Problem occuring with C++ (OpenGL)

This is a discussion on Problem occuring with C++ (OpenGL) within the C++ Programming forums, part of the General Programming Boards category; Hi, there. I'm having some troubles with my C++ code and I really don't know where it went wrong. Can ...

  1. #1
    Registered User
    Join Date
    Apr 2013
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    1

    Problem occuring with C++ (OpenGL)

    Hi, there.

    I'm having some troubles with my C++ code and I really don't know where it went wrong. Can somebody help me, please?

    It was expected to draw a square and change the color when the user press some keys. The window's background should be white and as the user press the keys the color of the square should change from red to blue and when the user press the key again the color should go back to red as you can see it with the code bellow.
    Can somebody can help me with that?

    Code:
    #include <windows.h>                                                           
    #include <gl/glut.h>                                                           
                                                                                   
    // Função callback chamada para fazer o desenho                                
    void Desenha(void)                                                             
    {                                                                              
         glMatrixMode(GL_MODELVIEW);                                               
         glLoadIdentity();                                                         
                                                                                   
         // Limpa a janela de visualização com a cor de fundo especificada         
         glClear(GL_COLOR_BUFFER_BIT);                                             
                                                                                   
         // Especifica que a cor corrente é vermelha                               
         //         R     G     B                                                  
         glColor3f(1.0f, 0.0f, 0.0f);                                              
                                                                                   
         // Desenha um quadrado preenchido com a cor corrente                      
         glBegin(GL_QUADS);                                                        
                   glVertex2i(30,226);                                             
                   glVertex2i(226,30);                                             
                   // Especifica que a cor corrente é azul                         
                   glColor3f(0.0f, 0.0f, 1.0f);                                    
                   glVertex2i(30,226);                                             
                   glVertex2i(226,30);                                             
         glEnd();                                                                  
                                                                                   
         // Executa os comandos OpenGL                                             
         glFlush();                                                                
    }                                                                              
                                                                                   
    // Inicializa parâmetros de rendering                                          
    void Inicializa (void)                                                         
    {                                                                              
        // Define a cor de fundo da janela de visualização como branca             
          glClearColor(1.0f,1.0f,1.0f,0.5f);                                    
    }                                                                              
                                                                                   
    // Função callback chamada quando o tamanho da janela é alterado               
    void AlteraTamanhoJanela(GLsizei w, GLsizei h)                                 
    {                                                                              
                       // Evita a divisao por zero                                 
                       if(h == 0) h = 1;                                           
                                                                                   
                       // Especifica as dimensões da Viewport                      
                       glViewport(0, 0, w, h);                                     
                                                                                   
                       // Inicializa o sistema de coordenadas                      
                       glMatrixMode(GL_PROJECTION);                                
                       glLoadIdentity();                                           
                                                                                   
                       // Estabelece a janela de seleção (left, right, bottom, top)
                       if (w <= h)                                                 
                               gluOrtho2D (0.0f, 250.0f, 0.0f, 250.0f*h/w);        
                       else                                                        
                               gluOrtho2D (0.0f, 250.0f*w/h, 0.0f, 250.0f);        
    }                                                                              
                                                                                   
                                                                                   
                                                                                   
                                                                                   
    // Função callback chamada para gerenciar eventos de teclado                   
    void GerenciaTeclado(unsigned char key, int x, int y)                          
    {                                                                           
        switch (key) {                                                             
                case 97:                                                           
                case 'a':// muda a cor corrente para vermelho                      
                         glColor3f(1.0f, 0.0f, 0.0f);                              
                         break;                                                    
                case 118:                                                          
                case 'v':// muda a cor corrente para verde                         
                         glColor3f(0.0f, 0.0f, 1.0f);                              
                         break;                                                    
                case 27:                                                           
                case 'esc':// fecha a tela                                         
                       exit(0);                                                    
                         break;                                                    
        }                                                                          
        glutPostRedisplay();                                                       
       }        
                                                                       
    // Programa Principal                                                          
    int main(void)                                                                 
    {                                                                              
         glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);                              
         glutInitWindowSize(256,256);                                              
         glutInitWindowPosition(10,10);                                            
         glutCreateWindow("Quadrado");                                             
         glutDisplayFunc(Desenha);                                                 
         glutReshapeFunc(AlteraTamanhoJanela);                                     
         Inicializa();                                                             
         glutMainLoop();                                                           
    }

  2. #2
    Registered User
    Join Date
    Dec 2006
    Location
    Canada
    Posts
    3,183
    What is it doing?

    And why glColor3f() between glBegin(GL_QUADS) and glEnd()?

    Code:
    case 'esc':
    'esc' is not one character.

  3. #3
    Registered User
    Join Date
    Jan 2011
    Location
    Slovakia
    Posts
    21
    Hi,

    Firstly you are using GLUT.

    Secondly you are calling the key hit routine at all in your main loop.

    Have a look at the Lighthouse tutorials for keyboard movement.

    Keyboard » Lighthouse3d.com

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