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12. Making It in Time

<< RETURN TO THE PREVIOUS SECTION

As the frame rate of our application may vary (i.e. the AppWorldLogic::update() method will be called more or less frequently) depending on hardware, we should do something to ensure that certain actions are performed at the same time periods regardless of the frame rate (e.g. change something once per second etc). To make your game frame rate independent you can use the a scaling multiplier (the time in seconds it took to complete the last frame) returned by the following methods:

  • App::getIfps() returns the inverse FPS value for your application.
  • Game::getIfps() returns the scaled inverse FPS value. This class is to be used when you want to speed up, slow down or pause rendering, physics or game logic.
Notice
In order to be able to use the methods of the Game class or App class you must include UnigineGame.h or UnigineApp.h library correspondingly.

To scale your transformations you can use the following code:

Source code (C++)
// AppWorldLogic.cpp
#include <UnigineGame.h>

// injecting Unigine namespace to the global namespace
using namespace Unigine;

// global variable to store the inverse FPS value
float ifps;
	
/* .. */

int AppWorldLogic::update() {
	
	// getting an inverse FPS value (the time in seconds it took to complete the last frame)
	ifps = Game::get()->getIFps();
	
	// moving the node up by 0.3 units every second instead of every frame
	node->worldTranslate(Math::Vec3(0.0f, 0.0f, 0.3f*ifps));

	return 1;
}
/* .. */

To perform some changes once in a certain period of time you can use the following code:

Source code (C++)
#include <UnigineGame.h>

// injecting Unigine namespace to the global namespace
using namespace Unigine;
// AppWorldLogic.cpp

	const float INTERVAL_DURATION = 5;		// interval duration
	float ifps;								// global variable to store the inverse FPS value
	float elapsed_time = INTERVAL_DURATION;	// current time left to make changes
	
/* .. */

int AppWorldLogic::update() {
	
	// getting an inverse FPS value (the time in seconds it took to complete the last frame)
	ifps = Game::get()->getIFps();

	// checking if it's time to make changes
	if (elapsed_time < 0.0f)
	{
		
		/* .. DO SOME CHANGES .. */

		// resetting elapsed time counter
		elapsed_time = CHANGE_INTERVAL;
	}

	// decreasing elapsed time counter
	elapsed_time -= ifps;
	
	return 1;
}
/* .. */

Additional information:

  • For more information on the Game class, see Game class page.
  • For more information on the App class, see App class page.

Project Progress

In our project we are going to change the position of the sun and make some transformations to our initial set of objects every frame. As you already know, everything related to modification of nodes (moving, changing materials and parameters etc.) as well as other graphics-related functions to be called every frame should be placed in the AppWorldLogic::update() method. So, let us write metods called updateLights and updateObjects and place them to where they should be.

In the AppWorldLogic.h file, we define the duration of the time interval after which we are going to change the scale and direction of the forward vector for our objects, an auxiliary variable for the update cycle called elapsed_time and declare our updateLights and updateObjects methods.

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

const float CHANGE_INTERVAL = 1;		// the interval between changes of objects' parameters, in seconds
const float SUN_ROTATION_RATE = 10.0f;	// rotation rate of the sun

/* .. */

class AppWorldLogic : public Unigine::WorldLogic {
	
public:

/* .. */

private:

/* .. */

	// updating lights
	int updateLights();

	// updating objects
	int updateObjects();

/* .. */

	float elapsed_time = CHANGE_INTERVAL;	// current time left to change current scale of our objects
	float sun_angle = 0.0f;					// current sun position
/* .. */


};

In the AppWorldLogic.cpp file let us implement our updateObjects and updateLights methods and insert them into the AppWorldLogic::update() method. In the updateObjects method we are going to use the method from the previous section called transformNode. There is one more thing we should do: to initialize pseudo-random number generator in the AppWorldLogic::init() method.

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

// auxiliary variable to store the time of rendering the last frame
float ifps;

/* .. */

/// method updating positions of lights
int AppWorldLogic::updateLights()
{
	// updating the Sun rotation angle
	sun_angle += SUN_ROTATION_RATE * ifps;
	if (sun_angle > 360.0f) sun_angle = 0.0f;

	// changing the Sun position using the new angle
	LightWorld::cast(editor->getNodeByName("Sun"))->setWorldRotation(Math::quat(Math::vec3(0.0f, 1.0f, 0.0f), 180.0f - sun_angle));
	
	return 1;
}

/// method updating the initial set of scene objects
int AppWorldLogic::updateObjects()
{
	ObjectMeshDynamicPtr obj;

	// changing transformation for all scene objects named "my_meshdynamic_*" (initial set)
	for (auto it = Objects.begin(); it != Objects.end(); it++)
	{
		obj = it.get(); 
		if (strstr(obj->getName(), "my_meshdynamic_"))
		{
			// transform the node
			transformNode(obj->getNode());
		}
	}

	return 1;
}

/* .. */

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

	// initializing pseudo-random number generator
	Game::get()->setSeed(time(NULL));
	
/* .. */
}

/* .. */

int AppWorldLogic::update() 
{
	// getting an inverse FPS value (the time in seconds it took to complete the last frame)
	ifps = Game::get()->getIFps();

	// checking if it's time to change current scale and forward vector direction of our objects
	if (elapsed_time < 0.0f)
	{
		// change current scaling vector for objects
		current_objects_scale = Math::vec3(Game::get()->getRandomFloat(0.8f, 1.2f));
		
		// change forward direction for objects
		forward_direction = forward_direction * Math::rotateZ(60.0f);

		// resetting elapsed time counter
		elapsed_time = CHANGE_INTERVAL;
	}

	// decreasing the time counter to the next change of current scale and forward vector direction
	elapsed_time -= ifps;
	
	// updating objects
	updateObjects();

	// updating lights
	updateLights();

	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>
#include <UnigineEditor.h>
#include <UnigineGame.h>
#include <UnigineLights.h>
#include <UnigineMaterials.h>

// auxiliary constants
const float DELTA_ANGLE = 60.0f;		// delta angle of objects rotation
const float MOVING_SPEED = 3.0f;		// speed of objects movement
const float CHANGE_INTERVAL = 1.0f;		// the interval between changes of objects' parameters, in seconds
const float SUN_ROTATION_RATE = 10.0f;	// rotation rate of the sun

class AppWorldLogic : public Unigine::WorldLogic {
	
public:
	AppWorldLogic();
	virtual ~AppWorldLogic();
	
	virtual int init();
	
	virtual int update();
	virtual int render();
	virtual int flush();
	
	virtual int shutdown();
	virtual int destroy();
	
	virtual int save(const Unigine::StreamPtr &stream);
	virtual int restore(const Unigine::StreamPtr &stream);
private:
	Unigine::Editor *editor;
	Unigine::Materials *materials;
	Unigine::PlayerSpectatorPtr player;
	
	// pointers to light sources
	Unigine::LightWorldPtr thesun;
	Unigine::LightOmniPtr light_omni;
	Unigine::LightProjPtr projector;

	// auxiliary functions
	int addMeshToScene(const char *file_name, const char *mesh_name, const char *material_name, Unigine::Math::Vec3 position);
	int removeMeshFromScene(const char *node_name);
	int transformNode(Unigine::NodePtr node, float ifps);

	// initialization functions
	int initObjects();
	int initPlayer();
	int initLights();
	int initMaterials();

	// update functions
	int updateLights();
	int updateObjects();

	// shutdown functions
	int clearMaterials();
	int removeObjects();

	// scene objects vector
	Unigine::Vector <Unigine::ObjectMeshDynamicPtr> Objects;
	
	
	Unigine::Math::vec3 current_objects_scale = Unigine::Math::vec3(1.0f);			// current scaling vector for objects
	Unigine::Math::Vec3 forward_direction = Unigine::Math::Vec3(0.0f, -1.0f, 0.0f);	// current forward direction vector for objects
	float elapsed_time = CHANGE_INTERVAL;							// current time left to change current scale and forward direction of our objects
	float sun_angle = 0.0f;											// current sun position
};

#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.
using namespace Unigine;
// auxiliary variable to store the time of rendering the last frame
float ifps;

//-----------------------------------------------------------------------------------------------------------------------------
//---------------------------------------------- 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);
	
	// passing node ownership to the editor as a runtime node
	omd->release();
	editor->addNode(omd->getNode());

	// 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 deleting a Dynamic Mesh Object with a given name from the scene
int AppWorldLogic::removeMeshFromScene(const char *node_name)
{
	// getting a pointer to the node with a given name and downcasting it to ObjectMeshDynamicPtr
	ObjectMeshDynamicPtr object = ObjectMeshDynamic::cast(editor->getNodeByName(node_name));

	if (object)
	{
		// reporting node deletion to the console
		Log::message("Removing %s node named %s from the scene.\n", object->getTypeName(), node_name);

		// removing the node with a given name from the list of scene objects

		for (int i = 0; i < Objects.size(); i++)
		{
			if (strcmp(Objects[i]->getName(), node_name) == 0) {
				Objects.remove(i);
				break;
			}
		}

		// removing the node from the scene using upcasting
		editor->removeNode(object->getNode());

		return 1;
	}

	return 0;
}
//-----------------------------------------------------------------------------------------------------------------------------
/// method performing node transformations 
int AppWorldLogic::transformNode(NodePtr node, float ifps)
{
	// getting current node transformation matrix
	Math::Mat4 transform = node->getTransform();

	// calculating delta rotation around an arbitrary axis
	Math::quat delta_rotation = Math::quat(rand() % 2, rand() % 2, rand() % 2, DELTA_ANGLE * ifps);

	// setting node's scale, rotation and position
	node->setWorldScale(current_objects_scale);
	node->setWorldRotation(node->getWorldRotation() * delta_rotation);
	node->setWorldPosition(node->getWorldPosition() + forward_direction * MOVING_SPEED *ifps);

	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).get(), String::format("my_mesh_base%d", index).get(), Math::Vec3(x, y, 1.0f));
			index++;
		}
	}

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

	return 1;
}
//-----------------------------------------------------------------------------------------------------------------------------
/// method performing initialization of the player
int AppWorldLogic::initPlayer()
{
	// creating a new PlayerSpectator instance
	player = PlayerSpectator::create();

	// setting player's FOV, ZNear, ZFar
	player->setFov(90.0f);
	player->setZNear(0.1f);
	player->setZFar(10000.0f);

	// setting player's view direction vector and position
	player->setPosition(Math::Vec3(3.0f));
	player->setDirection(Math::vec3(-1.0f), Math::vec3(0.0f, 0.0f, -1.0f));

	// setting the player to the Game singleton instance
	Game::get()->setPlayer(player->getPlayer());
	player->release();

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

	return 1;
}
//-----------------------------------------------------------------------------------------------------------------------------
/// method performing initialization of lights
int AppWorldLogic::initLights()
{
	// creating an omni light and setting up its parameters
	light_omni = LightOmni::create(Math::vec4(1.0f, 1.0f, 1.0f, 1.0f), 10.0f, "");
	light_omni->setWorldPosition(Math::Vec3(0.0f, 0.0f, 5.0f));
	light_omni->setIntensity(0.1f);

	// passing node ownership to the editor
	light_omni->release();
	editor->addNode(light_omni->getNode());

	// reporting progress to the console
	Log::message("-> Created a %s light source.\n", light_omni->getName());

	// creating a world light and setting up its parameters
	thesun = LightWorld::create(Math::vec4(1.0f, 1.0f, 1.0f, 1.0f));
	thesun->setName("Sun");
	thesun->setDisableAngle(90.0f);
	thesun->setIntensity(1.0f);
	thesun->setScattering(LightWorld::SCATTERING_SUN);
	thesun->setWorldRotation(Math::quat(0.0f, 1.0f, 0.0f, 170.0f));

	// passing node ownership to the editor
	thesun->release();
	editor->addNode(thesun->getNode());

	// reporting progress to the console
	Log::message("-> Created a %s light source.\n", thesun->getName());

	// creating a proj light and setting up its parameters
	projector = LightProj::create(Math::vec4(1.0f, 1.0f, 0.5f, 1.0f), 10.0f, 60.0f, "");
	projector->setWorldPosition(Math::Vec3(2.5f, 2.5f, 3.0f));
	projector->setName("projector");
	projector->setRotation(Math::quat(-45.0f, 45.0f, 0.0f));
	projector->setPenumbra(0.425f);
	projector->setIntensity(1.0f);

	// passing node ownership to the editor
	projector->release();
	editor->addNode(projector->getNode());

	// reporting progress to the console
	Log::message("-> Created a %s light source.\n", projector->getName());
	Log::warning("Lights initialization OK!\n");

	return 1;
}
//-----------------------------------------------------------------------------------------------------------------------------
/// method performing initialization of materials
int AppWorldLogic::initMaterials()
{
	// getting a pointer to materials interface
	materials = Materials::get();

	// creating a new child material of the mesh_base and setting its color
	MaterialPtr mesh_base = materials->findMaterial("mesh_base");
	MaterialPtr my_mesh_base = mesh_base->inherit("my_mesh_base0");
	my_mesh_base->setParameter(Material::PARAMETER_COLOR, Math::vec4(255, 0, 0, 255));

	// reporting progress to the console
	Log::message("\n-> Generated %s material.\n", my_mesh_base->getName());

	// creating a new child material of the mesh_base and setting its color
	my_mesh_base = mesh_base->inherit("my_mesh_base1");
	my_mesh_base->setParameter(Material::PARAMETER_COLOR, Math::vec4(0, 255, 0, 255));

	// reporting progress to the console
	Log::message("-> Generated %s material.\n", my_mesh_base->getName());

	//creating a new child material of the mesh_base and setting its color
	my_mesh_base = mesh_base->inherit("my_mesh_base2");
	my_mesh_base->setParameter(Material::PARAMETER_COLOR, Math::vec4(0, 0, 255, 255));

	// reporting progress to the console
	Log::message("-> Generated %s material.\n", my_mesh_base->getName());

	//creating a new child material of the mesh_base and setting its color
	my_mesh_base = mesh_base->inherit("my_mesh_base3");
	my_mesh_base->setParameter(Material::PARAMETER_COLOR, Math::vec4(255, 255, 0, 255));

	// reporting progress to the console
	Log::message("-> Generated %s material.\n", my_mesh_base->getName());
	Log::warning("Material generation OK!\n\n");

	// clearing material pointer
	my_mesh_base.clear();

	return 1;
}
//-----------------------------------------------------------------------------------------------------------------------------
//---------------------------------------------------- UPDATE METHODS ---------------------------------------------------------
//-----------------------------------------------------------------------------------------------------------------------------
/// method updating the position of the sun
int AppWorldLogic::updateLights()
{
	// updating the Sun rotation angle
	sun_angle += SUN_ROTATION_RATE * ifps;
	if (sun_angle > 360.0f) sun_angle = 0.0f;

	// changing the Sun position using the new angle
	LightWorld::cast(editor->getNodeByName("Sun"))->setWorldRotation(Math::quat(Math::vec3(0.0f, 1.0f, 0.0f), 180.0f - sun_angle));

	return 1;
}
//-----------------------------------------------------------------------------------------------------------------------------
/// method updating the initial set of scene objects
int AppWorldLogic::updateObjects()
{
	ObjectMeshDynamicPtr object;

	// changing transformation for all scene objects named "my_meshdynamic_*" (initial set)
	for (auto it = Objects.begin(); it != Objects.end(); it++)
	{
		object = it.get();
		if (strstr(object->getName(), "my_meshdynamic_"))
		{
			// transform the node
			transformNode(object->getNode(), ifps);
		}
	}

	return 1;
}
//-----------------------------------------------------------------------------------------------------------------------------
//---------------------------------------------------- SHUTDOWN METHODS -------------------------------------------------------
//-----------------------------------------------------------------------------------------------------------------------------
/// method removing all created materials
int AppWorldLogic::clearMaterials()
{
	materials->removeMaterial(materials->findMaterial("my_mesh_base0")->getGUID());
	materials->removeMaterial(materials->findMaterial("my_mesh_base1")->getGUID());
	materials->removeMaterial(materials->findMaterial("my_mesh_base2")->getGUID());
	materials->removeMaterial(materials->findMaterial("my_mesh_base3")->getGUID());

	return 1;
}
//-----------------------------------------------------------------------------------------------------------------------------
/// method removing all  created objects
int AppWorldLogic::removeObjects()
{
	while (Objects.size() > 0)
	{
		removeMeshFromScene(Objects.begin()->get()->getName());
	}

	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.

	// initializing pseudo-random number generator
	Game::get()->setSeed(time(NULL));

	// getting a pointer to the Editor
	editor = Editor::get();

	// creating materials
	initMaterials();

	// creating objects
	initObjects();

	// creating a player
	initPlayer();

	// creating lights
	initLights();
	
	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.

	// getting an inverse FPS value (the time in seconds it took to complete the last frame)
	ifps = Game::get()->getIFps();

	// checking if it's time to change current scale and forward vector direction of our objects
	if (elapsed_time < 0.0f)
	{
		// change current scaling vector for objects
		current_objects_scale = Math::vec3(Game::get()->getRandomFloat(0.8f, 1.2f));

		// change forward direction for objects
		forward_direction = forward_direction * Math::rotateZ(60.0f);

		// resetting elapsed time counter
		elapsed_time = CHANGE_INTERVAL;
	}
	
	// decreasing the time counter to the next change of current scale and forward vector direction
	elapsed_time -= ifps;

	// updating objects
	updateObjects();

	// updating lights
	updateLights();

	return 1;
}

int AppWorldLogic::render() {
	// 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::flush() {
	// Write here code to be called before updating each physics frame: control physics in your application and put non-rendering calculations.
	// The engine calls flush() 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() {
// Write here code to be called on world shutdown: delete resources that were created during world script execution to avoid memory leaks.
		
	// deleting all created nodes
	removeObjects();

	// clearing the player pointer
	player.clear();

	// clearing light sources
	thesun.clear();
	light_omni.clear();
	projector.clear();

	// clearing all created materials
	clearMaterials();

	return 1;
}

int AppWorldLogic::destroy() {
	// Write here code to be called when the video mode is changed or the application is restarted (i.e. video_restart is called). It is used to reinitialize the graphics context.
	
	return 1;
}

int AppWorldLogic::save(const Unigine::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 Unigine::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: 2017-12-21