opengl: 编程指南例子解析 opengl_wrap

#include <iostream>

using namespace std;
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>

#define checkImageWidth 64  //图片宽度
#define checkImageHeight 64 //图片高度

static GLubyte checkImage[checkImageWidth][checkImageHeight][4];//定义图片，RBGA

//生成黑白相间的图片
void makeCheckImage(void)
{
int i, j, c;

for (i = 0; i < checkImageHeight; i++) {
for (j = 0; j < checkImageWidth; j++) {
c = ((((i&0x8)==0)^((j&0x8))==0))*255;
checkImage[i][j][0] = (GLubyte) c;
checkImage[i][j][1] = (GLubyte) c;
checkImage[i][j][2] = (GLubyte) c;
checkImage[i][j][3] = (GLubyte) 255;
}
}
}

void init(void)
{
//清空用黑色
glClearColor(0.0, 0.0, 0.0, 0.0);
//平滑着色
glShadeModel(GL_FLAT);
//启用深度缓存
glEnable(GL_DEPTH_TEST);

makeCheckImage();
//设置纹理图片封包解包的对其方式，1字节对齐， 即每行存储的字节数必须是1的整数倍
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

//s，t方向超过1纹理重复
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

//当所显示的纹理比加载进来的纹理大或小时，采用GL_NEAREST的方法来处理
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

//载入二维纹理图像
glTexImage2D(GL_TEXTURE_2D, 0, 4, checkImageWidth, checkImageHeight,
0, GL_RGBA, GL_UNSIGNED_BYTE, checkImage);
}

void reshape(int w, int h)
{
//设置视口大小
glViewport(0, 0, (GLsizei) w, (GLsizei) h);
//载入投影矩阵
glMatrixMode(GL_PROJECTION);
//当前矩阵单位化
glLoadIdentity();
//设置透视投影
gluPerspective(60.0, (GLfloat) w/(GLfloat) h, 1.0, 30.0);
//载入模型矩阵
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
//摄像机在原点，把模型向z轴平移 3.6，不然看不到或看不全。
glTranslatef(0.0, 0.0, -3.6);
}

void display(void)
{
//清除深度缓存，颜色缓存
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//启用2d纹理
glEnable(GL_TEXTURE_2D);
//设置纹理和材料颜色混合
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);

//画两个面
glBegin(GL_QUADS);
glTexCoord2f(0.0, 0.0); glVertex3f(-2.0, -1.0, 0.0);
glTexCoord2f(0.0, 5.0); glVertex3f(-2.0, 1.0, 0.0);
glTexCoord2f(5.0, 5.0); glVertex3f(0.0, 1.0, 0.0);
glTexCoord2f(5.0, 0.0); glVertex3f(0.0, -1.0, 0.0);

glTexCoord2f(0.0, 0.0); glVertex3f(1.0, -1.0, 0.0);
glTexCoord2f(0.0, 1.0); glVertex3f(1.0, 1.0, 0.0);
glTexCoord2f(1.0, 1.0); glVertex3f(2.41421, 1.0, -1.41421);
glTexCoord2f(1.0, 0.0); glVertex3f(2.41421, -1.0, -1.41421);
glEnd();
glFlush();
glDisable(GL_TEXTURE_2D);

}

void keyboard (unsigned char key, int x, int y)
{
//设置纹理滤波
switch (key) {
case 's':
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glutPostRedisplay();
break;
case 'S':
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glutPostRedisplay();
break;
case 't':
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glutPostRedisplay();
break;
case 'T':
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glutPostRedisplay();
break;

case 'a':
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glutPostRedisplay();
break;
case 'A':
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glutPostRedisplay();
break;

case 'e':
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glutPostRedisplay();
break;

case 'E':
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glutPostRedisplay();
break;

case 27:
exit(0);
break;
default:
break;
}
}

int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(250, 250);
glutInitWindowPosition(100, 100);
glutCreateWindow(argv[0]);
init();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard);
glutMainLoop();
return 0;
}