## On this page

  

 

 # Test007

 Last update: 16.07.2025 

Instancing.

This example demonstrates a couple of different ways to do instancing. They both involve the re-using of Mesh object.

- Create a node and add it to a parent node, then add the parent node to its parent, ...
- Create a node and add it to a parent node, then create another node and add it to the same parent node, ...

The visibility selector in the first case will be multiple levels deep, and only a single level deep in the second case.

In either case the matrix associated with each node must be different so that the nodes do not draw in the same location as an other node. <script src="/ansys/nexus/viewer-loader.js"></script>

/\*

 \* Copyright 2018-2021 ANSYS, Inc. Unauthorized use, distribution, or duplication is prohibited.

 \* 

 \* Restricted Rights Legend

 \*

 \* Use, duplication, or disclosure of this

 \* software and its documentation by the

 \* Government is subject to restrictions as

 \* set forth in subdivision \[(b)(3)(ii)\] of

 \* the Rights in Technical Data and Computer

 \* Software clause at 52.227-7013.

 \*/

\#include <vector>

\#include <sstream>

 

\#include "GLTFWriter.h"

\#include "test.h"

 

using namespace ANSYS::Nexus;

 

// Replicated nodes

TESTFUNC(Instancing)

{

 GLTFWriter::GLTF *gltf = <a id="a0" name="a0"></a>[GLTFWriter::GLTF::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#ab7ba6d114c76cb60baf41aa6f13e9494)("MyApp", "1.0", functionName.c_str(), type);

 if (!gltf)

 throw std::runtime_error("Can't create GLTF");

 

 // SCENE

 GLTFWriter::Scene *scene = <a id="a1" name="a1"></a>[GLTFWriter::Scene::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_scene.xhtml#aac8bcb85d4361abba99053b3c56eb08b)(gltf, "TestScene", "m", 1.0, <a id="a2" name="a2"></a>[GLTFWriter::Scene::BT\_SOLID](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_scene.xhtml#ac17baf491cdba3613b0aa39719a3dbd8aeea551002921bb989b3ed35678ec982b), 0.5, 0.5, 0.5);

 if (!scene) {

 <a id="a3" name="a3"></a>[GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't create scene");

 }

 

 // LIGHTS

 {

 // LIGHT NODE

 GLTFWriter::Node *lightNode = <a id="a4" name="a4"></a>[GLTFWriter::Node::CreateLight](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_node.xhtml#a7883624afdcaae45b6018944a040a01c)(gltf);

 if (!lightNode || !scene-&gt;SetLight(lightNode)) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't create light");

 }

 

 // LIGHTS

 GLTFWriter::Light *light1 = <a id="a5" name="a5"></a>[GLTFWriter::Light::CreateAmbient](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_light.xhtml#a14a825d32570498d64b6a427fb4f8207)(gltf);

 lightNode-&gt;AppendLight(light1);

 

 GLTFWriter::Light *light2 = <a id="a6" name="a6"></a>[GLTFWriter::Light::CreateDirectional](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_light.xhtml#aa54e23609ac5f7a1a6808b62ee48163d)(gltf, 1, 1, 1, 0, 0, -1);

 lightNode-&gt;AppendLight(light2);

 }

 

 // CAMERA

 {

 // CAMERA

 GLTFWriter::Camera *camera = <a id="a7" name="a7"></a>[GLTFWriter::Camera::CreatePerspective](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_camera.xhtml#aff45bfb4357d46de63f59bb05473f527)(gltf);

 // CAMERA NODE

 std::vector&lt;double&gt; mat(16);

 mat[0] = 3;

 mat[1] = 0;

 mat[2] = 0;

 mat[3] = 0;

 mat[4] = 0;

 mat[5] = 3;

 mat[6] = 0;

 mat[7] = 0;

 mat[8] = 0;

 mat[9] = 0;

 mat[10] = 3;

 mat[11] = 0;

 mat[12] = 0;

 mat[13] = 0;

 mat[14] = 0;

 mat[15] = 1;

 GLTFWriter::Node *cameraNode = <a id="a8" name="a8"></a>[GLTFWriter::Node::CreateCamera](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_node.xhtml#af6c4767cc8271d9d39816d278538197a)(gltf, camera, "TestCamera", &amp;mat[0]);

 scene-&gt;SetCamera(cameraNode);

 }

 

 // CENTER

 {

 // NODE

 GLTFWriter::Node *node = <a id="a9" name="a9"></a>[GLTFWriter::Node::CreateMesh](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_node.xhtml#a4dd14791b2b9e65c115aa7a9e3f340e8)(gltf, "Center");

 if (!node || !scene-&gt;AppendMesh(node)) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't create mesh node");

 }

 

 // MESH

 GLTFWriter::Mesh *mesh = <a id="a10" name="a10"></a>[GLTFWriter::Mesh::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_mesh.xhtml#a9f7803b1b1eb72e4005665ca33f42788)(gltf);

 if (!mesh || !node-&gt;AppendMesh(mesh)) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't create mesh");

 }

 

 // PRIMITIVE

 std::pair&lt;GLTFWriter::Primitive *, GLTFWriter::Material *&gt; pm = GLTFWriter::Test::CreateSolidColoredSpherePrimitive(gltf, 0, 0, 0, 0.05F, 16, 1, 1, 1, 1);

 mesh-&gt;AppendPrimitive(pm.first);

 }

 

 const unsigned int numInstances = 6;

 

 // ONE WAY TO DO INSTANCING

 {

 // MESH

 GLTFWriter::Mesh *mesh = [GLTFWriter::Mesh::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_mesh.xhtml#a9f7803b1b1eb72e4005665ca33f42788)(gltf);

 {

 // PRIMITIVE

 std::pair&lt;GLTFWriter::Primitive *, GLTFWriter::Material *&gt; pm = GLTFWriter::Test::CreateColoredSpherePrimitive(gltf, 1, 0, 0, 0.5, 6);

 if (!pm.first || !pm.second || !mesh-&gt;AppendPrimitive(pm.first)) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't CreateColoredSpherePrimitive");

 }

 

 // this is a solid object, that we want to have an interior color so when it is clipped we see the solid interior color

 pm.second-&gt;AppendValue(<a id="a11" name="a11"></a>[GLTFWriter::Value::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_value.xhtml#aee78dae95614f843f10d5e19f9d55d61)(gltf, "solidColor", 0.4, 0.2, 0.4, 1.0));

 }

 

 GLTFWriter::Node *lastNode = 0;

 for (unsigned int i = numInstances; i &gt; 0; --i) {

 GLTFWriter::Test::Matrix4 mat; // identity

 GLTFWriter::Test::Matrix4 rot;

 if (i &gt; 1) {

 rot.LoadRotation(GLTFWriter::Test::Vector3(0, 0, 0), GLTFWriter::Test::Vector3(0, 0, 1), DegreesToRadians(360.0 / numInstances));

 mat *= rot;

 }

 

 std::ostringstream oss;

 oss &lt;&lt; "Node " &lt;&lt; i &lt;&lt; " + ";

 const std::string name = oss.str();

 GLTFWriter::Node *node = [GLTFWriter::Node::CreateMesh](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_node.xhtml#a4dd14791b2b9e65c115aa7a9e3f340e8)(gltf, name.c_str(), true, &amp;(mat.Get())[0]);

 if (!node || !node-&gt;AppendMesh(mesh)) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't create mesh node");

 }

 if (i != numInstances)

 node-&gt;AppendChild(lastNode);

 

 lastNode = node;

 }

 

 // NODE

 GLTFWriter::Node *node = [GLTFWriter::Node::CreateMesh](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_node.xhtml#a4dd14791b2b9e65c115aa7a9e3f340e8)(gltf, "INSTANCING 1");

 if (!node || !scene-&gt;AppendMesh(node)) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't create mesh node");

 }

 node-&gt;AppendChild(lastNode);

 }

 

 // ANOTHER WAY TO DO INSTANCING

 {

 // NODE

 GLTFWriter::Node *node = [GLTFWriter::Node::CreateMesh](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_node.xhtml#a4dd14791b2b9e65c115aa7a9e3f340e8)(gltf, "INSTANCING 2");

 if (!node || !scene-&gt;AppendMesh(node)) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't create mesh node");

 }

 

 GLTFWriter::Mesh *mesh = [GLTFWriter::Mesh::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_mesh.xhtml#a9f7803b1b1eb72e4005665ca33f42788)(gltf);

 if (!mesh) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't create mesh");

 }

 {

 // PRIMITIVE

 std::pair&lt;GLTFWriter::Primitive *, GLTFWriter::Material *&gt; pm = GLTFWriter::Test::CreateColoredSpherePrimitive(gltf, 2, 0, 0, 0.5, 6);

 if (!pm.first || !pm.second || !mesh-&gt;AppendPrimitive(pm.first)) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't CreateColoredSpherePrimitive");

 }

 

 // this is a solid object, that we want to have an interior color so when it is clipped we see the solid interior color

 pm.second-&gt;AppendValue([GLTFWriter::Value::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_value.xhtml#aee78dae95614f843f10d5e19f9d55d61)(gltf, "solidColor", 0.5, 0.5, 0.5, 1.0));

 }

 

 GLTFWriter::Test::Matrix4 mat; // identity

 GLTFWriter::Test::Matrix4 rot;

 rot.LoadRotation(GLTFWriter::Test::Vector3(0, 0, 0), GLTFWriter::Test::Vector3(0, 0, 1), DegreesToRadians(360.0 / numInstances));

 for (unsigned int i = 0; i &lt; numInstances; ++i) {

 if (i &gt; 0)

 mat *= rot;

 

 std::ostringstream oss;

 oss &lt;&lt; "Node " &lt;&lt; i + 1;

 const std::string name = oss.str();

 GLTFWriter::Node *lastNode = [GLTFWriter::Node::CreateMesh](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_node.xhtml#a4dd14791b2b9e65c115aa7a9e3f340e8)(gltf, name.c_str(), true, &amp;(mat.Get())[0]);

 if (!lastNode || !node-&gt;AppendChild(lastNode) || !lastNode-&gt;AppendMesh(mesh)) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Can't create mesh");

 }

 }

 }

 

 if (!gltf-&gt;Write()) {

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 throw std::runtime_error("Error creating file");

 }

 

 <a id="a12" name="a12"></a>[GLTFWriter::GLTF::GLTFError](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#acf83a4d185d959503cb9f3f2c2e9fafe) error = gltf-&gt;GetError();

 

 [GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)(gltf);

 

 if (error != <a id="a13" name="a13"></a>[GLTFWriter::GLTF::GLTF\_ERROR\_NONE](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#acf83a4d185d959503cb9f3f2c2e9fafea049c3b804e69ae05c02f4c2dedf4e0ea))

 throw std::runtime_error("Error creating file");

}

[ANSYS::Nexus::GLTFWriter::Camera::CreatePerspective](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_camera.xhtml#aff45bfb4357d46de63f59bb05473f527)

static Camera * CreatePerspective(GLTF *gltf, const char *name=0, float yfov=22.619864948, float aspectRatio=1, float zfar=100000, float znear=0.1)



[ANSYS::Nexus::GLTFWriter::GLTF::Destroy](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#a586171eb8e873e909db02a7eb4d80f5c)

static void Destroy(GLTF *gltf)



[ANSYS::Nexus::GLTFWriter::GLTF::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#ab7ba6d114c76cb60baf41aa6f13e9494)

static GLTF * Create(const char *application, const char *applicationVersion, const char *filePath, OutputType fileType=OT_AVZ)



[ANSYS::Nexus::GLTFWriter::GLTF::GLTFError](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#acf83a4d185d959503cb9f3f2c2e9fafe)

GLTFError

**Definition:** [GLTFGLTF.h:35](_g_l_t_f_g_l_t_f_8h_source.xhtml#l00035)



[ANSYS::Nexus::GLTFWriter::GLTF::GLTF\_ERROR\_NONE](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_g_l_t_f.xhtml#acf83a4d185d959503cb9f3f2c2e9fafea049c3b804e69ae05c02f4c2dedf4e0ea)

@ GLTF_ERROR_NONE

No Error.

**Definition:** [GLTFGLTF.h:36](_g_l_t_f_g_l_t_f_8h_source.xhtml#l00036)



[ANSYS::Nexus::GLTFWriter::Light::CreateAmbient](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_light.xhtml#a14a825d32570498d64b6a427fb4f8207)

static Light * CreateAmbient(GLTF *gltf, float colR=0.3, float colG=0.3, float colB=0.3)



[ANSYS::Nexus::GLTFWriter::Light::CreateDirectional](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_light.xhtml#aa54e23609ac5f7a1a6808b62ee48163d)

static Light * CreateDirectional(GLTF *gltf, float colR=1, float colG=1, float colB=1, float dirX=0, float dirY=0, float dirZ=-1, float specColR=1, float specColG=1, float specColB=1, float shininess=100)



[ANSYS::Nexus::GLTFWriter::Mesh::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_mesh.xhtml#a9f7803b1b1eb72e4005665ca33f42788)

static Mesh * Create(GLTF *gltf)



[ANSYS::Nexus::GLTFWriter::Node::CreateMesh](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_node.xhtml#a4dd14791b2b9e65c115aa7a9e3f340e8)

static Node * CreateMesh(GLTF *gltf, const char *name=0, bool visible=true, const double *matrix=0)



[ANSYS::Nexus::GLTFWriter::Node::CreateLight](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_node.xhtml#a7883624afdcaae45b6018944a040a01c)

static Node * CreateLight(GLTF *gltf)



[ANSYS::Nexus::GLTFWriter::Node::CreateCamera](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_node.xhtml#af6c4767cc8271d9d39816d278538197a)

static Node * CreateCamera(GLTF *gltf, Camera *camera, const char *name=0, const double *matrix=0)



[ANSYS::Nexus::GLTFWriter::Scene::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_scene.xhtml#aac8bcb85d4361abba99053b3c56eb08b)

static Scene * Create(GLTF *gltf, const char *name=0, const char *units=0, float scale=1, Scene::BackgroundType backgroundType=Scene::BT_NONE, float r1=0, float g1=0, float b1=0, float r2=0, float g2=0, float b2=0)



[ANSYS::Nexus::GLTFWriter::Scene::BT\_SOLID](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_scene.xhtml#ac17baf491cdba3613b0aa39719a3dbd8aeea551002921bb989b3ed35678ec982b)

@ BT_SOLID

Make solid color from color 1.

**Definition:** [GLTFScene.h:35](_g_l_t_f_scene_8h_source.xhtml#l00035)



[ANSYS::Nexus::GLTFWriter::Value::Create](class_a_n_s_y_s_1_1_nexus_1_1_g_l_t_f_writer_1_1_value.xhtml#aee78dae95614f843f10d5e19f9d55d61)

static Value * Create(GLTF *gltf, const char *name, const Value *value=0)