OpenGL: 创建名字栈

      创建名字栈有4个函数组成，glInitNames, glPushName, glPopName, glLoadName. 以下是一个例子。

#include <stdio.h>#include <math.h>#include <Windows.h>#include <gl/GL.h>#include <gl/GLU.h>#include <gl/glut.h>#include <gl/GLAux.h>#pragma comment(lib, "OpenGL32.lib")#pragma comment(lib, "GLU32.lib")#pragma comment(lib, "Glut32.lib")void drawTriangle(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2, GLfloat x3, GLfloat y3, GLfloat z){glBegin(GL_TRIANGLES);glVertex3f(x1, y1, z);glVertex3f(x2, y2, z);glVertex3f(x3, y3, z);glEnd();}void drawViewVolume(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2, GLfloat z1, GLfloat z2){glColor3f(1.0, 1.0, 1.0);glBegin(GL_LINE_LOOP);glVertex3f(x1, y1, -z1);glVertex3f(x2, y1, -z1);glVertex3f(x2, y2, -z1);glVertex3f(x1, y2, -z1);glEnd();glBegin(GL_LINE_LOOP);glVertex3f(x1, y1, -z2);glVertex3f(x2, y1, -z2);glVertex3f(x2, y2, -z2);glVertex3f(x1, y2, -z2);glEnd();glBegin(GL_LINES);glVertex3f(x1, y1, -z1);glVertex3f(x1, y1, -z2);glVertex3f(x1, y2, -z1);glVertex3f(x1, y2, -z2);glVertex3f(x2, y1, -z1);glVertex3f(x2, y1, -z2);glVertex3f(x2, y2, -z1);glVertex3f(x2, y2, -z2);glEnd();}void drawScene(){glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(40.0, 4.0 / 3.0, 1.0, 100.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt(7.5, 7.5, 12.5, 2.5, 2.5, -5.0, 0.0, 1.0, 0.0);glColor3f(0.0, 1.0, 0.0);drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -5.0);glColor3f(1.0, 0.0, 0.0);drawTriangle(2.0, 7.0, 3.0, 7.0, 2.5, 8.0, -5.0);glColor3f(1.0, 1.0, 0.0);drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, 0.0);drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -10.0);drawViewVolume(0.0, 5.0, 0.0, 5.0, 0.0, 10.0);}void processHits(GLint hits, GLuint buffer[]){unsigned int i, j;GLuint names, *ptr;printf("hits = %d \n", hits);ptr = (GLuint*)buffer;for (i = 0; i < hits; i++){names = *ptr;printf(" number of names for hit = %d \n ", names);ptr++;printf(" z1 is %g;", (float)*ptr / 0x7fffffff);ptr++;printf(" z2 is %g \n", (float)*ptr / 0x7fffffff);ptr++;printf(" the name is ");for (j = 0; j < names; j++){printf("%d ", *ptr);ptr++;}printf("\n ");}}#define BUFSIZE 512void selectObjects(){GLuint selectBuf[BUFSIZE];GLint hits;glSelectBuffer(BUFSIZE, selectBuf);(void)glRenderMode(GL_SELECT);glInitNames();glPushName(0);glPushMatrix();glMatrixMode(GL_PROJECTION);glLoadIdentity();glOrtho(0.0, 5.0, 0.0, 5.0, 0.0, 10.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();glLoadName(1);drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -5.0);glLoadName(2);drawTriangle(2.0, 7.0, 3.0, 7.0, 2.5, 8.0, -5.0);glLoadName(3);drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, 0.0);drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -10.0);glPopMatrix();glFlush();hits = glRenderMode(GL_RENDER);processHits(hits, selectBuf);}void init(){glEnable(GL_DEPTH_TEST);glShadeModel(GL_FLAT);}void display(){glClearColor(0.0, 0.0, 0.0, 0.0);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);drawScene();selectObjects();glFlush();}void reshape(int w, int h){glViewport(0, 0, w, h);glMatrixMode(GL_PROJECTION);glLoadIdentity();glOrtho(0.0, 5.0, 0.0, 5.0, 0.0, 10.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();}void keyboard(unsigned char key, int x, int y){switch(key){case 'c':case 'C':glutPostRedisplay();break;case 27:exit(0);break;default:break;}}int main(int argc, char **argv){glutInit(&argc, argv);glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE | GLUT_DEPTH);glutInitWindowPosition(100, 100);glutInitWindowSize(200, 200);glutCreateWindow(argv[0]);init();glutReshapeFunc(reshape);glutKeyboardFunc(keyboard);glutDisplayFunc(display);glutMainLoop();return 0;}

运行结果如下：