OpenGL鼠标拾取的实现：终于搞定（包括细节问题）

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游戏 J#

void OpenGL::pickRects(){
/*	GetCursorPos(&mouse);
	ScreenToClient(hWnd,&mouse);
	GLuint pickBuffer [32];
    GLint nPicks,vpArray[4];
	glRenderMode(GL_SELECT);
		glSelectBuffer(32,pickBuffer);
		glInitNames();
		//glPushName(-1);
		glMatrixMode(GL_PROJECTION);
		glPushMatrix();		   
			//glLoadIdentity();
			glGetIntegerv(GL_VIEWPORT,vpArray);
			gluPickMatrix(GLdouble(mouse.x),GLdouble(vpArray[3]-mouse.y),5.0,5.0,vpArray);
		//	glOrtho(0,1,0,1,0,1);
			//激活拾取区域。		  	
		//	gluOrtho2D(0,0,Width,Height);
		
		rects(GL_SELECT);
		glMatrixMode(GL_PROJECTION);
		int j;
		glGetIntegerv(GL_NAME_STACK_DEPTH,&j);
		cout<<j<<endl;
		glPopMatrix();
		glFlush();
	    nPicks=glRenderMode(GL_RENDER);
	    processPicks(nPicks,pickBuffer);
        //processPicks(nPicks,pickBuffer);
		*/
   GetCursorPos(&mouse);
   ScreenToClient(hWnd,&mouse);
   GLuint selectBuf[32];
   GLint hits;
   GLint viewport[4];
  
   glGetIntegerv(GL_VIEWPORT, viewport);

   glSelectBuffer(32, selectBuf);
   (void) glRenderMode(GL_SELECT);
   glInitNames();
   glPushName(0);
   glMatrixMode(GL_PROJECTION);

//下面这段代码可有可无，只是为了确保点击测试和实际绘图用的是同一个投影阵。

 glLoadIdentity();						// 重置当前指定的矩阵为单位矩阵
   gluPerspective							// 设置透视图
		( 53.0f,							// 透视角设置为 90 度
		  (GLfloat)Width/(GLfloat)Height,	// 窗口的宽与高比
		  0.1f,								// 视野透视深度:近点1.0f
		  3000.0f							// 视野透视深度:始点0.1f远点1000.0f
		);

   glPushMatrix();

下面的代码是最关键的地方，，注意：据测试：gluPickMatrix()意思并不是仅仅绘制一个拾取窗口。同时，

它也是一个投影矩阵变换！！～～～～如果使用第二个LoadIdentity()那么：前面的拾取矩阵就会失效！！

   glLoadIdentity();
/*  create 5x5 pixel picking region near cursor location */
   gluPickMatrix((GLdouble) mouse.x, (GLdouble) (viewport[3] - mouse.y),
                 5.0, 5.0, viewport);

//这个会促使上面那个PickMatrix失效！！切记～～～～
   //glLoadIdentity();						// 重置当前指定的矩阵为单位矩阵
   gluPerspective							// 设置透视图
		( 53.0f,							// 透视角设置为 90 度
		  (GLfloat)Width/(GLfloat)Height,	// 窗口的宽与高比
		  0.1f,								// 视野透视深度:近点1.0f
		  3000.0f							// 视野透视深度:始点0.1f远点1000.0f
		);
   rects(GL_SELECT);
   glPopMatrix();
   glFlush();
   hits = glRenderMode(GL_RENDER);
   processPicks(hits, selectBuf);
   int j;
   glGetIntegerv(GL_NAME_STACK_DEPTH,&j);
   int m;
}
void OpenGL::rects(GLenum mode)
{
if (mode == GL_SELECT)
    glLoadName(30);
    glPushMatrix();
	glTranslatef(-2,-1,-15);
	glColor3f(0.6f,0.2f,0.9f);
//	glRecti(0,0,100,100);
	Font->c3dtext("离开游戏",hFont,0.25f);
	glPopMatrix();
  /* glBegin(GL_QUADS);
   glColor3f(1.0, 1.0, 0.0);
   glVertex3i(2, 0, 0);
   glVertex3i(2, 6, 0);
   glVertex3i(6, 6, 0);
   glVertex3i(6, 0, 0);
   glEnd();
   */
   if (mode == GL_SELECT)
      glLoadName(20);
   glPushMatrix();
   	  glTranslatef(-2,1,-15);
	  glColor3f(0.6f,0.2f,0.9f);
	  Font->c3dtext("开始游戏",hFont,0.25f);
   glPopMatrix();
	  /*glBegin(GL_QUADS);
   glColor3f(0.0, 1.0, 1.0);
   glVertex3i(3, 2, -1);
   glVertex3i(3, 8, -1);
   glVertex3i(8, 8, -1);
   glVertex3i(8, 2, -1);
   glEnd();
   */
   /*
   if (mode == GL_SELECT)
      glLoadName(3);
   glBegin(GL_QUADS);
   glColor3f(1.0, 0.0, 1.0);
   glVertex3i(0, 2, -2);
   glVertex3i(0, 7, -2);
   glVertex3i(5, 7, -2);
   glVertex3i(5, 2, -2);
   glEnd();
	/*
   if(mode==GL_SELECT)
	glPushName(1);
  	glPushMatrix();
//	glTranslatef(0,0,-Height);
    glColor3f(0.0,1.0,0.0);
//	glPushName(20); 
	glTranslatef(-2,-1,-15);
//	glColor3f(0.6f,0.2f,0.9f);
//	glRecti(0,0,100,100);
	Font->c3dtext("离开游戏",hFont,0.25f);
	/*glBegin(GL_QUADS);
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-Width/2, -Height/2,  -0.0f);// 前
		glTexCoord2f(1.0f, 0.0f); glVertex3f( Width/2,-Height/2,  -0.0f);
		glTexCoord2f(1.0f, 1.0f); glVertex3f( Width/2,  Height/2,  -0.0f);
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-Width/2,  Height/2,  -0.0f);
    glEnd();

 //   glColor3f(1.0,0.0,0.0);
//	glTranslatef(-2,1,-15);
	glColor3f(0.6f,0.2f,0.9f);
//	Font->c3dtext("开始游戏",hFont,0.25f);
	glPopMatrix();		
   if(mode==GL_SELECT)
	glPushName(2);
   	glPushMatrix();
   // glTranslatef(0,0,-Height);
//	glColor3f(0.0,1.0,0.0);
//	glPushName(20); 
	glTranslatef(-2,-1,-15);
	glColor3f(0.6f,0.2f,0.9f);
//	glRecti(0,0,100,100);
	Font->c3dtext("离开游戏",hFont,0.25f);

	glBegin(GL_QUADS);
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-Width/2, -Height/2,  -0.0f);// 前
		glTexCoord2f(1.0f, 0.0f); glVertex3f( Width/2,-Height/2,  -0.0f);
		glTexCoord2f(1.0f, 1.0f); glVertex3f( Width/2,  Height/2,  -0.0f);
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-Width/2,  Height/2,  -0.0f);
    glEnd();

	glPopMatrix();
	*/
}
void OpenGL::processPicks(GLint hits,GLuint buffer[]){
	rects(GL_RENDER);
	cout<<hits<<endl;
 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");
   }
}

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