OpenGL Linux Line Drawing Problem

This is a discussion on OpenGL Linux Line Drawing Problem within the C++ Programming forums, part of the General Programming Boards category; Hello; I am having a problem in openGL. I use the GLUT lib. I am trying to draw som lines ...

  1. #1
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    Sep 2005
    Posts
    85

    OpenGL Linux Line Drawing Problem

    Hello;

    I am having a problem in openGL. I use the GLUT lib. I am trying to draw som lines using glVertex3f(x,y,z). Once these lines are drawn, I wna to manipulate them with the glScalef(x,y,z)...glRotate(x,y,z) and so forth. I can get the image drawn, but no manipulation is happening, can someone please help.

    For the example, we can draw a cube using the glVertex3f command, and use that to be maipulated.

  2. #2
    #define WORLD "sad place" LinuxCoder's Avatar
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    Portugal
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    Once these lines are drawn, I wna to manipulate them with the glScalef(x,y,z)...glRotate(x,y,z) and so forth.
    These commands only affect matrixes, either the GL_PROJECTION matrix or the GL_MODELVIEW matrix according to which one is selected at the moment you call these, this means that only drawing commands after these calls will suffer the effect of these transforms. The correct way to achieve that is to have the calls to glRotate() and glScale() before the actual drawinng commands like glVertex3f() and such.

    Cheers

  3. #3
    Registered User
    Join Date
    Sep 2005
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    85
    Here is my full code
    Please Take a look: (it is a work in progress)

    Code:
    #include <GL/glut.h>
    #include <cstdlib>
    #include <iostream>
    #include <cmath>
    #include <time.h>
    #include <string>
    #include <vector>
    #include <fstream>
    
    using namespace std;
    
    struct coord
    {
      float x_c;
      float y_c;
      float z_c;
    };
    
    int x_1,y_1,x_2,y_2;
    float xspin,yspin;
    int button_down;
    bool key;
    float xrot, yrot, zrot;
    float xtrans, ytrans, ztrans;
    int colorChoice = 0;
    int shapeChoice = 0;
    float sizeChoice = 1;
    bool   moveOrder = false;
    bool   oldMoveOrder;
    vector <coord> cord;
    vector <vector <int> > verts;
    float scale_size;
    float orig_scale_size;
    bool wire_or_solid;
    bool cull_or_not;
    
    
    void find_scale()
    {}
    
    void draw_image()
    {
    
      //cout << "------------------------FUNCT CALLED-------------"<<endl;
      int a,b,c;
      float tmp_x,tmp_y,tmp_z;
      int from,to;
    
      for(a=0;a<verts.size();a++)
      {
        c = 0;
        for(b=0;b<verts.at(a).size()-1;b++)
        {
          from = verts.at(a).at(b);
          tmp_x = cord[from].x_c;
          tmp_y = cord[from].y_c;
          tmp_z = cord[from].z_c;
          glVertex3f(tmp_x,tmp_y,tmp_z);
          //cout << "From: " << tmp_x << " " << tmp_y << " " << tmp_z;
    
          to = verts.at(a).at(b+1);
          tmp_x = cord[to].x_c;
          tmp_y = cord[to].y_c;
          tmp_z = cord[to].z_c;
          glVertex3f(tmp_x,tmp_y,tmp_z);
          //cout << " TO " << tmp_x << " " << tmp_y << " " << tmp_z << endl;
    
        }
        from = verts.at(a).at(b);
        tmp_x = cord[from].x_c;
        tmp_y = cord[from].y_c;
        tmp_z = cord[from].z_c;
        glVertex3f(tmp_x,tmp_y,tmp_z);
        //cout << "From: " << tmp_x << " " << tmp_y << " " << tmp_z;
        b = 0;
        to = verts.at(a).at(b);
        to = verts.at(a).at(b+1);
        tmp_x = cord[to].x_c;
        tmp_y = cord[to].y_c;
        tmp_z = cord[to].z_c;
        glVertex3f(tmp_x,tmp_y,tmp_z);
        //cout << " TO " << tmp_x << " " << tmp_y << " " << tmp_z << endl;
    
        find_scale();
      }
    }
    void display()
    {
    
    
      glClear(GL_COLOR_BUFFER_BIT);
      glLoadIdentity();
    
      glPushMatrix();
      switch(wire_or_solid)
      {
      case true:glBegin(GL_LINES); break;
      case false:glBegin(GL_POLYGON); break;
      }
      switch(cull_or_not)
      {
      case true:glEnable(GL_CULL_FACE); break;
      case false:glDisable(GL_CULL_FACE) ;break;
      }
      
      
      if(moveOrder )
      {
        glTranslatef(xtrans, ytrans, ztrans);
      }
    
      glRotatef(xrot,1,0,0);
      glRotatef(yrot,0,1,0);
      glRotatef(zrot,0,0,1);
    
      if(!moveOrder)
      {
        glTranslatef(xtrans, ytrans, ztrans);
      }
    
      glScalef(scale_size, scale_size, scale_size);
    
      switch(colorChoice)
      {
      case 0: glColor3f(1,0,0); break;
      case 1: glColor3f(0,1,0); break;
      case 2: glColor3f(0,0,1); break;
      }
    
    
      //DrawShapeHere
      draw_image();
    
      
      glPopMatrix();
      glEnd();
      glutSwapBuffers();
    }
    
    void initMoves()
    {
      xrot=0;
      yrot=0;
      zrot=0;
      xspin = 0;
      yspin = 0;
      xtrans = 0;
      ytrans = 0;
      ztrans = 0;
    }
    
    void show_keys()
    {
    
      cout << "-----IN ROTATON MODE----" << endl;
      cout << "q: exit" << endl;
      cout << "x: xrot += 5" << endl;
      cout << "y: yrot += 5" << endl;
      cout << "z: zrot += 5" << endl;
      cout << "X: xrot -= 5" << endl;
      cout << "Y: yrot -= 5" << endl;
      cout << "Z: zrot -= 5" << endl;
      cout << "r: reset" << endl << endl;
      cout << "-----IN ROTATON MODE----" << endl;
      cout << "q: exit" << endl;
      cout << "x: xtrans += .05" << endl;
      cout << "y: ytrans += .05" << endl;
      cout << "z: ztrans += .05" << endl;
      cout << "X: xtrans -= .05" << endl;
      cout << "Y: ytrans -= .05" << endl;
      cout << "Z: ztrans -= .05" << endl;
      cout << "r: reset" << endl << endl;
      cout << "-----MOUSE BUTTONS----" << endl;
      cout << "left button  : menu" << endl;
      cout << "middle button: rotate" << endl;
      cout << "right button : translate" << endl;
    
    
    }
    
    void myinit()
    {
      initMoves();
      x_1 = 0;
      x_2 = 0;
      y_1 = 0;
      y_2 = 0;
      xspin = 0;
      yspin = 0;
      key = false;
      float scale_size = 1.0;
      bool wire_or_solid = true;
      bool cull_or_not = true;
    
    
      glMatrixMode(GL_PROJECTION);
      glLoadIdentity();
      glOrtho(-2.0,2.0,-2.0,2.0,-2.0,2.0);
      glMatrixMode(GL_MODELVIEW);
      glClearColor(1.0,1.0,1.0,1.0);
      glColor3f(0.0,0.0,0.0);
    
    }
    
    void fileReady()
    {
      vector <int> temp_verts;
      string line;
      int num_lines;
      int i;
      int x1c,y1c,z1c;
      coord temp;
      int vert_num;
      int temp_vert;
      int counter;
    
      ifstream myfile ("cube.off");
      if (myfile.is_open())
      {
        myfile >> num_lines;
        //cout << "HERE: " << num_lines << endl;
        for(i=0;i<num_lines;i++)
        {
          getline (myfile,line);
          //cout << line << endl;
          myfile >> x1c;
          myfile >> y1c;
          myfile >> z1c;
          temp.x_c=x1c;
          temp.y_c=y1c;
          temp.z_c=z1c;
          cord.push_back(temp);
          //cout << "LINE IS: "<<x1c<<" "<<y1c<<" "<<z1c<<endl;
        }
    
        while(!myfile.eof())
        {
          myfile >> vert_num;
          for (i=0;i<vert_num;i++)
          {
            myfile >> temp_vert;
            temp_verts.push_back(temp_vert);
          }
          verts.push_back(temp_verts);
          temp_verts.clear();
        }
        //MUST DO BECAUSE OF EOF READ
        verts.pop_back();
        myfile.close();
      }
      else
      {
        cout << "Unable to open file";
      }
    }
    
    
    void mainMenu(int value)
    {
    
      switch(value)
      {
      case 0: exit(0);break;
      case 1: initMoves();break;
      }
    }
    
    void colorMenu(int value)
    {
      colorChoice = value;
      glutPostRedisplay();
    }
    
    void moveMenu(int value)
    {
      switch (value)
      {
      case 0: moveOrder = false; break;
      case 1: moveOrder = true; break;
      }
    }
    
    void keysMenu(int value)
    {
      switch (value)
      {
      case 0:key = false ; break;
      case 1:key = true ; break;
      }
    }
    
    
    void scaleMenu(int value)
    {
      switch (value)
      {
      case 0: scale_size += .1; break;
      case 1: scale_size -+ .1; break;
      case 2: scale_size = orig_scale_size; break;
      }
    }
    void displayMenu(int value)
    {
      switch (value)
      {
      case 0: wire_or_solid = true;break;
      case 1: wire_or_solid = false;break;
      }
    
    }
    void cullMenu(int value)
    {
      switch (value)
      {
      case 0: cull_or_not = true;break;
      case 1: cull_or_not = false;break;
    
      }
    
    }
    
    void makeMenus()
    {
    
      int topLevel, color, move, keys, scale,display_mode,cull;
      //#Increase the model scale by 10%.
      //# Decrease the model scale by 10%.
      //# Display the model in wireframe mode.
      //# Display the model in solid mode.
      //# Turn culling of backfaces on.
      //# Turn culling of backfaces off.
    
    
      scale = glutCreateMenu(scaleMenu);
      glutAddMenuEntry("+10%", 0);
      glutAddMenuEntry("-10%", 1);
      glutAddMenuEntry("Original", 2);
    
      display_mode = glutCreateMenu(displayMenu);
      glutAddMenuEntry("Wireframe", 0);
      glutAddMenuEntry("Solid", 1);
    
      cull = glutCreateMenu(cullMenu);
      glutAddMenuEntry("Culling ON", 0);
      glutAddMenuEntry("Culling OFF", 1);
    
      color = glutCreateMenu(colorMenu);
      glutAddMenuEntry("Red", 0);
      glutAddMenuEntry("Green", 1);
      glutAddMenuEntry("Blue", 2);
    
      move = glutCreateMenu(moveMenu);
      glutAddMenuEntry("Rotate Then Translate", 0);
      glutAddMenuEntry("Translate Then Rotate", 1);
    
      keys = glutCreateMenu(keysMenu);
      glutAddMenuEntry("Rotate", 0);
      glutAddMenuEntry("Translate", 1);
    
      topLevel=glutCreateMenu(mainMenu);
      glutAddSubMenu("Change Color", color);
      glutAddSubMenu("Change Movement", move);
      glutAddSubMenu("Change Keys",keys);
      glutAddSubMenu("Change Scale",scale);
      glutAddSubMenu("Change Display Mode",display_mode);
      glutAddSubMenu("Change Culling",cull);
      glutAddMenuEntry("Reset", 1);
      glutAddMenuEntry("Exit", 0);
    
      glutAttachMenu(GLUT_LEFT_BUTTON);
    
    }
    void keypress(unsigned char c, int x, int y)
    {
    
      if (!key)
      {
        switch (c)
        {
        case 'q': exit(0);
        case 'x': xrot += 5; break;
        case 'y': yrot += 5; break;
        case 'z': zrot += 5; break;
        case 'X': xrot -= 5; break;
        case 'Y': yrot -= 5; break;
        case 'Z': zrot -= 5; break;
        case 'r': initMoves(); break;
        }
      }
      else
      {
        switch (c)
        {
        case 'q': exit(0);
        case 'x': xtrans += .05; break;
        case 'y': ytrans += .05; break;
        case 'z': ztrans += .05; break;
        case 'X': xtrans -= .05; break;
        case 'Y': ytrans -= .05; break;
        case 'Z': ztrans -= .05; break;
        case 'r': initMoves(); break;
        }
      }
      glutPostRedisplay();
    }
    
    void cord_begin(int x, int y)
    {
      x_1 = x;
      y_1 = y;
      //cout << "ADDED: " << x << "  " << y << endl;
    
    }
    
    void spin(int x, int y)
    {
      float tempx, tempy;
    
      x_2 = x;
      y_2 = y;
    
    
      tempx = x_2 - x_1;
      tempx = tempx / 200;
      yspin = tempx;
    
      tempy = y_2 - y_1;
      tempy = tempy / 200;
      xspin = tempy;
    
      if(xrot > 90 && xrot < 270)
      {
        //cout << "IF 1" << endl;
        yspin = (-1) * tempx;
      }
      else if(xrot < -90 && xrot > -270)
      {
        //cout << "IF 2" << endl;
        yspin = (-1) * tempx;
      }
    
      if(yrot > 90 && yrot < 270)
      {
        //cout << "IF 3" << endl;
        xspin = (-1) * tempy;
      }
      else if(yrot < -90 && yrot > -270)
      {
        //cout << "IF 4" << endl;
        xspin = (-1) * tempy;
      }
    
      //cout << "SPIN: " << xspin << "  " << yspin << endl;
    
    
    }
    
    void move(int x, int y)
    {
      float mov_x, mov_y;
    
      oldMoveOrder = moveOrder;
      moveOrder = true;
    
      //cout << xrot << " " << yrot << " " << zrot << endl << endl;
    
      mov_x = x-250;
      mov_x = mov_x/125;
    
      mov_y = 250-y;
      mov_y = mov_y/125;
    
      ytrans = mov_y;
      xtrans = mov_x;
    
      if(xrot > 90 && xrot < 270)
      {
        ytrans = (-1) * mov_y;
      }
      else if(xrot < -90 && xrot > -270)
      {
        ytrans = (-1) * mov_y;
      }
    
      if(yrot > 90 && yrot < 270)
      {
        xtrans = (-1) * mov_x;
      }
      else if(yrot < -90 && yrot > -270)
      {
        xtrans = (-1) * mov_x;
      }
    
      //cout << xtrans << " " << ytrans << " " << ztrans << endl;
    
      glutPostRedisplay();
      moveOrder = oldMoveOrder;
    
    }
    
    void cord_end(int x, int y, int button)
    {
    
    
      switch (button)
      {
      case GLUT_MIDDLE_BUTTON:  spin(x,y);  break;
      }
    
    
    }
    
    void doMouse(int button, int state,int x, int y)
    {
      switch (button)
      {
      case GLUT_LEFT_BUTTON: button_down = button;  break;
      case GLUT_MIDDLE_BUTTON:button_down = button; glutSetCursor(GLUT_CURSOR_CYCLE); break;
      case GLUT_RIGHT_BUTTON:button_down = button;glutSetCursor(GLUT_CURSOR_CROSSHAIR);  break;
      }
    
      switch(state)
      {
      case GLUT_DOWN : cord_begin(x,y); break;
      case GLUT_UP :   cord_end(x,y,button); glutSetCursor(GLUT_CURSOR_LEFT_ARROW); break;
      }
      //cout << "GLOBALS ARE: " << x_1 << " " << y_1 << "    "<< x_2 << " " << y_2 << endl;
    
    
    }
    
    void mouseMotion(int x, int y)
    {
      if(button_down == GLUT_RIGHT_BUTTON)
      {
        move(x,y);
      }
    }
    
    void bound()
    {
      if(xrot >= 360 || xrot <= -360)
      {
        xrot = 0;
      }
      if(yrot >= 360 || yrot <= -360)
      {
        yrot = 0;
      }
    
    }
    
    void doIdle(void)
    {
      xrot += xspin;
      yrot += yspin;
      //cout << "ROT: " << xrot << "  " << yrot << endl;
      bound();
      glutPostRedisplay();
    
    }
    
    int main (int argc, char ** argv)
    {
    
      glutInit(&argc, argv);
      fileReady();
      show_keys();
      myinit();
      glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
      glutInitWindowSize(500,500);
      glutCreateWindow("Stan's Shape Program");
      glutDisplayFunc(display);
      glutIdleFunc(doIdle);
      glutKeyboardFunc(keypress);
      glutMouseFunc(doMouse);
      glutMotionFunc(mouseMotion);
      makeMenus();
      myinit();
      glutMainLoop();
    }

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