Opengl鼠標點擊矩形

Question

夥計們，我在使用過量鼠標功能的程序中遇到了一個問題。我正在做一個矩形繪製在屏幕上，並在鼠標功能我將像素座標轉換爲世界座標與寬度600和高度500我想要什麼時用戶點擊給定的矩形顏色將是紅色的，但我如何執行此任務如何確定鼠標點擊這些矩形。
代碼：

#include <cstdlib> 
#include<GL\freeglut.h> 
#include <iostream> 
using namespace std; 

    float xWorldCoordinate = 0.0f; 
    float yWorldCoordinate = 0.0f; 
    float r = 0.0f; 
    float g = 0.0f; 
    float b = 0.0f; 
    float r1 = 0.0f; 
    float g1 = 0.0f; 
    float b1 = 0.0f; 
    bool isRed = false; 

    void init(void) { 

     glClearColor(31.0f/255, 28.0f/255, 44.0f/255, 0.0f); 
     glMatrixMode(GL_PROJECTION); 
     glLoadIdentity(); 
     glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0); 
    } 

    void MouseButton(int button, int action, int xPixel, int yPixel) { 

     if (button == GLUT_LEFT_BUTTON && action == GLUT_DOWN) { 
      yPixel = 500 - yPixel; 
      xWorldCoordinate = (xPixel/600.0f) * 2; 
      yWorldCoordinate = (yPixel/400.0f) * 2; 
      xWorldCoordinate = -1 + xWorldCoordinate; 
      yWorldCoordinate = -1 + yWorldCoordinate; 

      int index1 = 0; 
      int index2 = 0; 
      //Index1 
      glReadPixels(xPixel, yPixel, 1, 1, GL_STENCIL_INDEX, GL_UNSIGNED_INT, &index1);// Read pixel under mouse's cursor and read information from stencil buffer to index when it rectangle index should be equal to 1 


      if (index1 == 1) { 
       isRed = !isRed; 
       if (isRed) { 
        r = 0.0f; 

       } 
       else { 
        r = 1.0f; 
       } 


       //Index 2 
      // glReadPixels(xPixel, yPixel, 1, 1, GL_STENCIL_INDEX, GL_UNSIGNED_INT, &index2); 
      } 
     } 

     glutPostRedisplay(); 
    } 

    void Rectangles(void) { 

     glStencilFunc(GL_ALWAYS, 1, -1); //set front and back function and reference value for stencil testing 
     glBegin(GL_POLYGON); 

     glColor3f(r, g, b); 
     glVertex2f(-0.1f, 0.1f); 
     glVertex2f(-0.1f, -0.1f); 
     glVertex2f(0.1f, -0.1f); 
     glVertex2f(0.1f, 0.1f); 
     glEnd(); 

     //2nd Rectangle 
     glStencilFunc(GL_ALWAYS, 2, -1); 
     glBegin(GL_POLYGON); 
     glColor3f(r1, g1, b1); 
     glVertex2f(0.66f, 0.84f); 
     glVertex2f(0.87f, 0.84f); 
     glVertex2f(0.87f, 0.66f); 
     glVertex2f(0.66f, 0.66f); 
     glEnd(); 
    } 
    void Display(void) { 
     glClearStencil(0); // specifies the index used by glClear to clear the stencil buffer 
     glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT); 
     glEnable(GL_STENCIL_TEST); 
     glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE); 
     glMatrixMode(GL_MODELVIEW); 
     glLoadIdentity(); 
     Rectangles(); 
     glFlush(); 
    } 

    int main(int argc, char **argv) { 

     glutInit(&argc, argv); 
     glutInitDisplayMode(GLUT_STENCIL); //Bit mask to select a window with a stencil buffer. 
     glutInitWindowSize(600, 500); 
     glutInitWindowPosition(100, 100); 
     glutCreateWindow("Mouse"); 
     init(); 
     glutDisplayFunc(&Display); 
     glutMouseFunc(&MouseButton); 
     glutMainLoop(); 

     return EXIT_SUCCESS; 
    } 

Answer 1

我想你可以通過這個使用GLUT_STENCIL您可以通過索引上註明你是場景中所有對象

#if defined(__APPLE__) || defined(MACOSX) 
    #include <GLUT/glut.h> 
#else 
    #include <GL\freeglut.h> 
#endif 
#include <cstdlib> 
#include <iostream> 
using namespace std; 

using namespace std; 

    float xWorldCoordinate = 0.0f; 
    float yWorldCoordinate = 0.0f; 
    float r = 0.0f; 
    float g = 0.0f; 
    float b = 0.0f; 
    float r1 = 0.0f; 
    float g1 = 0.0f; 
    float b1 = 0.0f; 
    bool isRed = false; 
    bool isBlue = false; 
    void init(void) { 

     glClearColor(31.0f/255, 28.0f/255, 44.0f/255, 0.0f); 
     glMatrixMode(GL_PROJECTION); 
     glLoadIdentity(); 
     glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0); 
    } 

    void MouseButton(int button, int action, int xPixel, int yPixel) { 

     if (button == GLUT_LEFT_BUTTON && action == GLUT_DOWN) { 
      yPixel = glutGet(GLUT_WINDOW_HEIGHT) - yPixel; 

      int * index = new int[1]; 
      //Index1 
      glReadPixels(xPixel, yPixel, 1, 1, GL_STENCIL_INDEX, GL_UNSIGNED_INT, index);// Read pixel under mouse's cursor and read information from stencil buffer to index when it rectangle index should be equal to 1 


      if (index[0] == 1) { 
       isRed = !isRed; 
       if (isRed) { 
        r = 1.0f; 

       } 
       else { 
        r = 0.0f; 
       } 
       //Index 2 
      // glReadPixels(xPixel, yPixel, 1, 1, GL_STENCIL_INDEX, GL_UNSIGNED_INT, &index2); 
      }else if(index[0] == 2){ 
      isBlue = !isBlue; 
      if (isBlue) { 
       b1 = 1.0f; 

      } 
      else { 
       b1 = 0.0f; 
      } 
      } 
      delete index; 
     } 

     glutPostRedisplay(); 
    } 

    void Rectangles(void) { 

     glStencilFunc(GL_ALWAYS, 1, -1); //set front and back function and reference value for stencil testing 
     glBegin(GL_POLYGON); 

     glColor3f(r, g, b); 
     glVertex2f(-0.1f, 0.1f); 
     glVertex2f(-0.1f, -0.1f); 
     glVertex2f(0.1f, -0.1f); 
     glVertex2f(0.1f, 0.1f); 
     glEnd(); 

     //2nd Rectangle 
     glStencilFunc(GL_ALWAYS, 2, -1); 
     glBegin(GL_POLYGON); 
     glColor3f(r1, g1, b1); 
     glVertex2f(0.66f, 0.84f); 
     glVertex2f(0.87f, 0.84f); 
     glVertex2f(0.87f, 0.66f); 
     glVertex2f(0.66f, 0.66f); 
     glEnd(); 
    } 
    void Display(void) { 
     glClearStencil(0); // specifies the index used by glClear to clear the stencil buffer 
     glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT); 
     glEnable(GL_STENCIL_TEST); 
     glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE); 
     glMatrixMode(GL_MODELVIEW); 
     glLoadIdentity(); 
     Rectangles(); 
     glFlush(); 
    } 

    int main(int argc, char **argv) { 

     glutInit(&argc, argv); 
     glutInitDisplayMode(GLUT_STENCIL); //Bit mask to select a window with a stencil buffer. 
     glutInitWindowSize(600, 500); 
     glutInitWindowPosition(100, 100); 
     glutCreateWindow("Mouse"); 
     init(); 
     glutDisplayFunc(&Display); 
     glutMouseFunc(&MouseButton); 
     glutMainLoop(); 

     return EXIT_SUCCESS; 
    } 

它爲我在Mac上，但我覺得應該一起工作freeglut too