Question

I am creating a noob version clone of Minecraft. To begin with, i wanted to render a cube and add a specific texture to all sides to start. I have created a Block class that contains the vertices from input and has an output Function named RenderBlock to render the “Block” with the attached Texture.

Here is the Function that inputs 8 arrays representing 8 coordinates for the 8 vertices of the Block.

void Block::SetVertices(float UL[],float UR[],float ZR[],float ZL[],float UL2[],float           UR2[],float ZR2[],float ZL2[])
{
  Front_Square[1][1]=UL[1];
  Front_Square[1][2]=UL[2];
  Front_Square[1][3]=UL[3];
  std::cout << "Front Top Left Coordinates" << std::endl;    
  std::cout << Front_Square[1][1] << ","<<Front_Square[1][2] << "," << Front_Square[1][3] << std::endl;
  Front_Square[2][1]=UR[1];
  Front_Square[2][2]=UR[2];
  Front_Square[2][3]=UR[3];
  std::cout << "Front Top Right Coordinates" << std::endl;    
  std::cout << Front_Square[2][1] << ","<<Front_Square[2][2] << "," << Front_Square[2][3] << std::endl;
  Front_Square[3][1]=ZR[1];
  Front_Square[3][2]=ZR[2];
  Front_Square[3][3]=ZR[3];
  std::cout << "Front Bottom Right Coordinates" << std::endl;    
  std::cout << Front_Square[3][1] << ","<<Front_Square[3][2] << "," << Front_Square[3][3] << std::endl;
  Front_Square[4][1]=ZL[1];
  Front_Square[4][2]=ZL[2];
  Front_Square[4][3]=ZL[3];
  std::cout << "Front Bottom Left Coordinates" << std::endl;    
  std::cout << Front_Square[4][1] << ","<<Front_Square[4][2] << "," << Front_Square[4][3] << std::endl;
  //--------------BACK SQUARE------------------------------------------------------------------------------------------------------------------------//  
  Back_Square[1][1]=UL2[1];
  Back_Square[1][2]=UL2[2];
  Back_Square[1][3]=UL2[3];

  Back_Square[2][1]=UR2[1];
  Back_Square[2][2]=UR2[2];
  Back_Square[2][3]=UR2[3];

  Back_Square[3][1]=ZR2[1];
  Back_Square[3][2]=ZR2[2];
  Back_Square[3][3]=ZR2[3];

  Back_Square[4][1]=ZL2[1];
  Back_Square[4][2]=ZL2[2];
  Back_Square[4][3]=ZL2[3]; 
};

And here is the Function the renders the Block.

void Block::RenderBlock(const char*SideTexture)
{
 glEnable(GL_TEXTURE_2D);
 Tex[1]=loadTexture(SideTexture); 
 glBindTexture(GL_TEXTURE_2D, Tex[1]);
 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);  
 glBegin(GL_QUADS);
glTexCoord2f(0.0f, 1.0f); glVertex3f(Front_Square[1][1],Front_Square[1][2],Front_Square[1][3]);//FTL
glTexCoord2f(1.0f, 1.0f); glVertex3f(Front_Square[2][1],Front_Square[2][2],Front_Square[2][3]);//FTR
glTexCoord2f(1.0f, 0.0f); glVertex3f(Front_Square[3][1],Front_Square[3][2],Front_Square[3][3]);//FBR
glTexCoord2f(0.0f, 0.0f); glVertex3f(Front_Square[4][1],Front_Square[4][2],Front_Square[4][3]);//FBL
     glEnd();

    glBindTexture(GL_TEXTURE_2D, Tex[1]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
     glBegin(GL_QUADS);
glTexCoord2f(0.0f, 1.0f); glVertex3f(Back_Square[1][1],Back_Square[1][2],Back_Square[1][3]);//BTL
glTexCoord2f(1.0f, 1.0f); glVertex3f(Back_Square[2][1],Back_Square[2][2],Back_Square[2][3]);//BTR
glTexCoord2f(1.0f, 0.0f); glVertex3f(Back_Square[3][1],Back_Square[3][2],Back_Square[3][3]);//BBR
glTexCoord2f(0.0f, 0.0f); glVertex3f(Back_Square[4][1],Back_Square[4][2],Back_Square[4][3]);//BBL
     glEnd();


    glBindTexture(GL_TEXTURE_2D, Tex[1]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
     glBegin(GL_QUADS);
glTexCoord2f(0.0f, 1.0f); glVertex3f(Back_Square[1][1],Back_Square[1][2],Back_Square[1][3]);//BTL
glTexCoord2f(1.0f, 1.0f); glVertex3f(Front_Square[1][1],Front_Square[1][2],Front_Square[1][3]);//FTL
glTexCoord2f(1.0f, 0.0f); glVertex3f(Front_Square[4][1],Front_Square[4][2],Front_Square[4][3]);//FBL
glTexCoord2f(0.0f, 0.0f); glVertex3f(Back_Square[4][1],Back_Square[4][2],Back_Square[4][3]);//BBL
     glEnd();

    glBindTexture(GL_TEXTURE_2D, Tex[1]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
     glBegin(GL_QUADS);
glTexCoord2f(0.0f, 1.0f); glVertex3f(Back_Square[2][1],Back_Square[2][2],Back_Square[2][3]);//BTR
glTexCoord2f(1.0f, 1.0f); glVertex3f(Front_Square[2][1],Front_Square[2][2],Front_Square[2][3]);//FTR
glTexCoord2f(1.0f, 0.0f); glVertex3f(Front_Square[3][1],Front_Square[3][2],Front_Square[3][3]);//FBR
glTexCoord2f(0.0f, 0.0f); glVertex3f(Back_Square[3][1],Back_Square[3][2],Back_Square[3][3]);//BBR
     glEnd();

     glBindTexture(GL_TEXTURE_2D, Tex[1]);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
     glBegin(GL_QUADS);
glTexCoord2f(0.0f, 1.0f); glVertex3f(Back_Square[4][1],Back_Square[4][2],Back_Square[4][3]);//BBL
glTexCoord2f(1.0f, 1.0f); glVertex3f(Back_Square[3][1],Back_Square[3][2],Back_Square[3][3]);//BBR
glTexCoord2f(1.0f, 0.0f); glVertex3f(Front_Square[3][1],Front_Square[3][2],Front_Square[3][3]);//FBR
glTexCoord2f(0.0f, 0.0f); glVertex3f(Front_Square[4][1],Front_Square[4][2],Front_Square[4][3]);//FBL
     glEnd();

    glBindTexture(GL_TEXTURE_2D, Tex[1]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
     glBegin(GL_QUADS);
glTexCoord2f(0.0f, 1.0f); glVertex3f(Back_Square[1][1],Back_Square[1][2],Back_Square[1][3]);//BTL
glTexCoord2f(1.0f, 1.0f); glVertex3f(Back_Square[2][1],Back_Square[2][2],Back_Square[2][3]);//BTR
glTexCoord2f(1.0f, 0.0f); glVertex3f(Front_Square[2][1],Front_Square[2][2],Front_Square[2][3]);//FTR
glTexCoord2f(0.0f, 0.0f); glVertex3f(Front_Square[1][1],Front_Square[1][2],Front_Square[1][3]);//FTL
     glEnd();
    glDisable(GL_TEXTURE_2D);
     };

2 arrays for Blocks Dirt and Grass
Dirt

float TL[] = {0.0f,-1.0f,1.0f,0.0f};
float TR[] = {0.0f,1.0f,1.0f,0.0f};
float BR[] = {0.0f,1.0f,-1.0f,0.0f};
float BL[] = {0.0f,-1.0f,-1.0f,0.0f};
float TL2[] = {0.0f,-1.0f,1.0f,-2.0f};
float TR2[] = {0.0f,1.0f,1.0f,-2.0f};
float BR2[] = {0.0f,1.0f,-1.0f,-2.0f};
float BL2[] = {0.0f,-1.0f,-1.0f,-2.0f}

Grass

float DTL[] = {0.0f,-1.0f,1.0f+Grass_XChan,0.0f};
float DTR[] = {0.0f,1.0f,1.0f+Grass_XChan,0.0f};
float DBR[] = {0.0f,1.0f,-1.0f+Grass_XChan,0.0f};
float DBL[] = {0.0f,-1.0f,-1.0f+Grass_XChan,0.0f};
float DTL2[] = {0.0f,-1.0f,1.0f+Grass_XChan,-2.0f};
float DTR2[] = {0.0f,1.0f,1.0f+Grass_XChan,-2.0f};
float DBR2[] = {0.0f,1.0f,-1.0f+Grass_XChan,-2.0f};
float DBL2[] = {0.0f,-1.0f,-1.0f+Grass_XChan,-2.0f};

Sorry for long Code. Here is Main.cpp if you want to see it.

#include <GL/glut.h>
#include <iostream>
#include <assert.h>
#include <fstream>
#include "block.h"
using namespace std;
float positionX = 0.0f;
float positionY = 0.0f;
float positionZ = -4.0f;
float angle = 0.0f;
float RotX=0.01f;
float RotY=0.0f;
float RotZ=0.0f;
float Grass_XChan=2.0f;
float Grass_ZChan=-2.0f;
bool Render = true;
Block Dirt;
Block Grass;
float TL[] = {0.0f,-1.0f,1.0f,0.0f};
float TR[] = {0.0f,1.0f,1.0f,0.0f};
float BR[] = {0.0f,1.0f,-1.0f,0.0f};
float BL[] = {0.0f,-1.0f,-1.0f,0.0f};
float TL2[] = {0.0f,-1.0f,1.0f,-2.0f};
float TR2[] = {0.0f,1.0f,1.0f,-2.0f};
float BR2[] = {0.0f,1.0f,-1.0f,-2.0f};
float BL2[] = {0.0f,-1.0f,-1.0f,-2.0f};

float DTL[] = {0.0f,-1.0f,1.0f+Grass_XChan,0.0f};
float DTR[] = {0.0f,1.0f,1.0f+Grass_XChan,0.0f};
float DBR[] = {0.0f,1.0f,-1.0f+Grass_XChan,0.0f};
float DBL[] = {0.0f,-1.0f,-1.0f+Grass_XChan,0.0f};
float DTL2[] = {0.0f,-1.0f,1.0f+Grass_XChan,-2.0f};
float DTR2[] = {0.0f,1.0f,1.0f+Grass_XChan,-2.0f};
float DBR2[] = {0.0f,1.0f,-1.0f+Grass_XChan,-2.0f};
float DBL2[] = {0.0f,-1.0f,-1.0f+Grass_XChan,-2.0f};
void display(void)
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glTranslatef(positionX, positionY, positionZ);
  glPushMatrix();
  glRotatef(angle,RotX,RotY,RotZ);
  Dirt.RenderBlock("C:/Users/Progr_Anim/Desktop/textures/DirtBottom.bmp");
  Grass.RenderBlock("C:/Users/Progr_Anim/Desktop/textures/GrassTop.bmp");

  glPopMatrix();
  glutSwapBuffers();
   }
  //-------------------------------------------------------------------------------------------------------------------------------------------
    void HandleResize(int w, int h) {
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0, (float)w / (float)h, 1.0, 200.0);
   }
   void Camera(unsigned char key,int x,int y)
   {
   switch(key)
 {
  case 'w':
       positionZ += 0.08f;
       break;
  case 's':
       positionZ -= 0.08f;
       break;
  case 'a':
       positionX += 0.08f;
       break;
  case 'd':
       positionX -= 0.08f;
       break;
  case 'c':
       if(angle>=360.0f)
       {
       angle=0.0f;                
       }
       angle+=5.0f;
       break;
  case '1':
       angle = 0.0f;
       RotX=1.0f;
       RotY=0.0f;
       RotZ=0.0f;
       break;
  case '2':
       angle = 0.0f;
       RotX=0.0f;
       RotY=1.0f;
       RotZ=0.0f;
       break;
  case '3':
       angle = 0.0f;
       RotX=0.0f;
       RotY=0.0f;
       RotZ=1.0f;
       break;
  case 'q':
       exit(0);
       break;
     }     
  }
 int main(int argc, char** argv)
 {
   Dirt.SetVertices(TL,TR,BR,BL,TL2,TR2,BR2,BL2);
   Grass.SetVertices(DTL,DTR,DBR,DBL,DTL2,DTR2,DBR2,DBL2);
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
   //Create Window
   glutInitWindowSize(640,480);
   glutCreateWindow("Love");
   glEnable(GL_DEPTH_TEST);
   glEnable(GL_COLOR_MATERIAL);
   glutDisplayFunc(display);
   glutReshapeFunc(HandleResize);
   glutKeyboardFunc(Camera);
   glutIdleFunc(display);
   glutMainLoop();
     return 0;
    }

Here is the video with the rotation cubes with the Grass block on Top and Dirt Block on the Bottom.
Link

Answer 1

I’m going to take a punt at an answer here, as I don’t think there’s quite enough information in the post.

The arrays in this code are being used as if the 0th element does not exist, and the definitions of arrays used have an extra zero at the front as padding.

However some arrays are not defined in the code here, and must be declared elsewhere, probably with a size. I’m going to guess at this size being wrong for a 1-indexed array.

i.e. back_square and front_square are probably declared something like:

float back_square[4][3];

rather than:

float back_square[5][4];

which is how they are being used.

The result will be undefined behaviour, which in this case is possibly the overwriting of a vertex, collapsing one corner of a cube.

Either way, I would strongly recommend not using arrays in this fashion, and getting used to things starting at zero.