OpenGL 学习笔记3_5(缓冲区相关) 模板缓冲区待详细分析

蓝宝书 第三章

单缓冲与双缓冲

glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);单缓冲 相关代码见例3.12

直接将图像改变显示在画布上，使用glFlush()提交缓冲

glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);双缓冲

一般图像改变在后台缓冲区，使用glutSwapBuffers()将后台缓冲提交至前台缓冲区

void glDrawBuffer(Glenummode) 该函数可设置当前改变前台缓冲区还是后台缓冲区

glDrawBuffer(GL_FRONT)  前台

glDrawBuffer(GL_BACK)  后台

颜色缓冲区与深度缓冲区

glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH)

上述语句初始化了颜色缓冲区、双缓冲区以及深度缓冲区

若未启用深度缓冲区（glDisable(GL_DEPTH_TEST)），则深度数据也会写入颜色缓冲区，使用glDepthMask(GL_FALSE)禁止写入，第六章详细讲解

剪刀盒（类似于opencv的感兴趣区域）

只对剪刀盒范围内进行处理

glEnable(GL_SCISSOR_TEST);启用剪刀盒

void glScissor(GLintx, GLint y, GLsizeiwidth, GLsizei height); 设置剪刀盒范围

相关代码见例3.13

模板缓冲区

类似于喷油漆，在纸上镂空一个模板，再喷上油漆，下面的纸上只有镂空部分才有颜色。

glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_STENCIL);初始化模板缓冲区glEnable(GL_STENCIL_TEST);启用模板缓冲区

void glStencilFunc(GLenumfunc, GLint ref, GLuint mask);设置模板参考：

点击打开链接

点击打开链接

相关代码见例3.14

例3.12 单缓冲区示例（单击窗口进行新的缓冲，增大了图形半径）

#include <windows.h>  #include <math.h>  #include <GL/GL.h>  #include <GL/GLU.h>  #include <GL/glut.h>  #define GL_PI 3.1415f  // This function does any needed initialization on the rendering  void RenderScene(void){	static GLdouble dRadius = 15;	static GLdouble dAngle = 0.0;	// Clear blue window	glClearColor(0.0f, 0.0f, 1.0f, 0.0f);	if (dAngle == 0.0)		glClear(GL_COLOR_BUFFER_BIT);	glBegin(GL_POINTS);	glVertex2d(dRadius * cos(dAngle), dRadius * sin(dAngle));	glEnd();	dRadius *= 1.01;	dAngle += 0.2;	if (dAngle > 30.0)	{		dRadius = 15;		dAngle = 0.0;	}	glFlush();}void SetuPRC(){	// Black background	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);	// Set drawing color to red	glColor3f(1.0f, 0.0f, 0.0f);	//glPolygonMode(GL_BACK, GL_LINE);	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); 	// Enable polygon stippling	//glEnable(GL_POLYGON_STIPPLE);	// Specify a specific stipple pattern	//glPolygonStipple(fire);}void ChangeSize(GLsizei w, GLsizei h){	GLfloat nRange = 100.0f;	// Prevent a divide by zero  	if (h == 0)		h = 1;	// Set Viewport to window dimensions  	glViewport(0, 0, w, h);	// Reset projection matrix stack  	glMatrixMode(GL_PROJECTION);	glLoadIdentity();	// Establish clipping volume (left, right, bottom, top, near, far)  	if (w <= h)		glOrtho(-nRange, nRange, -nRange*h / w, nRange*h / w, -nRange, nRange);	else		glOrtho(-nRange*w / h, nRange*w / h, -nRange, nRange, -nRange, nRange);	// Reset Model view matrix stack  	glMatrixMode(GL_MODELVIEW);	glLoadIdentity();}int main(int argc, char* argv[]){	glutInit(&argc, argv);	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA);	glutInitWindowSize(800, 600);	glutCreateWindow("Bounce");	glutDisplayFunc(RenderScene);//显示回调函数  	glutReshapeFunc(ChangeSize);//窗口大小变形回调函数  	SetupRC();	glutMainLoop();	return 0;}例3.13 剪刀盒示例
#include <windows.h>  #include <math.h>  #include <GL/GL.h>  #include <GL/GLU.h>  #include <GL/glut.h>  #define GL_PI 3.1415f  // This function does any needed initialization on the rendering  void RenderScene(void){	glClearColor(0.0f, 0.0f, 1.0f, 0.0f);	glClear(GL_COLOR_BUFFER_BIT);	// Now set scissor to smaller red sub region	glClearColor(1.0f, 0.0f, 0.0f, 0.0f);	glScissor(100, 100, 600, 400);	glEnable(GL_SCISSOR_TEST);	glClear(GL_COLOR_BUFFER_BIT);	// Finally, an even smaller green rectangle	glClearColor(0.0f, 1.0f, 0.0f, 0.0f);	glScissor(200, 200, 400, 200);	glClear(GL_COLOR_BUFFER_BIT);	// Turn scissor back off for next render	glDisable(GL_SCISSOR_TEST);	glutSwapBuffers();}void SetupRC(){	// Black background	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);	// Set drawing color to red	glColor3f(1.0f, 0.0f, 0.0f);	//glPolygonMode(GL_BACK, GL_LINE);	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); 	// Enable polygon stippling	//glEnable(GL_POLYGON_STIPPLE);	// Specify a specific stipple pattern	//glPolygonStipple(fire);}void ChangeSize(GLsizei w, GLsizei h){	GLfloat nRange = 100.0f;	// Prevent a divide by zero  	if (h == 0)		h = 1;	// Set Viewport to window dimensions  	glViewport(0, 0, w, h);	// Reset projection matrix stack  	glMatrixMode(GL_PROJECTION);	glLoadIdentity();	// Establish clipping volume (left, right, bottom, top, near, far)  	if (w <= h)		glOrtho(-nRange, nRange, -nRange*h / w, nRange*h / w, -nRange, nRange);	else		glOrtho(-nRange*w / h, nRange*w / h, -nRange, nRange, -nRange, nRange);	// Reset Model view matrix stack  	glMatrixMode(GL_MODELVIEW);	glLoadIdentity();}int main(int argc, char* argv[]){	glutInit(&argc, argv);	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);	glutInitWindowSize(800, 600);	glutCreateWindow("Bounce");	glutDisplayFunc(RenderScene);//显示回调函数  	glutReshapeFunc(ChangeSize);//窗口大小变形回调函数  	SetupRC();	glutMainLoop();	return 0;}例3.14 模板示例
#include <windows.h>  #include <math.h>  #include <GL/GL.h>  #include <GL/GLU.h>  #include <GL/glut.h>  #define GL_PI 3.1415f  // This function does any needed initialization on the rendering  void RenderScene(void){	GLdouble dRadius = 0.1; // Initial radius of spiral	GLdouble dAngle; // Looping variable	// Clear blue window	glClearColor(0.0f, 0.0f, 1.0f, 0.0f);	// Use 0 for clear stencil, enable stencil test	glClearStencil(0.0f);	glEnable(GL_STENCIL_TEST);	// Clear color and stencil buffer	glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);	// All drawing commands fail the stencil test, and are not	// drawn, but increment the value in the stencil buffer.	glStencilFunc(GL_NEVER, 0x0, 0x0);	glStencilOp(GL_INCR, GL_INCR, GL_INCR);	// Spiral pattern will create stencil pattern	// Draw the spiral pattern with white lines. We	// make the lines white to demonstrate that the	// stencil function prevents them from being drawn	glColor3f(1.0f, 1.0f, 1.0f);	glBegin(GL_LINE_STRIP);	for (dAngle = 0; dAngle < 400.0; dAngle += 0.1)	{		glVertex2d(dRadius * cos(dAngle), dRadius * sin(dAngle));		dRadius *= 1.002;	}	glEnd();	// Now, allow drawing, except where the stencil pattern is 0x1	// and do not make any further changes to the stencil buffer	glStencilFunc(GL_NOTEQUAL, 0x1, 0x1);	glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);	// Now draw red bouncing square	// (x and y) are modified by a timer function	glColor3f(1.0f, 0.0f, 0.0f);	glRectf(0, 0, 100, 100);	// All done, do the buffer swap	glutSwapBuffers();}void SetupRC(){	// Black background	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);	// Set drawing color to red	glColor3f(1.0f, 0.0f, 0.0f);	//glPolygonMode(GL_BACK, GL_LINE);	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); 	// Enable polygon stippling	//glEnable(GL_POLYGON_STIPPLE);	// Specify a specific stipple pattern	//glPolygonStipple(fire);}void ChangeSize(GLsizei w, GLsizei h){	GLfloat nRange = 100.0f;	// Prevent a divide by zero  	if (h == 0)		h = 1;	// Set Viewport to window dimensions  	glViewport(0, 0, w, h);	// Reset projection matrix stack  	glMatrixMode(GL_PROJECTION);	glLoadIdentity();	// Establish clipping volume (left, right, bottom, top, near, far)  	if (w <= h)		glOrtho(-nRange, nRange, -nRange*h / w, nRange*h / w, -nRange, nRange);	else		glOrtho(-nRange*w / h, nRange*w / h, -nRange, nRange, -nRange, nRange);	// Reset Model view matrix stack  	glMatrixMode(GL_MODELVIEW);	glLoadIdentity();}int main(int argc, char* argv[]){	glutInit(&argc, argv);	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);	glutInitWindowSize(800, 600);	glutCreateWindow("Bounce");	glutDisplayFunc(RenderScene);//显示回调函数  	glutReshapeFunc(ChangeSize);//窗口大小变形回调函数  	SetupRC();	glutMainLoop();	return 0;}