openGL的程序
帮我把这个程序的每一句做个注释吧
/*
* Copyright (c) 1993-1999, Silicon Graphics, Inc.
* ALL RIGHTS RESERVED
* Permission to use, copy, modify, and distribute this software for
* any purpose and without fee is hereby granted, provided that the above
* copyright notice appear in all copies and that both the copyright notice
* and this permission notice appear in supporting documentation, and that
* the name of Silicon Graphics, Inc. not be used in advertising
* or publicity pertaining to distribution of the software without specific,
* written prior permission.
*
* THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
* AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
* FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SILICON
* GRAPHICS, INC. BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
* SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
* KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
* LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
* THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC. HAS BEEN
* ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
* POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
*
* US Government Users Restricted Rights
* Use, duplication, or disclosure by the Government is subject to
* restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
* (c)(1)(ii) of the Rights in Technical Data and Computer Software
* clause at DFARS 252.227-7013 and/or in similar or successor
* clauses in the FAR or the DOD or NASA FAR Supplement.
* Unpublished-- rights reserved under the copyright laws of the
* United States. Contractor/manufacturer is Silicon Graphics,
* Inc., 2011 N. Shoreline Blvd., Mountain View, CA 94039-7311.
*
* OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
*/
/* accpersp.c
* Use the accumulation buffer to do full-scene antialiasing
* on a scene with perspective projection, using the special
* routines accFrustum() and accPerspective().
*/
#include <GL/glut.h> //使用GLUT来管理窗口
#include <stdlib.h> //标准C语言库系统调用
#include <math.h> //声明该主程序调用数学函数库
#include "jitter.h"
#define PI_ 3.14159265358979323846
/* accFrustum()
* The first 6 arguments are identical to the glFrustum() call.
*
* pixdx and pixdy are anti-alias jitter in pixels.
* Set both equal to 0.0 for no anti-alias jitter.
* eyedx and eyedy are depth-of field jitter in pixels.
* Set both equal to 0.0 for no depth of field effects.
*
* focus is distance from eye to plane in focus.
* focus must be greater than, but not equal to 0.0.
*
* Note that accFrustum() calls glTranslatef(). You will
* probably want to insure that your ModelView matrix has been
* initialized to identity before calling accFrustum().
*/
void accFrustum(GLdouble left, GLdouble right, GLdouble bottom,
GLdouble top, GLdouble zNear, GLdouble zFar, GLdouble pixdx,
GLdouble pixdy, GLdouble eyedx, GLdouble eyedy, GLdouble focus)
{
GLdouble xwsize, ywsize;
GLdouble dx, dy;
GLint viewport[4];
glGetIntegerv (GL_VIEWPORT, viewport);
xwsize = right - left;
ywsize = top - bottom;
dx = -(pixdx*xwsize/(GLdouble) viewport[2] + eyedx*zNear/focus);
dy = -(pixdy*ywsize/(GLdouble) viewport[3] + eyedy*zNear/focus);
glMatrixMode(GL_PROJECTION); //指明当前矩阵为GL_PROJECTION
glLoadIdentity(); //将当前矩阵置换为单位阵
glFrustum (left + dx, right + dx, bottom + dy, top + dy, zNear, zFar); //设置其投影变换
glMatrixMode(GL_MODELVIEW); //开始模型视图变换
glLoadIdentity();
glTranslatef (-eyedx, -eyedy, 0.0); //绘图位置
}
/* accPerspective()
*
* The first 4 arguments are identical to the gluPerspective() call.
* pixdx and pixdy are anti-alias jitter in pixels.
* Set both equal to 0.0 for no anti-alias jitter.
* eyedx and eyedy are depth-of field jitter in pixels.
* Set both equal to 0.0 for no depth of field effects.
*
* focus is distance from eye to plane in focus.
* focus must be greater than, but not equal to 0.0.
*
* Note that accPerspective() calls accFrustum().
*/
void accPerspective(GLdouble fovy, GLdouble aspect,
GLdouble zNear, GLdouble zFar, GLdouble pixdx, GLdouble pixdy,
GLdouble eyedx, GLdouble eyedy, GLdouble focus)
{
GLdouble fov2,left,right,bottom,top;
fov2 = ((fovy*PI_) / 180.0) / 2.0;
top = zNear / (cos(fov2) / sin(fov2));
bottom = -top;
right = top * aspect;
left = -right;
accFrustum (left, right, bottom, top, zNear, zFar,
pixdx, pixdy, eyedx, eyedy, focus);
}
/* Initialize lighting and other values.
*/
void init(void)
{
GLfloat mat_ambient[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat light_position[] = { 0.0, 0.0, 10.0, 1.0 };
GLfloat lm_ambient[] = { 0.2, 0.2, 0.2, 1.0 };
glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient); //定义材质的环境反射光
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
glMaterialf(GL_FRONT, GL_SHININESS, 50.0); //设置光亮度
glLightfv(GL_LIGHT0, GL_POSITION, light_position); //定义光源位置坐标
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, lm_ambient); ////全局环境光
glEnable(GL_LIGHTING); //启动光照
glEnable(GL_LIGHT0); //使光源GL_LIGHT0有效;
glEnable(GL_DEPTH_TEST); //测试深度缓存
glShadeModel (GL_FLAT); //GL_FLAT填色模式
glClearColor(0.0, 0.0, 0.0, 0.0); //指定glClear清颜色缓冲区时用黑色,RGBA值在[0,1]内
glClearAccum(0.0, 0.0, 0.0, 0.0); //指定glClear清蒙板缓冲区时用黑色,RGBA值在[-1,1]内
}
void displayObjects(void)
{
GLfloat torus_diffuse[] = { 0.7, 0.7, 0.0, 1.0 };
GLfloat cube_diffuse[] = { 0.0, 0.7, 0.7, 1.0 };
GLfloat sphere_diffuse[] = { 0.7, 0.0, 0.7, 1.0 };
GLfloat octa_diffuse[] = { 0.7, 0.4, 0.4, 1.0 };
glPushMatrix (); //函数,允许对当前矩阵的改变
glTranslatef (0.0, 0.0, -5.0); //坐标转换
glRotatef (30.0, 1.0, 0.0, 0.0); //辅助库函数
glPushMatrix ();
glTranslatef (-0.80, 0.35, 0.0);
glRotatef (100.0, 1.0, 0.0, 0.0);
glMaterialfv(GL_FRONT, GL_DIFFUSE, torus_diffuse);
glutSolidTorus (0.275, 0.85, 16, 16);
glPopMatrix ();
glPushMatrix ();
glTranslatef (-0.75, -0.50, 0.0);
glRotatef (45.0, 0.0, 0.0, 1.0);
glRotatef (45.0, 1.0, 0.0, 0.0);
glMaterialfv(GL_FRONT, GL_DIFFUSE, cube_diffuse);
glutSolidCube (1.5); //// 原点的参考位置
glPopMatrix ();
glPushMatrix ();
glTranslatef (0.75, 0.60, 0.0);
glRotatef (30.0, 1.0, 0.0, 0.0);
glMaterialfv(GL_FRONT, GL_DIFFUSE, sphere_diffuse);
glutSolidSphere (1.0, 16, 16);
glPopMatrix ();
glPushMatrix ();
glTranslatef (0.70, -0.90, 0.25);
glMaterialfv(GL_FRONT, GL_DIFFUSE, octa_diffuse);
glutSolidOctahedron ();
glPopMatrix ();
glPopMatrix ();
}
#define ACSIZE 8
void display(void)
{
GLint viewport[4];
int jitter;
glGetIntegerv (GL_VIEWPORT, viewport);
glClear(GL_ACCUM_BUFFER_BIT); //// 累积缓冲
for (jitter = 0; jitter < ACSIZE; jitter++) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //添加绘图代码
accPerspective (50.0,
(GLdouble) viewport[2]/(GLdouble) viewport[3],
1.0, 15.0, j8[jitter].x, j8[jitter].y, 0.0, 0.0, 1.0);
displayObjects ();
glAccum(GL_ACCUM, 1.0/ACSIZE);
}
glAccum (GL_RETURN, 1.0); //将累积缓存里面的数据发送给颜色缓存
glFlush();
}
void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei) w, (GLsizei) h);
}
void keyboard(unsigned char key, int x, int y)
{
switch (key) {
case 27:
exit(0);
break;
}
}
/* Main Loop
* Be certain you request an accumulation buffer.
*/
int main(int argc, char** argv)
{
glutInit(&argc, argv); //初始GLUT并处理命令行的参数
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB
| GLUT_ACCUM | GLUT_DEPTH);
glutInitWindowSize (250, 250); //定义窗口大小
glutInitWindowPosition (100, 100); //窗口左上角在(100,100)
glutCreateWindow (argv[0]); //调用OpenGL初始化函数
init(); //注册OpenGL绘图函数
glutReshapeFunc(reshape); //注册键盘响应函数
glutDisplayFunc(display); //注册窗口大小改变时的响应函数
glutKeyboardFunc(keyboard); //进入GLUT消息循环，开始执行程序
glutMainLoop();
return 0;
}
