Opengl 鼠标点击矩形

Question

伙计们，我在使用 glut 鼠标功能时遇到了这个程序的问题。我在做什么 在屏幕上绘制一个矩形，在鼠标功能中，我将像素坐标转换为宽度为 600 和高度为 500 的世界坐标如何确定鼠标点击这些矩形。
代码：

#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

我想你可以通过这个来使用 GLUT_STENCIL 你可以通过索引来指示你场景中的所有对象

 #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;
    }

它适用于我在 Mac 上，但我认为也应该适用于 freeglut