(OpenGL) Trying to get object to chase the camera, but unsure how

[Aideux]

Hey there! So, I'm trying to get my "Ogro" object to chase the camera, but I am currently unsure as to how to accomplish this. Could someone please help me out with this? I don't need AI that can navigate around objects or anything, just so the "Ogro" kind of makes a beeline for the camera. I am pretty certain that I would be able to accomplish this in my main.cpp:

/*
TODO (Necessary):
	
TODO (After base game has been completed):
	Make Ogro that chases player throughout collection time, one hit kill
COMPLETED:
	Check to see if there has already been a collision between camera and tree. If so, points and tapped trees don't increment (Complete)
	Set up countdown to "season end" (Complete)
	Change point values/textures individually (Complete)
	Make it so that only the tree trunk changes textures, not the leaves (Complete)	
	When the player presses 'r', restart the game, only after timer has run out (Complete)
	Make 60 trees (Complete)
*/

#include "Font.h"
#include "ogro.h"
#include "Box.h"
#include "md2model.h"
#include "sstream"
#include "Camera.h"
#include "Time.h"
#include <vector>
using namespace std;

#include "vgl.h"
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtx/norm.hpp>
using namespace glm;
#define SPACEBAR_KEY 32
#define ESCAPE_KEY 033
#define e 101

Camera* camera;
Ogro* ogro;
//Box* boxes;
Font* font;
string fontText;
vector<GameObject*> gameObjects;
vector<Box * > boxes;
//vector<Box * > boxes;

int treesTapped = 0, points = 0;


float lastTime;
bool keyDown[255];
bool collided = false, alreadyCollided;
int counter = 0, minute = 60, tapsInInventory = 10, playerHealth = 1;
bool gameOver = false, kill = false, playerDead;

void timer(int value)
{
	glutPostRedisplay();
	glutTimerFunc(25, timer, 0);

	if (counter == 40)
	{
		counter = 0;
		minute--;
	}
	counter++;
	if (minute <= 0)
	{
		gameOver = true;
		minute = 0;
	}
}

void newGame()
{
	camera->setPosition(vec3(20.0f, .5f, 0.0f));
	minute = 60;
	counter = 0;
	treesTapped = 0;
	points = 0;
	gameOver = false;
	kill = false;
	playerDead = false;
	playerHealth = 1;
	((Ogro*)gameObjects[163])->setPosition(vec3(55, 0, 55));
	
	for (auto i = gameObjects.begin(); i != gameObjects.end(); ++i)
	{
		if ((*i)->getType() == ObjectType::BOX)
		{
			auto b = (Box*)*i;
			if (b->collided1 != false && b->trunk == true)
			{
				b->ChangeTextureBack();
				b->alreadyCollided = false;
			}
		}
	}
}

void closeApp()
{
	delete camera;
	delete font;
	for (auto it = gameObjects.begin(); it != gameObjects.end(); ++it)
	{
		delete (*it);
	}	
}

void CheckKeyboard()
{

	if (gameOver == false && playerDead == false)
	{
		if (keyDown['a'])
			camera->RotateLeft();
		if (keyDown['d'])
			camera->RotateRight();
		if (keyDown['w'])
			camera->MoveForward();
		if (keyDown['s'])
			camera->MoveBackWard();
		/*if (keyDown['e'])
		camera->StrafeRight();
		if (keyDown['q'])
		camera->StrafeLeft();*/
	}

	vec3 p = camera->getPosition();
	camera->Update();


	for (auto i = gameObjects.begin(); i != gameObjects.end(); ++i)
	{
		if ((*i)->getType() == ObjectType::BOX)
		{
			auto b = (Box*)*i;
			if (camera->getPosition().x >= (b->Position.x - b->getXBuffer()) && camera->getPosition().x <= (b->Position.x + b->getXBuffer()))
			{
				if (camera->getPosition().z >= (b->Position.z - b->getZBuffer()) && camera->getPosition().z <= (b->Position.z + b->getZBuffer()))		//change to Z axis and get camera position instead of radius
				{
					if (b->collided1 == false)		//Makes it so that boxes[0] does not have collision
					{
						collided = false;
					}
					else if (b->collided1 == true && b->trunk == true)
					{
						collided = true;
						if (b->alreadyCollided == false && keyDown['e'])
						{
							if (b->mapleLeaves == true)
							{
								treesTapped++;
								points += 500;
								b->ChangeTexture();
								b->alreadyCollided = true;
							}
							else
							{
								treesTapped++;
								points += 100;
								b->ChangeTexture();
								b->alreadyCollided = true;
							}
						}
					}
				}
			}
		}
	}
	for (int j = 0; j <= gameObjects.size() - 1; j++)
	{
		if (gameObjects[j]->getType() == ObjectType::OGRO)		//If object is equal to Orgro, check to see if colliding
		{
			float distance = glm::distance(((Ogro*)gameObjects[j])->getPosition(), camera->getPosition());
			float cr = camera->getRadius();
			float mr = ((Ogro*)gameObjects[j])->getRadius();
			float sum = mr + cr;
			if (distance <= sum)			//Camera and orgro have collided if distance is less than or equal to radius of 
			{								//camera plus radius of monster
				kill = true;
			}
		}
	}
	
	if (collided)
	{
		camera->position = p;
		camera->Update();
	}
	if (!kill)
	{
		((Ogro*)gameObjects[163])->model->setAnimation(Ogro::Animations[Ogro::RUN].AnimationFrame);
	}
	if (kill)
	{
		playerHealth--;
		((Ogro*)gameObjects[163])->model->setAnimation(Ogro::Animations[Ogro::JUMP].AnimationFrame);
		playerDead = true;
	}

	if (camera->position.x >= 60.0f)
	{
		camera->position.x = 60.0f;
	}
	if (camera->position.x <= -60.0f)
	{
		camera->position.x = -60.0f;
	}
	if (camera->position.z >= 60.0f)
	{
		camera->position.z = 60.0f;
	}
	if (camera->position.z <= -60.0f)
	{
		camera->position.z = -60.0f;
	}

	srand(time(NULL));

}

float getElapsedSeconds()
{
	float currentTime = float(GetTickCount()) / 1000.0f;
	float seconds = float(currentTime - lastTime);
	lastTime = currentTime;
	return seconds;
}

void keyboardUp(unsigned char key, int x, int y)
{
	keyDown[key] = false;
}

void mouseMovement(int x, int y)
{
	static bool warp = true;

	if (warp)
	{
		if (x>glutGet(GLUT_WINDOW_WIDTH) / 2)
			camera->RotateRight();
		else if (x<glutGet(GLUT_WINDOW_WIDTH) / 2)
			camera->RotateLeft();

		if (y>glutGet(GLUT_WINDOW_HEIGHT) / 2)
			camera->RotateUp();
		else if (y<glutGet(GLUT_WINDOW_HEIGHT) / 2)
			camera->RotateDown();

		glutWarpPointer(glutGet(GLUT_WINDOW_WIDTH) / 2, glutGet(GLUT_WINDOW_HEIGHT) / 2);
		warp = false;
	}
	else
		warp = true;
}

void mouseWheel(int button, int direction, int x, int y)
{

	if (button == 16)
		camera->ResetFOV();
	else if (direction > 0)
		camera->ZoomIn();
	else
		camera->ZoomOut();
}

void keyboardSpecialKeys(int key, int x, int y)
{
	float yaw;
	switch (key)
	{
	case GLUT_KEY_LEFT:
		yaw = ((Ogro*)gameObjects[1])->getYaw();
		yaw -= 5.0;
		((Ogro*)gameObjects[1])->setYaw(yaw);
		break;
	case GLUT_KEY_RIGHT:
		yaw = ((Ogro*)gameObjects[1])->getYaw();
		yaw += 5.0;
		((Ogro*)gameObjects[1])->setYaw(yaw);
		break;
	}
}

void keyboard(unsigned char key, int x, int y)
{
	keyDown[key] = true;
	switch (key)
	{
	case ESCAPE_KEY:
		exit(EXIT_SUCCESS);
		break;
	//case 'e':
		/*if (collided)			//TODO: differentiate between the trees
		{
			((Box*)gameObjects[1])->ChangeTexture();
			treesTapped++;
			points += 100;
		}
		break;*/
	case 'r':
		if (gameOver || playerDead)
		{
			newGame();
		}
	}
	
}

void display()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	CheckKeyboard();

	if (fontText.length() != 0)
		font->printText(fontText, 350, 550, 25);

	float dt = getElapsedSeconds();
	for (int i = 0; i <= gameObjects.size() - 1; i++)
	{
		switch (gameObjects[i]->getType())
		{
		case ObjectType::BOX:
			((Box*)gameObjects[i])->setMVPMatrix(camera->ViewMatrix, camera->ProjectionMatrix);
			gameObjects[i]->Draw(dt);
			break;
		case ObjectType::OGRO:
			((Ogro*)gameObjects[i])->changeInTime = dt;
			((Ogro*)gameObjects[i])->Draw(camera->ViewMatrix, camera->ProjectionMatrix);
			break;
		}
	}

	/*if (timer == 40)
	{
		timer = 0;
		seconds--;
	}
	timer++;*/

	std::stringstream ss1;
	ss1 << "Trees tapped: " << treesTapped;
	font->printText(ss1.str().c_str(), 20, 510, 15);
	std::stringstream ss2;
	ss2 << "Points: " << points;
	font->printText(ss2.str().c_str(), 20, 480, 15);
	std::stringstream ss3;
	ss3 << "Time until season end: " << minute;
	font->printText(ss3.str().c_str(), 143, 570, 20);
	
	if (gameOver)
	{
		std::stringstream ss4;
		ss4 << "Nice haul!";
		font->printText(ss4.str().c_str(), 270, 330, 25);
		std::stringstream ss5;
		ss5 << "Press 'r' to play again!";
		font->printText(ss5.str().c_str(), 100, 310, 25);
	}
	if (playerDead)
	{
		std::stringstream ss4;
		ss4 << "You got caught!";
		font->printText(ss4.str().c_str(), 270, 330, 25);
		std::stringstream ss5;
		ss5 << "Press 'r' to play again!";
		font->printText(ss5.str().c_str(), 100, 310, 25);
	}
	glutSwapBuffers();
}


void init()
{
	glClearColor(0.0f, 0.0f, 0.7f, 0.0f);
	glEnable(GL_DEPTH_TEST);
	glDepthFunc(GL_LESS);

	
	font = new Font();
	camera = new Camera();
	camera->setPosition(vec3(20.0f, .5f, 0.0f));
	glutWarpPointer(glutGet(GLUT_WINDOW_WIDTH) / 2, glutGet(GLUT_WINDOW_HEIGHT) / 2);
	std::fill(keyDown, keyDown + 255, false);
							
																																											//bools: vsibility, collided1, already collided, trunk, mapleLeaves
	gameObjects.push_back(new Box(vec3(0.0f, -2.0f, 0.0f), "data/images/grass-1.png", "data/shaders/Texture.vertexshader", "data/shaders/Texture.fragmentshader", "Data\\Models\\Floor.xml", true, 0.1f, vec3(70.0f, 0.1f, 70.0f), true, false, true, false, false));
	//New tree (trunk+leaves)
	gameObjects.push_back(new Box(vec3(0.0f, -2.0f, 0.0f), "data/images/wood.bmp", "data/shaders/Texture.vertexshader", "data/shaders/Texture.fragmentshader", "Data\\Models\\Floor.xml", true, 0.1f, vec3(1.0f, 10.0f, 1.0f), true, true, false, true, false));
	gameObjects.push_back(new Box(vec3(0.0f, 6.0f, 0.0f), "data/images/leaves.jpg", "data/shaders/Texture.vertexshader", "data/shaders/Texture.fragmentshader", "Data\\Models\\Floor.xml", true, 0.1f, vec3(2.5f, 2.5f, 2.5f), true, true, false, false, false));
	//New tree (trunk+leaves)

//JUST IMAGINE 160 OTHER TREE OBJECTS HERE
//I REMOVED FOR THE SAKE OF READABILITY

	gameObjects.push_back(new Ogro());
	((Ogro*)gameObjects[163])->Initialize();
	((Ogro*)gameObjects[163])->setPosition(vec3(-55, 0, -55));
	((Ogro*)gameObjects[163])->setDirection(vec3(1, 0, 0));
	((Ogro*)gameObjects[163])->setYaw(90);

	/*gameObjects.push_back(new Ogro());
	((Ogro*)gameObjects[2])->Initialize();
	((Ogro*)gameObjects[2])->setYaw(-90);
	((Ogro*)gameObjects[2])->setPosition(vec3(0, 0, -3));
	((Ogro*)gameObjects[2])->setDirection(vec3(1, 0, 0));*/
}



int main(int argc, char** argv)
{
	glutInit(&argc, argv);

	glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH);
	glutInitWindowSize(1024, 768);
	glutInitContextProfile(GLUT_CORE_PROFILE);
	glutCreateWindow("Model Example1");
	

	if (glewInit())
	{
		cerr << "Unable to init glew" << endl;
		exit(EXIT_FAILURE);
	}

	init();
	glutDisplayFunc(display);
	glutKeyboardFunc(keyboard);
	glutKeyboardUpFunc(keyboardUp);
	glutSpecialFunc(keyboardSpecialKeys);
	//glutPassiveMotionFunc(mouseMovement);
	glutMouseWheelFunc(mouseWheel);
	glutTimerFunc(25, timer, 0);
	glutMainLoop();
	return 0;
}

I know how to get both the positions of the camera and the ogro, but what to do after this is confusing me greatly. Thank you so much for all the help!

[2kaud]

TODO (After base game has been completed):
Make Ogro that chases player throughout collection time, one hit kill

but what to do after this is confusing me greatly

This is the problem with these types of exercises! After some part is working you are expected to then modify it to add further 'features'. Unless the design of the program from the start incorporates these 'features', it is not always easy to do! Although in the real programming world, this is quite common - so the experience is useful.

Rather than dive head in and start adding code, I would suggest you go back to the program design, change the design and then make the required code changes.

[Aideux]

This is the problem with these types of exercises! After some part is working you are expected to then modify it to add further 'features'. Unless the design of the program from the start incorporates these 'features', it is not always easy to do! Although in the real programming world, this is quite common - so the experience is useful.

Rather than dive head in and start adding code, I would suggest you go back to the program design, change the design and then make the required code changes.

I know my program is logically unsound and inefficient, but I really just need help with the math and logic of how I would get the model to chase the camera. I do agree that these exercises could be handled in a much more learning appropriate way, however, but it's due next week and I would much rather get the program working than worry about rewriting the whole thing.

I do really appreciate all the help you've provided me 2kaud. I really means a lot.