Trying to Make Endless Runner C++ with OpenGL - c++

Question

I have an array of cube objects initialised like so (index 0 not used here as that's for the player):
game_object[1] = new GameObject();
game_object[1]->setPosition(vec3(7.0f, 0.0f, 0.0f));
game_object[2] = new GameObject();
game_object[2]->setPosition(vec3(14.0f, 0.0f, 0.0f));
game_object[3] = new GameObject();
game_object[3]->setPosition(vec3(21.0f, 0.0f, 0.0f));
game_object[4] = new GameObject();
game_object[4]->setPosition(vec3(36.0f, 0.0f, 0.0f));
game_object[5] = new GameObject();
game_object[5]->setPosition(vec3(42.0f, 0.0f, 0.0f));
I have a render function in which they are drawn:
glDrawElements(GL_TRIANGLES, 3 * INDICES, GL_UNSIGNED_INT, NULL);
In my update they move to the left as expected. To do this I am just adding another vector to their positions:
for (int i = 1; i < MAX_CUBES; i++)
{
game_object[i]->setPosition(game_object[i]->getPosition() + vec3(-0.03, 0.0, 0.00));
}
However, I want the cubes to repeat this until the user exits the game. I made a reset function to send them back to their starting positions:
void Game::reset()
{
game_object[0]->setPosition(vec3(0.0f, 0.0f, 0.0f));
game_object[1]->setPosition(vec3(7.0f, 0.0f, 0.0f));
game_object[2]->setPosition(vec3(14.0f, 0.0f, 0.0f));
game_object[3]->setPosition(vec3(21.0f, 0.0f, 0.0f));
game_object[4]->setPosition(vec3(36.0f, 0.0f, 0.0f));
game_object[5]->setPosition(vec3(42.0f, 0.0f, 0.0f));
}
This function gets called in the update when the final cube's position is off screen to the left:
if (game_object[5]->getPosition().x <= 0.0)
{
reset();
}
However, this isn't working. Nothing resets after the last cube goes to the left.

Answer 1

Not sure how you are using game_object here but looks very error prone. If you have MAX_CUBES = 5 (as you do have 5 cubes), then that for-loop will miss the last one. Adding further objects (e.g. for gaps, vertical rules, hazards, etc.) will make it even more so.
for (int i = 1; i < MAX_CUBES; i++)
{
game_object[i]->setPosition(game_object[i]->getPosition() + vec3(-0.03, 0.0, 0.00));
}
If MAX_CUBES = 5, then it will move index 1, 2, 3, 4, and not 5, which is the one you check in the condition. 5 will just stay at 42 permanently (is that off-screen?).
Stepping through the code in a debugger will make a problem like this pretty clear regardless, and is an essential tool for programming. Maybe the code just never reaches the if (game_object[5]->getPosition().x <= 0.0) check in the first place? Is there any return in that update function, or is that condition inside another one of some sorts?

Answer 2

Because in your comment you noted that game_object[5]->getPosition().x returns a correct value, the most likely problem is with your reset() function and the setPosition function you are using.
1. Check if set position is working in the first place
Perhaps there is an error with setPosition().
After you set the position using setPosition() and then log the object's coordinates using getPosition() does it return the position you expect?
If not, something is wrong with setPosition.
If so, then...
2. You probably changed the position but failed to render it!
This is a very common problem lol
There is a very high chance you changed the position of the object BUT didn't update what's shown on the screen!
3. Side note for scalability
There is a much more efficient and scalable way of doing a reset if you have eventually have more than 5 objects, by placing their reset values in an array and looping through them:
#define MAX_CUBES 6
double resetPositions_x[MAX_CUBES] = {0.0, 7.0, 14.0, 21.0, 36.0, 42.0};
void Game::reset()
{
for(int i=0;i<MAX_CUBES;i++){
game_object[i]->setPosition(vec3(resetPositions_x[i], 0.0f, 0.0f));
}
}
(Also, it seems every x reset position is a multiple of 7 except 36.0 -> is that a mistake?)