Voxel Chunk not rendering proper blocks?

Question

I am currently trying to learn about 3D, and am trying to have some fun with 3d arrays and all that fun stuff, while at it. I cannot seem to understand why my code is not rendering proper cubes... I run through a 3D array and assign random states (1 draw, 2 don't draw) I can't figure out why when I run through the states it only seems to draw all of the cubes or none.

any help is appreciated, excuse the bad code.

EDIT: (I added a cout file and fixed up a bit of code)

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <windows.h>
#include <time.h>


#include <SDL.h>
#include <GL/gl.h>
#include <GL/glu.h>
using namespace std;


float SCALE = 2;
int i;
int chunk[16][16][16];
int chunkSize = 16;
time_t seconds;
int seed = 0;
int colors;

void buildChunk();
void renderChunk();

void drawCube(float size,int x,int y,int z)
{


    glBegin(GL_QUADS);

    // front face
    glColor3f(0,200,255);
    glVertex3f(size/2*x,size/2+y,size/2+z);
    glVertex3f(-size/2*x,size/2+y,size/2+z);
    glVertex3f(-size/2*x,-size/2+y,size/2+z);
    glVertex3f(size/2*x,-size/2+y,size/2+z);
    // left face
    glColor3f(0.0,1.0,0.0);
    glVertex3f(-size/2*x,size/2+y,size/2+z);
    glVertex3f(-size/2*x,-size/2+y,size/2+z);
    glVertex3f(-size/2*x,-size/2+y,-size/2+z);
    glVertex3f(-size/2*x,size/2+y,-size/2+z);
    // back face
    glColor3f(0.0,0.0,1.0);
    glVertex3f(size/2*x,size/2+y,-size/2+z);
    glVertex3f(-size/2*x,size/2+y,-size/2+z);
    glVertex3f(-size/2*x,-size/2+y,-size/2+z);
    glVertex3f(size/2*x,-size/2+y,-size/2+z);
    // right face
    glColor3f(1.0,1.0,0.0);
    glVertex3f(size/2*x,size/2+y,size/2+z);
    glVertex3f(size/2*x,-size/2+y,size/2+z);
    glVertex3f(size/2*x,-size/2+y,-size/2+z);
    glVertex3f(size/2*x,size/2+y,-size/2+z);
    // top face
    glColor3f(1.0,0.0,1.0);
    glVertex3f(size/2*x,size/2+y,size/2+z);
    glVertex3f(-size/2*x,size/2+y,size/2+z);
    glVertex3f(-size/2*x,size/2+y,-size/2+z);
    glVertex3f(size/2*x,size/2+y,-size/2+z);
    // bottom face
    glColor3f(0.0,1.0,1.0);
    glVertex3f(size/2*x,-size/2+y,size/2+z);
    glVertex3f(-size/2*x,-size/2+y,size/2+z);
    glVertex3f(-size/2*x,-size/2+y,-size/2+z);
    glVertex3f(size/2*x,-size/2+y,-size/2+z);
    glEnd();
}

float angle = 0.0;
const int triangle = 1;

void init()
{

    glClearColor(0.0,0.0,0.0,1.0);  //background color and alpha
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45,640.0/480.0,1.0,500.0);
    glMatrixMode(GL_MODELVIEW);
    glEnable(GL_DEPTH_TEST);
    buildChunk();
}

void render()
{

    renderChunk();
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(0.0,0.0,-30.0);
    glRotatef(angle,1.0,1.0,0.0);   // angle, x-axis, y-axis, z-axis
}

int main(int argc, char** argv)
{
    SDL_Init(SDL_INIT_EVERYTHING);
    SDL_Surface *screen;
    screen = SDL_SetVideoMode(640, 480, 8, SDL_SWSURFACE|SDL_OPENGL);
//     screen = SDL_SetVideoMode(640, 480, 8, SDL_SWSURFACE|SDL_FULLSCREEN);
    bool running = true;
    const int FPS = 30;
    Uint32 start;
    SDL_Event event;
    init();
    while(running)
    {
        start = SDL_GetTicks();
        while(SDL_PollEvent(&event))
        {
            switch(event.type)
            {
            case SDL_QUIT:
                running = false;
                break;
            }
        }

        render();
        SDL_GL_SwapBuffers();
        angle += 0.5;
        if(angle > 360)
            angle -= 360;
        if(1000/FPS > SDL_GetTicks()-start)
            SDL_Delay(1000/FPS-(SDL_GetTicks()-start));
    }
    SDL_Quit();
    return 0;
}

void buildChunk()
{
    seconds = time (NULL);
    seed = seconds;
    srand(seed);
    /* Seed the random number generator with the specified seed */
    int x;
    int y;
    int z;



    for(x=0; x < chunkSize; x++)
    {
        for(y=0; y < chunkSize; y++)
        {
            for(z=0; z < chunkSize; z++)
            {




                /* 50% chance for a cell to be alive */
                if(rand() % 100 < 50)
                {
                    chunk[x][y][z] = 1;
                }
                else
                {
                    chunk[x][y][z] = 0;
                }
                cout<< "chunk[" << x << "][" << y << "][" << z << "]  state: " << chunk[x][y][z]<<endl;

            }
        }
    }
}

void renderChunk()
{
    int x;
    int y;
    int z;

    for(x=0; x < chunkSize; x++)
    {
        for(y=0; y < chunkSize; y++)
        {
            for(z=0; z < chunkSize; z++)
            {

                if(chunk[x][y][z] == 1)
                {
                    drawCube(1,x,y,z);
                }


            }
        }
    }
}

Answer 1

Notice that you have a '*' symbol in the first column of all of your glVertex3f calls. This should be a '+' to offset the vertex by x rather than scale it. You might also want to consider scaling the size of each cube by the size. You'll end up with something like:

    float halfSize = size / 2;
    float xSize = x * size;
    float ySize = y * size;
    float zSize = z * size;

    // front face
    glColor3f(0,200,255);
    glVertex3f(xsize + halfSize, ysize + halfSize, zsize + halfSize);
    glVertex3f(xsize - halfSize, ysize + halfSize, zsize + halfSize);
    glVertex3f(xsize - halfSize, ysize - halfSize, zsize + halfSize);
    glVertex3f(xsize + halfSize, ysize - halfSize, zsize + halfSize);