第8讲-使用光照及材质.doc

　　使用了光照和材质可以使物体更逼真，具有立体感。例4就是没有使用光照使呈现在我们眼前的物体茶壶和立方体没有立体感。

　　例6：绘制三个使用不同材质的球体。
#include <windows.h>
#include <GL/glut.h>
GLfloat light_position[] = {0.0,3.0,6.0,0.0};
GLfloat no_mat[] = {0.0,0.0,0.0,1.0};
GLfloat mat_grey_ambient[] = {0.5,0.5,0.5,1.0};
GLfloat mat_red_ambient[] = {0.0,0.0,1.0,1.0};
GLfloat mat_diffuse[] = {0.8,0.2,0.5,1.0};
GLfloat mat_specular[] = {1.0,1.0,1.0,1.0};
GLfloat no_shininess[] = {0.0};
GLfloat low_shininess[] = {5.0};
GLfloat high_shininess[] = {100.0};
GLfloat mat_emission[] = {0.3,0.2,0.2,0.0};

void myInit(void)
{
　glLightfv(GL_LIGHT2,GL_POSITION,light_position);//设置光源

　glEnable(GL_DEPTH_TEST);
　glDepthFunc(GL_LESS);//指定深度比较中使用的数值
　glEnable(GL_LIGHTING);
　glEnable(GL_LIGHT0);
　glShadeModel(GL_SMOOTH);
}

void display(void)
{
　glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
　glPushMatrix();
　/*为光照模型指定材质参数*/
　glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse);
　glMaterialfv(GL_FRONT,GL_SPECULAR,mat_specular);
　glMaterialfv(GL_FRONT,GL_SHININESS,high_shininess);
　glMaterialfv(GL_FRONT,GL_EMISSION,no_mat);

　glColorMaterial(GL_FRONT,GL_AMBIENT);//使材质色跟踪当前颜色
　glEnable(GL_COLOR_MATERIAL);

　/*第一个球形*/
　glPushMatrix();
　glColor3fv(no_mat);
　glTranslatef(-2.5,1.5,0.0);
　glRotatef(15.0,1.0,0.0,0.0);
　glutSolidSphere(1.2,20.0,20.0);
　glPopMatrix();

　/*第二个球形*/
　glPushMatrix();
　glColor3fv(mat_grey_ambient);
　glRotatef(15.0,1.0,0.0,0.0);
　glutSolidSphere(1.2,20.0,20.0);
　glPopMatrix();

　/*第三个球形*/
　glPushMatrix();
　glColor3fv(mat_red_ambient);
　glTranslatef(2.5,-1.5,0.0);
　glRotatef(15.0,1.0,0.0,0.0);
　glutSolidSphere(1.2,20.0,20.0);
　glPopMatrix();

　glDisable(GL_COLOR_MATERIAL);
　glPopMatrix();

　glFlush();
}

void myReshape(int w,int h)
{
　glViewport(0,0,(GLsizei)w,(GLsizei)h);
　glMatrixMode(GL_PROJECTION);
　glLoadIdentity();

　if(w <= h)
　　glOrtho(-5.5,5.5,-5.5*(GLfloat)h/(GLfloat)w,5.5*(GLfloat)h/(GLfloat)w,-5.5,5.5);
　else
　　glOrtho(-5.5*(GLfloat)w/(GLfloat)h,5.5*(GLfloat)w/(GLfloat)h,-5.5,5.5,-5.5,5.5);

　glMatrixMode(GL_MODELVIEW);
　glLoadIdentity();
}

int main(int argc,char ** argv)
{
　/*初始化*/
　glutInit(&argc,argv);
　glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
　glutInitWindowSize(400,400);
　glutInitWindowPosition(100,100);

　/*创建窗口*/
　glutCreateWindow(" Light&Material ");

　/*绘制与显示*/
　myInit();
　glutReshapeFunc(myReshape);
　glutDisplayFunc(display);

　glutMainLoop();
　return 0;
}

　　函数myInit中：

　　·glLight设置光源的参数。有三个参数，第一个参数指定光照的数目，最大为8。第二个参数为光照的单值光源参数。第三个参数为赋给第二个参数的值，本例中即为将light_position的值赋值给GL_POSITION。

　　display函数中：

　　·glMaterial为光照模型指定材质参数。第一个参数为改变材质的面，其值必为GL_FRONT, GL_BACK或GL_FRONT_AND_BACK中的一个。第二个参数为需要改变的材质参数。第三个参数为赋给参数二的值或指向值的指针。本例中均为指针。

　　·glColorMateria使材质色跟踪当前颜色。第一个参数指定哪一个面需要使材质色跟踪当前颜色。第二个参数指定哪个参数需要跟踪颜色。