Drawing an array of objects in Open GL Glut - c++

Question

I have been trying to draw multiple balls for a game I am making, I have tried to get this working but there are problems in my init class and display method class, I have commented it where the errors are.
Ball.h:
#pragma once
#include "Vector2f.h"
#include "Vector3f.h"
class Ball
{
private:
Vector3f position;
Vector3f velocity;
public:
Ball(void);
~Ball(void);
void Draw();
void SetPos(Vector3f New_position);
void SetVel(Vector3f New_velocity);
Vector3f GetPos();
};
Ball.cpp
#include "Ball.h"
#include "Vector2f.h"
#include "Vector3f.h"
#include "Glut/glut.h"
#include "GL/gl.h"
#include "GL/glu.h"
Ball::Ball(void)
{
Vector3f Temp_position;
position = Temp_position;
Vector3f Temp_velocity;
velocity = Temp_velocity;
}
Ball::~Ball(void)
{
}
void Ball::SetPos(Vector3f New_position)
{
position = New_position;
}
void Ball::Draw()
{
glPushMatrix();
glTranslatef(position.X(), position.Y(), position.Z());
glColor3d(1, 0, 0);
glutSolidSphere(0.3, 50, 50);
glPopMatrix();
}
void Ball::SetVel(Vector3f New_velocity)
{
velocity = New_velocity;
}
Vector3f Ball::GetPos()
{
Vector3f temp;
temp = position;
return temp;
}
I want the be able to draw an array of the balls in Main.cpp
Main.cpp
#include "Display.h"
#include "Vector3f.h"
#include "Ball.h"
#include "Glut/glut.h"
#include "GL/gl.h"
#include "GL/glu.h"
#include <math.h>
static float TableWidth = 4; // Z axis normal = 4
float Display::eyeX = -7.5; //-7.5
float Display::eyeY = 3; //3
float Display::eyeZ = 5; //5
float Display::Position[4] = { 1.0f, 0.0f, -3.5, 1.0f };
float Display::translateZ = -3.5;
float Display::translateX = 0.0;
//Timer Display::m_Timer = Timer();
float Display::lightX = 5.0; //5 2.5
float Display::lightY = 5.0;
float Display::lightZ = 2.5;
float m_TableX = -5.0f;
float m_TableZ = -2.5f;
float m_TableWidth = 2.5f;
float m_TableLength = 5.0f;
float ballx = 0.7;
float bally = 0.1;
float ballz = -0.7;
Ball Redball;
float BALL_RED_START = 0;
float RADIUS_OF_BALL = 0.3;
float BALL_RED_END = 8;
float m_ball;
void Display::Init(int argc, char ** argv)
{
glutInit(&argc, argv); // initializes glut
// sets display mode. These parameter set RGB colour model
// and double buffering.
glutInitWindowSize(500,500);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
glutCreateWindow("Pool Version 1.0");
// Set glut callback functions
glutDisplayFunc(Display::DisplayScene);
glutIdleFunc(Display::Idle);
glutReshapeFunc(Display::Resize);
glutKeyboardFunc(Display::KeyboardInput);
//m_Timer.getSeconds();
glEnable(GL_DEPTH_TEST);
glPointSize(5);
glEnable(GL_NORMALIZE);
glEnable(GL_LIGHTING);
glClearColor(0,0,0,1);
glEnable(GL_COLOR_MATERIAL);
float white[] = { 1.0f, 1.0f, 1.0f, 1.0f };
glLightfv(GL_LIGHT0, GL_DIFFUSE, white);
glEnable(GL_LIGHT0);
Redball.SetPos(Vector3f(0.0,0.3,0.0));
for(int i = BALL_RED_START; i < BALL_RED_START; i++)
{
glColor3f(1,0,0);
Redball[i]->SetPos(Vector3f (i+128,RADIUS_OF_BALL,45)); //I tried this but it doesn't work Error C2227
}
// Begin glut main loop
glutMainLoop();
}
void BallMovement()
{
//Vector3f position(0.0,0.3,0.0);
/*Redball.SetPos(Vector3f(0.0,0.3,0.0));*/
Vector3f New_velocity(0.01,0,0);
Redball.SetVel(New_velocity);
Vector3f New_position;
Vector3f Old_position;
Old_position = Redball.GetPos();
//New_position = Old_position + New_velocity;
New_position.SetX(Old_position.X() + New_velocity.X());
New_position.SetY(Old_position.Y() + New_velocity.Y());
New_position.SetZ(Old_position.Z() + New_velocity.Z());
Redball.SetPos(New_position);
}
void Display::DisplayScene()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear the back buffer
glPushMatrix();
glLoadIdentity();
glNormal3f(0,1,0);
Vector3f didums = Redball.GetPos();
gluLookAt(eyeX, eyeY, eyeZ, // eye position
0, 0, 0, // what I'm looking at
0.0, 1.0, 0); // Up direction
float Position[] = {lightX, lightY, lightZ, 1.0f};
glLightfv(GL_LIGHT0, GL_POSITION, Position);
DrawLight(0, Position);
/* Rendering code goes here */
for (int i = BALL_RED_START; i<BALL_RED_END;i++)
{
glColor3f(1,0,0);
Redball[i]->Draw(); //I tried this but it doesn't work Error C2227
}
drawTable();
drawTableLegFrontLeft();
drawTableLegFrontRight();
drawTableLegBackLeft();
drawTableLegBackRight();
drawCushions();
//drawCircle();
//drawHCircle();
Table(-2,-4.5,2,4.5); // Draws the table top in trianglestrip -4.5, 0.5, -0.5, 9.5
glPopMatrix();
glutSwapBuffers(); // Swap the front and back buffers
}
void Display::Resize(int w, int h)
{
/* Resize is called when window is resized */
glMatrixMode(GL_PROJECTION); // set matrix mode to profection
// this dictates how the 3d scene is "squashed" onto the 2d screen
glLoadIdentity();
glViewport(0, 0, w, h); // Set the part of the window to use.
gluPerspective(45, // field of view
(float)w/(float)h, // ration of window
1, // front clipping plane
1000 // back clipping plane
); // set the area in the 3d scene to draw
glMatrixMode(GL_MODELVIEW); // Setthe matrix mode to model view
// the matrix specifies how the 3d scene is viewed
/*glLoadIdentity();
gluLookAt(-3.5, 2, eyeZ, // eye position
1, 1, 0, // what I'm looking at
0.0, 1.0, 0); // Up direction*/
}
void Display::Idle()
{
/* When nothing else is happening, idle is called.
* Simulation should be done here and then
* the display method should be called
*/
BallMovement();
glutPostRedisplay();
}

Answer 1

I see you have declared Ball as Ball Redball; which will create a single Ball on the stack.
Then you attempt to treat it as a collection of Balls with Redball[i]->SetPos(...) and Redball[i]->Draw(). It appears you are attempting to work with 8 of them.
What you want to do is create an array of Balls, with a max size of 8 (according to BALL_RED_END). For simplicity, you could do
Ball RedBall[8];
for( //some conditions here )
{
RedBall[i].Draw();
}
as your declaration and usage.
Remember that anytime you use Redball.SetPos(...) will no longer be valid.