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2. Creating and Deleting Nodes at Runtime

Warning
The scope of applications for UnigineScript is limited to implementing materials-related logic (material expressions, scriptable materials, brush materials). Do not use UnigineScript as a language for application logic, please consider C#/C++ instead, as these APIs are the preferred ones. Availability of new Engine features in UnigineScipt (beyond its scope of applications) is not guaranteed, as the current level of support assumes only fixing critical issues.

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Nodes can be created and deleted at runtime almost as easy as in the Editor. The basic set of actions is as follows:

  • Creation. To create a node we should call a constructor of the corresponding class by using the new keyword and providing construction parameters if necessary.
  • Deletion. To delete a node we invoke a destructor explicitly by simply calling delete for the node we are going to remove.
Source code (UnigineScript)
// creating a node of the NodeType named nodename
<NodeType> nodename = new <NodeType>(<construction_parameters>);
	
// removing the node
delete nodename;

Now let us illustrate the process of creating and deleting a node using a simple static mesh (ObjectMeshStatic) by both creating a box surface and loading a mesh from an asset as an example.

Source code (UnigineScript)
#include <core/unigine.h>

int init() {
	// first, we&apos;re creating a mesh instance as it is required to call an ObjectMeshStatic constructor
	Mesh mesh = new Mesh();

	// loading a mesh from an fbx model imported to the data/fbx/ folder using the Editor
	mesh.load("material_ball.mesh");

	// creating a box surface with a given size to the mesh
	mesh.addBoxSurface("box_surface", vec3(0.5f, 0.5f, 0.5f));

	//create an ObjectMeshStatic node
	ObjectMeshStatic my_object = new ObjectMeshStatic(mesh);

	// removing the node
	delete my_object;

	// clearing the mesh
	mesh.clear();

	return 1;
}

Additional information:

Project Progress#

In our project we are going to need some objects, so let us:

  • write an auxiliary method to create an ObjectMeshDynamic node (addMeshToScene),
  • write an auxiliary method to append some initial set of objects to our scene(initObjects),
  • store the list of nodes created at runtime in a Vector.

In the AppWorldLogic.h file, we include the UnigineObjects.h library to work with ObjectMeshDynamic class, define the scene objects vector and declare our methods: addMeshToScene and initObjects.

Source code (C++)
// AppWorldLogic.h

#include <UnigineObjects.h>

using namespace Unigine;

/* ... */

class AppWorldLogic : public WorldLogic {
	
public:

/* .. */

private:

/* .. */

	// auxiliary functions
	int addMeshToScene(const char *file_name, const char *mesh_name, const char *material_name, Math::Vec3 position);
	int initObjects();
	
/* .. */	
	
	// scene objects vector
	Vector<ObjectMeshDynamicPtr> Objects;
	
/* .. */	
};

In the AppWorldLogic.cpp file let us implement our methods and insert initObjects method into the AppWorldLogic::init() method. We are also going to do some cleanup (delete all created nodes) in the AppWorldLogic::shutdown() method.

Source code (C++)
// AppWorldLogic.cpp
/* .. */

/// method adding a Dynamic Mesh Object to the scene. 
/// if an empty filename is passed the method creates a default box; 
/// otherwise, loads a mesh-file with a given name.
int AppWorldLogic::addMeshToScene(const char *file_name, const char *mesh_name, const char *material_name, Math::Vec3 position)
{
	MeshPtr mesh = Mesh::create();
	ObjectMeshDynamicPtr omd;

	if (file_name){				// loading a mesh from a specified file
		if (!mesh->load(file_name))
		{
			Log::error("\nError opening .mesh file!\n");
			mesh.clear();
			
			return 0;
		}
		else omd = ObjectMeshDynamic::create(mesh);
	}
	else								//creating a default box
	{
		mesh->addBoxSurface("box_surface", Math::vec3(0.5f, 0.5f, 0.5f));

		omd = ObjectMeshDynamic::create(mesh);
	}
	
	// setting node material, name and transformation
	omd->setMaterial(material_name, "*");
	omd->setName(mesh_name);
	omd->setWorldPosition(position);

	// updating the list of scene objects
	Objects.append(omd);

	//reporting progress to the console
	Log::message("-> Object %s added to the scene.\n", mesh_name);

	// clearing the mesh
	mesh.clear();

	return 1;
}

/* .. */

/// method performing initialization of objects
int AppWorldLogic::initObjects()
{
	int index = 0;
	for (int x = 0; x < 2; x++)
	{
		for (int y = 0; y < 2; y++)
		{
			addMeshToScene(NULL, String::format("my_meshdynamic_%d", index), "mesh_base", Math::Vec3(x, y, 1.0f));
			index++;
		}
	}
	// reporting progress to the console
	Log::warning("Objects generation OK!\n\n");
	
	return 1;
}

/* .. */
	
int AppWorldLogic::init() 
{

	// creating objects
	initObjects();

/* .. */
	
	return 1;
}

/* .. */

int AppWorldLogic::shutdown() {
	
	// deleting all created nodes
	for(int i = 0; i < Objects.size(); i++)
	{
		// removing current node from the scene
		Objects[i].deleteLater();
	}
	
	// updating the list of scene objects
	Objects.clear();

	return 1;
}
/* .. */

Source Files

You can copy the code below and paste it to the corresponding source files of your project:

AppWorldLogic.h

Source code (C++)
#ifndef __APP_WORLD_LOGIC_H__
#define __APP_WORLD_LOGIC_H__

#include <UnigineLogic.h>
#include <UnigineStreams.h>
#include <UnigineObjects.h>

using namespace Unigine;

class AppWorldLogic : public WorldLogic {
	
public:
	AppWorldLogic();
	virtual ~AppWorldLogic();
	
	virtual int init();
	
	virtual int update();
	virtual int postUpdate();
	virtual int updatePhysics();
	
	virtual int shutdown();
	
	virtual int save(const StreamPtr &stream);
	virtual int restore(const StreamPtr &stream);
private:

	//auxiliary functions
	int addMeshToScene(const char *file_name, const char *mesh_name, const char *material_name, Math::Vec3 position);

	// initialization functions
	int initObjects();

	// scene objects vector
	Vector<ObjectMeshDynamicPtr> Objects;
};

#endif // __APP_WORLD_LOGIC_H__

AppWorldLogic.cpp

Source code (C++)
#include "AppWorldLogic.h"
// World logic, it takes effect only when the world is loaded.
// These methods are called right after corresponding world script's (UnigineScript) methods.
//-----------------------------------------------------------------------------------------------------------------------------
//---------------------------------------------- AUXILIARY FUNCTIONS AND METHODS ----------------------------------------------
//-----------------------------------------------------------------------------------------------------------------------------

/// method adding a Dynamic Mesh Object to the scene. If an empty filename is passed the method creates a default box; otherwise, loads a mesh-file with a given name.
int AppWorldLogic::addMeshToScene(const char *file_name, const char *mesh_name, const char *material_name, Math::Vec3 position)
{
	MeshPtr mesh = Mesh::create();
	ObjectMeshDynamicPtr omd;

	if (file_name) {				// loading a mesh from a specified file
		if (!mesh->load(file_name))
		{
			Log::error("\nError opening .mesh file!\n");
			mesh.clear();

			return 0;
		}
		else omd = ObjectMeshDynamic::create(mesh);
	}
	else																// creating a default box
	{
		mesh->addBoxSurface("box_surface", Math::vec3(0.5f));

		omd = ObjectMeshDynamic::create(mesh);
	}

	// setting node material, name and position
	omd->setMaterial(material_name, "*");
	omd->setName(mesh_name);
	omd->setWorldPosition(position);

	// updating the list of scene objects
	Objects.append(omd);

	// reporting progress to the console
	Log::message("-> Object %s added to the scene.\n", mesh_name);

	// clearing the mesh
	mesh.clear();

	return 1;

}
//-----------------------------------------------------------------------------------------------------------------------------
//---------------------------------------------- INITIALIZATION METHODS -------------------------------------------------------
//-----------------------------------------------------------------------------------------------------------------------------
/// method performing initialization of the set of 4 boxes
int AppWorldLogic::initObjects()
{
	int index = 0;

	for (int x = 0; x < 2; x++)
	{
		for (int y = 0; y < 2; y++)
		{
			addMeshToScene(NULL, String::format("my_meshdynamic_%d", index), "mesh_base", Math::Vec3(x, y, 1.0f));
			index++;
		}
	}

	// reporting progress to the console
	Log::warning("Objects generation OK!\n\n");

	return 1;
}
//-----------------------------------------------------------------------------------------------------------------------------
AppWorldLogic::AppWorldLogic() {

}

AppWorldLogic::~AppWorldLogic() {

}

int AppWorldLogic::init() {
	// Write here code to be called on world initialization: initialize resources for your world scene during the world start.

	// creating objects
	initObjects();

	return 1;
}

// start of the main loop
int AppWorldLogic::update() {
	// Write here code to be called before updating each render frame: specify all graphics-related functions you want to be called every frame while your application executes.

	return 1;
}

int AppWorldLogic::postUpdate() {
	// The engine calls this function before rendering each render frame: correct behavior after the state of the node has been updated.

	return 1;
}

int AppWorldLogic::updatePhysics() {
	// Write here code to be called before updating each physics frame: control physics in your application and put non-rendering calculations.
	// The engine calls updatePhysics() with the fixed rate (60 times per second by default) regardless of the FPS value.
	// WARNING: do not create, delete or change transformations of nodes here, because rendering is already in progress.

	return 1;
}
// end of the main loop

int AppWorldLogic::shutdown() {

	// deleting all created nodes
	for (int i = 0; i < Objects.size(); i++)
	{
		// removing current node from the scene
		Objects[i]->deleteLater();
	}

	// updating the list of scene objects
	Objects.clear();

	return 1;
}

int AppWorldLogic::save(const StreamPtr &stream) {
	// Write here code to be called when the world is saving its state (i.e. state_save is called): save custom user data to a file.

	UNIGINE_UNUSED(stream);
	return 1;
}

int AppWorldLogic::restore(const StreamPtr &stream) {
	// Write here code to be called when the world is restoring its state (i.e. state_restore is called): restore custom user data to a file here.

	UNIGINE_UNUSED(stream);
	return 1;
}


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Last update: 2020-07-31
Build: ()