Question

I’ve came upon a problem regarding 2D textures placed on 2D quads. I have a space arcade game and it has asteroids,planets and a ship (with textures) that load perfectly fine.

I’m now working on power ups but for some weird reason it only shows one of the 3 different textures I designated on each power up and shows up a big version of the texture at the upper left cornor from time to time which doesn ‘t do anything (no collision function).

I’m loading the texture into the variables before entering the game loop and checked if it is actually loaded and the int values held values so that is fine. When an asteroid is destroyed a PowerUp Object is instantiated and the GLuint texture property is filled with the int value from the texture previously loaded.

I’ll post some code fragments to display some error I might be making:

//Initialisation of Vectors that hold all PowerUps dropped in game
vector<PowerUp_Speed> powerUps;
vector<PowerUp_Gun> powerUps_Gun;
vector<PowerUp_FireRate> powerUps_FireRate;

//PowerUps Texture Loading  (Before the main loop and after SDL init)
int speedTexture = loadTexture("sprites/Speed.png");
int rateTexture = loadTexture("sprites/Rate.png");
int gunTexture = loadTexture("sprites/Gun.png");

Following section is IN the main loop (when bullet vs asteroid collision occurs)

//PowerUps
PowerUp_Speed boost;
boost.texture = speedTexture;
bool push = boost.Drop(powerUps, destr[d]);
if(push)    powerUps.push_back(boost);

PowerUp_Gun gunBoost;
gunBoost.texture = rateTexture;
push = gunBoost.Drop(powerUps_Gun, destr[d]);
if(push)    powerUps_Gun.push_back(gunBoost);

PowerUp_FireRate fireBoost;
fireBoost.texture = gunTexture;
push = fireBoost.Drop(powerUps_FireRate, destr[d]);
if(push)    powerUps_FireRate.push_back(fireBoost);

And one of the PowerUp Objects to display how these function:

#include "SpaceGame.h"

PowerUp_Speed::PowerUp_Speed()
{
    isAlive = true;
    width = 40;
    height = width;
    chance = 5;
}

void PowerUp_Speed::boostPlayer(Ship &ship)
{
    ship.vel += 0.1f;
}

void PowerUp_Speed::Draw()
{
    if(isAlive)
    {
        glPushMatrix();
        glColor4ub(255, 255, 255, 255);
        glEnable(GL_TEXTURE_2D);
        glBindTexture(GL_TEXTURE_2D, texture);
        glBegin(GL_QUADS);
            glTexCoord2d(0,0); glVertex2f(x, y);
            glTexCoord2d(1,0); glVertex2f(x + width, y);
            glTexCoord2d(1,1); glVertex2f(x + width, y + height);
            glTexCoord2d(0,1); glVertex2f(x, y + height);
        glDisable(GL_TEXTURE_2D);
        glPopMatrix();
    }
}

bool PowerUp_Speed::Drop(vector<PowerUp_Speed> &powerUps, Destructable d)
{
    if(rand() % chance == 1)
    {
        if(powerUps.size() == 0)
        {
            x = d.x;
            y = d.y;
            return true;
        }
        else
        {
            bool succes = false;

            for(unsigned int i = 0; i < powerUps.size(); i++)
            {
                if(!powerUps[i].isAlive)
                {
                    powerUps[i].isAlive = true;
                    powerUps[i].x = d.x;
                    powerUps[i].x = d.y;
                    powerUps[i].texture = texture;
                    succes = true;
                    return false;
                }
            }

            if(!succes)
            {
                x = d.x;
                y = d.y;
                return true;
            }
        }
    }
    return false;
}

and its decleration in a header file:

class PowerUp_Speed
{
    public:
        float x, y;
        int width, height;
        int chance;
        bool isAlive;
        GLuint texture;
        PowerUp_Speed();
        void Draw();
        void boostPlayer(Ship &ship);
        bool Drop(vector<PowerUp_Speed> &powerUps, Destructable d);
};

Answer 1

Add a glEnd() to PowerUp_Speed::Draw():

glBegin(GL_QUADS);
    glTexCoord2d(0,0); glVertex2f(x, y);
    glTexCoord2d(1,0); glVertex2f(x + width, y);
    glTexCoord2d(1,1); glVertex2f(x + width, y + height);
    glTexCoord2d(0,1); glVertex2f(x, y + height);
glEnd();

Every glBegin() needs a corresponding glEnd().