cluster.
Mesh::CreateInfo::Cluster cluster(GraphicsPrimitiveTypeTriangles, 36, IndexBufferTypeUInt16, material, materialUrl);
createInfo.clusters.push_back(cluster);
// Create the vertices. Four vertices define one face of a cube. Since a cube has six faces,
// you must create 24 vertices (4 * 6 = 24). Here you create vertex faces with normals that
// point to the same direction. This makes the faces of a cube appear flat. You cannot reuse
// vertex positions because the normals for each face are separate.
{
createInfo.vertexCount = 24;
size_t dataSize = createInfo.vertexCount * createInfo.vertexSize;
createInfo.vertexData.resize(dataSize);
// Define the positions of the cube corners.
// This example first defines the back face, then the front face.
const Vector3 cornerPositions[] =
{
Vector3(1.0f, 1.0f, 1.0f),
Vector3(-1.0f, 1.0f, 1.0f),
Vector3(-1.0f, -1.0f, 1.0f),
Vector3(1.0f, -1.0f, 1.0f),
Vector3(1.0f, -1.0f, -1.0f),
Vector3(1.0f, 1.0f, -1.0f),
Vector3(-1.0f, 1.0f, -1.0f),
Vector3(-1.0f, -1.0f, -1.0f)
};
// Define texture UV coordinates for all faces.
const Vector2 UVs[] =
{
Vector2(1.0f, 1.0f),
Vector2(0.0f, 1.0f),
Vector2(0.0f, 0.0f),
Vector2(1.0f, 0.0f)
};
// Define vertex indices for all faces.
const unsigned int faceIndices[][4] =
{
// Front.
{ 0, 1, 2, 3 },
// Right.
{ 5, 0, 3, 4 },
// Back.
{ 6, 5, 4, 7 },
// Left.
{ 1, 6, 7, 2 },
// Top.
{ 5, 6, 1, 0 },
// Bottom.
{ 3, 2, 7, 4 }
};
// Define normals for each face.
const Vector3 faceNormals[] =
{
Vector3(0.0f, 0.0f, 1.0f),
Vector3(1.0f, 0.0f, 0.0f),
Vector3(0.0f, 0.0f, -1.0f),
Vector3(-1.0f, 0.0f, 0.0f),
Vector3(0.0f, 1.0f, 0.0f),
Vector3(0.0f, -1.0f, 0.0f)
};
// Define tangents for each face.
const Vector3 faceTangent[] =
{
Vector3(1.0f, 0.0f, 0.0f),
Vector3(0.0f, 0.0f, -1.0f),
Vector3(-1.0f, 0.0f, 0.0f),
Vector3(0.0f, 0.0f, 1.0f),
Vector3(1.0f, 0.0f, 0.0f),
Vector3(1.0f, 0.0f, 0.0f)
};
uint16_t vertexIndex = 0;
// To generate the vertex data, loop the data arrays that you defined above.
for (unsigned int face = 0; face < 6; ++face)
{
// Add two triangles.
uint16_t* indexData = reinterpret_cast<uint16_t*>(&createInfo.clusters[0].indexData[0]);
unsigned int faceBaseIndex = face * 6;
// The first three vertices of a face define the first triangle...
indexData[faceBaseIndex + 0] = vertexIndex + 0;
indexData[faceBaseIndex + 1] = vertexIndex + 1;
indexData[faceBaseIndex + 2] = vertexIndex + 2;
// ...and the second triangle uses the two last vertices of the face with the first vertex.
// These two triangles create a quad.
indexData[faceBaseIndex + 3] = vertexIndex + 2;
indexData[faceBaseIndex + 4] = vertexIndex + 3;
indexData[faceBaseIndex + 5] = vertexIndex + 0;
// Write vertices for the face.
for (unsigned int faceCorner = 0; faceCorner < 4; ++faceCorner, ++vertexIndex)
{
unsigned int boxCorner = faceIndices[face][faceCorner];
// Write the correct vertex for this corner of each face.
writeVertexAttribute(createInfo, vertexIndex, 0, cornerPositions[boxCorner]);
// UVs for each face are the same.
writeVertexAttribute(createInfo, vertexIndex, 1, UVs[faceCorner]);
// Normal is constant throughout the face.
writeVertexAttribute(createInfo, vertexIndex, 2, faceNormals[face]);
// Tangent is constant throughout the face.
writeVertexAttribute(createInfo, vertexIndex, 3, faceTangent[face]);
}
}
}
// Create a Box and set it as the bounding volume of the mesh.
// Position the box in the center of the mesh. Set the dimensions of the box along each axis
// to 2.0f, that is, from point (-1, -1, -1) to point (1, 1, 1) in the local coordinate space
// of the mesh.
createInfo.boundingBox = Box::fromCenterAndSize(Vector3(0.0f, 0.0f, 0.0f), Vector3(2.0f, 2.0f, 2.0f));
// Create a mesh from the data that you defined in the CreateInfo.
MeshSharedPtr mesh = Mesh::create(domain, createInfo, "box");
从本机句柄创建网格¶
您可以使用 Kanzi Engine API 从现有的 OpenGL 缓冲区句柄创建网格，并从现有网格中查询这些句柄。
要使用 Kanzi Engine API 从本机句柄创建立方体网格：
// Define a CreateInfo structure.
Mesh::CreateInfo createInfo;
// Create native handles for vertex and index buffers.
// Use buffer 0 for vertices and 1 for indices.
GPUBuffer::NativeHandle bufferHandles[2];
kzsGlGenBuffers(2, bufferHandles);
kzsGlBindBuffer(KZS_GL_ARRAY_BUFFER, bufferHandles[0]);
kzsGlBindBuffer(KZS_GL_ELEMENT_ARRAY_BUFFER, bufferHandles[1]);
createInfo.vertexBufferHandle = bufferHandles[0];
// Let the Mesh manage the handles from now on.
createInfo.takeOwnership = true;
// Describe the format for each vertex. In this example, every vertex has a position in 3D space,
// texture coordinates pointing to 2D texture space, and normal and tangent data in 3D space.
// Add a three-component position to the vertex format description.
// Use the standard Kanzi name kzPosition.
MeshVertexAttribute position("kzPosition", VertexAttribute::SemanticPosition, 0, GraphicsDataTypeSFLOAT32, 3, ~0u);
createInfo.vertexFormat.push_back(position);
// Add a two-component texture coordinate to the vertex format description.
// Texture coordinates enable you to use textures on a mesh.
// Use the standard Kanzi name kzTextureCoordinate0.
MeshVertexAttribute textureCoordinate("kzTextureCoordinate0", VertexAttribute::SemanticTextureCoordinate, 0, GraphicsDataTypeSFLOAT32, 2, ~0u);
createInfo.vertexFormat.push_back(textureCoordinate);
// Add three-component normals to the vertex format description.
// Normals enable you to use lighting on a mesh.
// Use the standard Kanzi name kzNormal.
MeshVertexAttribute normal("kzNormal", VertexAttribute::SemanticNormal, 0, GraphicsDataTypeSFLOAT32, 3, ~0u);
createInfo.vertexFormat.push_back(normal);
// Add three-component tangents to the vertex format description.
// Tangents enable you to use normal maps on a mesh.
// Use the standard Kanzi name kzTangent.
MeshVertexAttribute tangent("kzTangent", VertexAttribute::SemanticTangent, 0, GraphicsDataTypeSFLOAT32, 3, ~0u);
createInfo.vertexFormat.push_back(tangent);
// Now that you added all components to the vertex format description, update the offsets,
// strides, and vertex size.
updateVertexAttributeOffsetsAndVertexSize(createInfo);
updateVertexAttributeStrides(createInfo);
// Create a cluster. Two triangles define a face. Since a cube has six faces, you must create
// 36 indices (2 * 3 * 6 = 36). In this example, the entire mesh uses a single material, which
// is why you need only one cluster.
Mesh::CreateInfo::Cluster cluster(GraphicsPrimitiveTypeTriangles, 36, IndexBufferTypeUInt16, bufferHandles[1], material, materialUrl);
createInfo.clusters.push_back(cluster);
// Create the vertices. Four vertices define one face of a cube. Since cube has six faces,
// you must create 24 vertices (4 * 6 = 24). Here you create vertex faces with normals that
// point to the same direction. This makes the faces of a cube appear flat. You cannot reuse
// vertex positions because the normals for each face are separate.
{
createInfo.vertexCount = 24;
size_t dataSize = createInfo.vertexCount * createInfo.vertexSize;
// Define the positions of the cube corners.
// This example first defines the back face, then the front face.
const Vector3 cornerPositions[] = {
Vector3(1.0f, 1.0f, 1.0f),
Vector3(-1.0f, 1.0f, 1.0f),
Vector3(-1.0f, -1.0f, 1.0f),
Vector3(1.0f, -1.0f, 1.0f),
Vector3(1.0f, -1.0f, -1.0f),
Vector3(1.0f, 1.0f, -1.0f),
Vector3(-1.0f, 1.0f, -1.0f),
Vector3(-1.0f, -1.0f, -1.0f)
};
// Define texture UV coordinates for all faces.
const Vector2 UVs[] = {
Vector2(1.0f, 1.0f),
Vector2(0.0f, 1.0f),
Vector2(0.0f, 0.0f),
Vector2(1.0f, 0.0f)
};
// Define vertex indices for all faces.
const unsigned int faceIndices[][4] = {
// Front.
{ 0, 1, 2, 3 },
// Right.
{ 5, 0, 3, 4 },
// Back.
{ 6, 5, 4, 7 },
// Left.
{ 1, 6, 7, 2 },
// Top.
{ 5, 6, 1, 0 },
// Bottom.
{ 3, 2, 7, 4 }
};
// Define normals for all faces.
const Vector3 faceNormals[] = {
Vector3(0.0f, 0.0f, 1.0f),
Vector3(1.0f, 0.0f, 0.0f),
Vector3(0.0f, 0.0f, -1.0f),
Vector3(-1.0f, 0.0f, 0.0f),
Vector3(0.0f, 1.0f, 0.0f),
Vector3(0.0f, -1.0f, 0.0f)
};
// Define tangents for all faces.
const Vector3 faceTangent[] = {
Vector3(1.0f, 0.0f, 0.0f),
Vector3(0.0f, 0.0f, -1.0f),
Vector3(-1.0f, 0.0f, 0.0f),
Vector3(0.0f, 0.0f, 1.0f),
Vector3(1.0f, 0.0f, 0.0f),
Vector3(1.0f, 0.0f, 0.0f)
};
uint16_t vertexIndex = 0;
vector<uint16_t> indexBuffer;
indexBuffer.resize(createInfo.clusters[0].indexCount);
vector<uint8_t> vertexBuffer;
vertexBuffer.resize(dataSize);
uint8_t* vertexPtr = vertexBuffer.data();
// To generate the vertex data, loop the data arrays that you defined above.
for (unsigned int face = 0; face < 6; ++face)
{
// Add two triangles.
uint16_t* indexData = indexBuffer.data();
unsigned int faceBaseIndex = face * 6;
// The first three vertices of a face define the first triangle...
indexData[faceBaseIndex + 0] = vertexIndex + 0;
indexData[faceBaseIndex + 1] = vertexIndex + 1;
indexData[faceBaseIndex + 2] = vertexIndex + 2;
// ...and the second triangle uses the two last vertices of the face with the first vertex.
// These two triangles create a quad.
indexData[faceBaseIndex + 3] = vertexIndex + 2;
indexData[faceBaseIndex + 4] = vertexIndex + 3;
indexData[faceBaseIndex + 5] = vertexIndex + 0;
// Write vertices for the face.
for (unsigned int faceCorner = 0; faceCorner < 4; ++faceCorner, ++vertexIndex)
{
unsigned int boxCorner = faceIndices[face][faceCorner];
// Write the correct vertex for this corner of each face.
float* floatPtr = reinterpret_cast<float*>(vertexPtr);
*floatPtr++ = cornerPositions[boxCorner].getX();
*floatPtr++ = cornerPositions[boxCorner].getY();
*floatPtr++ = cornerPositions[boxCorner].getZ();
// UVs for each face are the same.
*floatPtr++ = UVs[faceCorner].getX();
*floatPtr++ = UVs[faceCorner].getY();
// Normal is constant throughout the face.
*floatPtr++ = faceNormals[face].getX();
*floatPtr++ = faceNormals[face].getY();
*floatPtr++ = faceNormals[face].getZ();
// Tangent is constant throughout the face.
*floatPtr++ = faceTangent[face].getX();
*floatPtr++ = faceTangent[face].getY();
*floatPtr++ = faceTangent[face].getZ();
vertexPtr += createInfo.vertexSize;
}
}
kzsGlBufferData(KZS_GL_ARRAY_BUFFER, static_cast<int>(vertexBuffer.size()), vertexBuffer.data(), KZS_GL_STATIC_DRAW);
kzsGlBufferData(KZS_GL_ELEMENT_ARRAY_BUFFER, static_cast<int>(indexBuffer.size() * sizeof(uint16_t)), indexBuffer.data(), KZS_GL_STATIC_DRAW);
}
// Create a Box and set it as the bounding volume of the mesh.
// Position the box in the center of the mesh. Set the dimensions of the box along each axis
// to 2.0f, that is, from point (-1, -1, -1) to point (1, 1, 1) in the local coordinate space
// of the mesh.
createInfo.boundingBox = Box::fromCenterAndSize(Vector3(0.0f, 0.0f, 0.0f), Vector3(2.0f, 2.0f, 2.0f));
// Create a mesh from the data that you defined in the CreateInfo.
MeshSharedPtr mesh = Mesh::create(domain, createInfo, "box");
有关详细信息，请参阅 Mesh 类。
使用实例化创建网格¶
当您渲染大量相同网格的副本时，为每个副本执行绘制调用会消耗 GPU 时间并降低应用程序性能。实例化使得可以通过单个渲染调用绘制具有不同属性（例如位置、大小和颜色）的多个网格副本。
此示例在不同位置和不同颜色下渲染四个实例的立方体网格。
使用 Kanzi Engine API 创建具有实例化的立方体网格：
// Create a custom shader to use instanced attributes.
const char* vertexSource =
"#version 100\n"
"attribute vec3 kzPosition;\n"
"attribute vec3 InstancePosition;\n"
"attribute vec4 InstanceColor;\n"
"uniform highp mat4 kzProjectionCameraWorldMatrix;\n"
"varying vec4 outColor;\n"
"void main() {\n"
"precision mediump float;\n"
"vec3 position = kzPosition + InstancePosition;\n"
"gl_Position = kzProjectionCameraWorldMatrix * vec4(position, 1.0);\n"
"outColor = InstanceColor;\n"
"}\n";
const char* fragmentSource =
"#version 100\n"
"varying vec4 outColor;\n"
"void main() {\n"
"precision lowp float;\n"
"gl_FragColor = outColor;\n"
"}\n";
ShaderProgram::CreateInfoShaderSources shaderCreateInfo(vertexSource, fragmentSource);
static const ShaderVertexAttribute kzPosition = ShaderVertexAttribute("kzPosition", VertexAttribute::SemanticPosition,
0, GraphicsElementTypeFLOAT, 0, 3, 0, 0);
static const ShaderVertexAttribute InstancePosition = ShaderVertexAttribute("InstancePosition", VertexAttribute::SemanticPosition,
1, GraphicsElementTypeFLOAT, 0, 3, 1, 0);
static const ShaderVertexAttribute InstanceColor = ShaderVertexAttribute("InstanceColor", VertexAttribute::SemanticColor,
0, GraphicsElementTypeFLOAT, 0, 4, 2, 0);
shaderCreateInfo.vertexFormat.push_back(kzPosition);
shaderCreateInfo.vertexFormat.push_back(InstancePosition);
shaderCreateInfo.vertexFormat.push_back(InstanceColor);
shaderCreateInfo.addFixedUniform("kzProjectionCameraWorldMatrix");
auto shader = ShaderProgram::create(domain, shaderCreateInfo, "CustomShader");
auto material = Material::create(domain, "CustomMaterial", shader);
// Define a CreateInfo structure and set it to not keep the data after uploading it to the GPU.
Mesh::CreateInfo createInfo;
createInfo.memoryType = GPUResource::GpuOnly;
// Describe the format for each vertex. In this example, every vertex has a position in 3D space,
// and every instance has a position in 3D space and a color.
// Add a three-component position to the vertex format description.
// Use the standard Kanzi name kzPosition.
MeshVertexAttribute position("kzPosition", VertexAttribute::SemanticPosition, 0, GraphicsDataTypeSFLOAT32, 3, ~0u);
createInfo.vertexFormat.push_back(position);
// Add instance position.
MeshVertexAttribute instancePosition("InstancePosition", VertexAttribute::SemanticPosition, 1, GraphicsDataTypeSFLOAT32, 3, 0);
instancePosition.divisor = 1;
createInfo.vertexFormat.push_back(instancePosition);
// Add instance color.
MeshVertexAttribute instanceColor("InstanceColor", VertexAttribute::SemanticColor, 0, GraphicsDataTypeUNORM8, 4, 3 * sizeof(float));
instanceColor.divisor = 1;
createInfo.vertexFormat.push_back(instanceColor);
// Now that you added all components to the vertex format description, update the offsets,
// strides, and sizes.
updateVertexAttributeOffsetsAndVertexSize(createInfo);
updateVertexAttributeStrides(createInfo);
// Create a cluster. Two triangles define a face. Since a cube has six faces, you must create
// 36 indices (2 * 3 * 6 = 36). In this example, the entire mesh uses a single material, which
// is why you need only one cluster.
Mesh::CreateInfo::Cluster cluster(GraphicsPrimitiveTypeTriangles, 36, IndexBufferTypeUInt16, material, "");
createInfo.clusters.push_back(cluster);
// Create the vertices. In this example, faces share vertices, so you need only eight vertices.
{
createInfo.vertexCount = 8;
size_t dataSize = createInfo.vertexCount * createInfo.vertexSize;
createInfo.vertexData.resize(dataSize);
// Define the positions of the cube corners.
// This example first defines the back face, then the front face.
const Vector3 cornerPositions[] = {
Vector3(1.0f, 1.0f, 1.0f),
Vector3(-1.0f, 1.0f, 1.0f),
Vector3(-1.0f, -1.0f, 1.0f),
Vector3(1.0f, -1.0f, 1.0f),
Vector3(1.0f, -1.0f, -1.0f),
Vector3(1.0f, 1.0f, -1.0f),
Vector3(-1.0f, 1.0f, -1.0f),
Vector3(-1.0f, -1.0f, -1.0f)
};
// Define vertex indices for all faces.
const uint16_t faceIndices[][4] = {
// Front.
{ 0, 1, 2, 3 },
// Right.
{ 5, 0, 3, 4 },
// Back.
{ 6, 5, 4, 7 },
// Left.
{ 1, 6, 7, 2 },
// Top.
{ 5, 6, 1, 0 },
// Bottom.
{ 3, 2, 7, 4 }
};
// To generate the vertex data, loop the data arrays that you defined above.
for (unsigned int face = 0; face < 6; ++face)
{
// Add two triangles.
uint16_t* indexData = reinterpret_cast<uint16_t*>(&createInfo.clusters[0].indexData[0]);
unsigned int faceBaseIndex = face * 6;
// The first three vertices of a face define the first triangle...
indexData[faceBaseIndex + 0] = faceIndices[face][0];
indexData[faceBaseIndex + 1] = faceIndices[face][1];
indexData[faceBaseIndex + 2] = faceIndices[face][2];
// ...and the second triangle uses the two last vertices of the face with the first vertex.
// These two triangles create a quad.
indexData[faceBaseIndex + 3] = faceIndices[face][2];
indexData[faceBaseIndex + 4] = faceIndices[face][3];
indexData[faceBaseIndex + 5] = faceIndices[face][0];
}
// Write vertices.
for (unsigned int vertexIndex = 0; vertexIndex < 8; ++vertexIndex)
{
// Write the correct vertex for this corner of each face.
writeVertexAttribute(createInfo, vertexIndex, 0, cornerPositions[vertexIndex]);
}
}
// Create the instance data: float position vector with three components and packed
// 32-bit color per instance.
{
// Create four instances of the cube.
createInfo.instanceCount = 4;
createInfo.instanceData.resize(createInfo.instanceCount * createInfo.instanceSize);
// Define the positions.
const Vector3 instancePositions[] = {
Vector3(-1.0f, -1.0f, 0.0f),
Vector3(-1.0f, 1.0f, 0.0f),
Vector3(1.0f, 1.0f, 0.0f),
Vector3(1.0f, -1.0f, 0.0f)
};
// Define the colors: white, red, green, blue.
const uint32_t instanceColors[] = {
0xffffffff,
0xffff0000,
0xff00ff00,
0xff0000ff
};
byte* instanceBuffer = createInfo.instanceData.data();
for (unsigned instance = 0; instance < createInfo.instanceCount; ++instance)
{
// Copy the positions and colors to the instance data buffer.
auto pos = reinterpret_cast<float*>(instanceBuffer + instance * createInfo.instanceSize);
*pos++ = instancePositions[instance].getX();
*pos++ = instancePositions[instance].getY();
*pos++ = instancePositions[instance].getZ();
auto color = reinterpret_cast<uint32_t*>(pos);
*color = instanceColors[instance];
}
}
// Create a Box and set it as the bounding volume of the mesh.
// Position the box in the center of the mesh. Set the dimensions of the box along each axis
// to 4.0f, that is, from point (-2, -2, -1) to point (2, 2, 1) in the local coordinate space
// of the mesh. This includes all the instances.
createInfo.boundingBox = Box::fromCenterAndSize(Vector3(0.0f, 0.0f, 0.0f), Vector3(4.0f, 4.0f, 2.0f));
// Create a mesh from the data that you defined in the CreateInfo.
MeshSharedPtr mesh = Mesh::create(domain, createInfo, "instancedBox");