藍(lán)寶書 第三章

單緩沖與雙緩沖

glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);單緩沖 相關(guān)代碼見例3.12

直接將圖像改變顯示在畫布上，使用glFlush()提交緩沖

glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);雙緩沖

一般圖像改變在后臺緩沖區(qū)，使用glutSwapBuffers()將后臺緩沖提交至前臺緩沖區(qū)

void glDrawBuffer(Glenummode) 該函數(shù)可設(shè)置當(dāng)前改變前臺緩沖區(qū)還是后臺緩沖區(qū)

glDrawBuffer(GL_FRONT)  前臺

glDrawBuffer(GL_BACK)  后臺

顏色緩沖區(qū)與深度緩沖區(qū)

glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH)

上述語句初始化了顏色緩沖區(qū)、雙緩沖區(qū)以及深度緩沖區(qū)

若未啟用深度緩沖區(qū)（glDisable(GL_DEPTH_TEST)），則深度數(shù)據(jù)也會寫入顏色緩沖區(qū)，使用glDepthMask(GL_FALSE)禁止寫入，第六章詳細(xì)講解

剪刀盒（類似于opencv的感興趣區(qū)域）

只對剪刀盒范圍內(nèi)進(jìn)行處理

glEnable(GL_SCISSOR_TEST);啟用剪刀盒

void glScissor(GLintx, GLint y, GLsizeiwidth, GLsizei height); 設(shè)置剪刀盒范圍

相關(guān)代碼見例3.13

模板緩沖區(qū)

類似于噴油漆，在紙上鏤空一個(gè)模板，再噴上油漆，下面的紙上只有鏤空部分才有顏色。

glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_STENCIL);初始化模板緩沖區(qū)glEnable(GL_STENCIL_TEST);啟用模板緩沖區(qū)

void glStencilFunc(GLenumfunc, GLint ref, GLuint mask);設(shè)置模板參考：

點(diǎn)擊打開鏈接

點(diǎn)擊打開鏈接

相關(guān)代碼見例3.14

例3.12 單緩沖區(qū)示例（單擊窗口進(jìn)行新的緩沖，增大了圖形半徑）

#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);//顯示回調(diào)函數(shù)  	glutReshapeFunc(ChangeSize);//窗口大小變形回調(diào)函數(shù)  	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);//顯示回調(diào)函數(shù)  	glutReshapeFunc(ChangeSize);//窗口大小變形回調(diào)函數(shù)  	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);//顯示回調(diào)函數(shù)  	glutReshapeFunc(ChangeSize);//窗口大小變形回調(diào)函數(shù)  	SetupRC();	glutMainLoop();	return 0;}