紧接上一次，这回讲材质：OPENGL通过材料对R、G、B的近似反光率来近似定义材料颜色。也分为环境、漫反射、镜面反射成分。他们决定材料对环境光、漫反射光和镜面反射光的反射程度。将材料的特性与光源特性结合就是观察的最终显示效果。例如红色塑料球，大部分是红色，在光源形成的高光处，则出现光源的特性颜色。很EASY，不是么？材质的定义：void glMaterial{if}[v](GLenum face,GLenum pname,TYPE param);其中：face:可以是GL_FRONT、GL_BACK、GL_FRONT_AND_BACK,它表明当前材质应用到物体的哪一个表面上。pname说明特定材质属性（很类似上一次光源的定义）：pname 缺省值 说明GL_AMBIENT 0.2,0.2,0.2,1.0 材质的环境反射光GL_DIFFUSE 0.8,0.8,0.8,1.0 材质的漫反射光GL_AMBIENT_AND_DIFFUSE 材质的环境光和漫反射光颜色GL_SPECULAR 0.0,0.0.0.0,1.0 材质镜面反射光GL_SHINESS 0.0 镜面指数（光照度）GL_EMISSION 0.0,0.0,0.0,1.0 材质的辐射颜色GL_COLOR_INDEXES 0,1,1 材质的环境光、漫反射光和镜面反射光颜色请看下面材质的简单例子：#include <windows.h>#include <gl/gl.h>#include <gl/glu.h>#include <gl/glaux.h>#pragma comment(lib, "OpenGl32.lib")#pragma comment(lib, "glu32.lib")#pragma comment(lib, "glaux.lib")#pragma warning(disable : 4244)// MIPS#pragma warning(disable : 4136)// X86#pragma warning(disable : 4051)// ALPHA//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////sample.cppvoid myinit(void);void CALLBACK display(void);void CALLBACK reshape(GLsizei w,GLsizei h);void myinit(void){ auxInitDisplayMode(AUX_SINGLE|AUX_RGBA); auxInitPosition(0,0,500,500); auxInitWindow("sample1"); glClearColor(0.0,0.0,0.0,0.0); glClear(GL_COLOR_BUFFER_BIT);// glShadeModel(GL_FLAT);//首先定义一个材质，定义方法非常类似前面讲到的光源定义。 GLfloat mat_ambient[]={0.8,0.8,0.8,1.0};//定义 紫色 的漫反射特性 GLfloat mat_diffuse[]={0.8,0.0,0.8,1.0};//定义 亮紫色 的镜面反射特性 GLfloat mat_specular[]={1.0,0.0,1.0,1.0};//定义镜面反射的光亮度 GLfloat mat_shininess[]={50.0};//将以上材质定义应用 glMaterialfv(GL_FRONT,GL_AMBIENT,mat_ambient);glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse); glMaterialfv(GL_FRONT,GL_SPECULAR,mat_specular); glMaterialfv(GL_FRONT,GL_SHININESS,mat_shininess);//这里我们简化光源，以显示材质的效果。//这里我们只指定光源位置，其他默认：白色光源。//你也可以加入光源的定义，看看光源和材质的合成的效果//正是因为它们能够合成，才能产生比真实生活中多的多的效果，这也正是//3D技术吸引人的魅力所在。 GLfloat light_position[]={1.0,1.0,1.0,0.0}; glLightfv(GL_LIGHT0,GL_POSITION,light_position);// GLfloat light_diffuse[]={0.0,0.0,1.0,1.0};// glLightfv(GL_LIGHT0,GL_DIFFUSE,light_diffuse);//将光源设置应用 glEnable(GL_LIGHTING); glEnable(GL_LIGHT0);//着色消隐//*******其实说白乐，这就是大名鼎鼎的 Z-BUFFER 呀************// glDepthFunc(GL_LESS); glEnable(GL_DEPTH_TEST);}void CALLBACK reshape(GLsizei w,GLsizei h){glViewport(0,0,w,h);glMatrixMode(GL_PROJECTION);glLoadIdentity();if(w<=h)glOrtho(-2.0,2.0,-2.0*(GLfloat)h/(GLfloat)w,2.0*(GLfloat)h/(GLfloat)w,-10.0,10.0);elseglOrtho(-2.0*(GLfloat)h/(GLfloat)w,2.0*(GLfloat)h/(GLfloat)w,-2.0,2.0,-10.0,10.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();}void draw(void){auxSolidSphere(1.0);}void CALLBACK display(void){glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);glLoadIdentity();draw();glFlush();}void main(void){ myinit(); auxReshapeFunc(reshape); auxMainLoop(display);}//end of sample////////////////////////////////////////////////////通过以上的例子，我们会看到材质定义的实现和光源的效果是一样的，就我们日常的感觉，定义材质更加符合人们的习惯。而光源使用白光。这里我们看到的是一个紫色的球，其高光部分呈现亮紫色。作为比较，下面我们给出一个12个彩色球的例子，大家可以看出各种光源、材质应用的效果，在一起比较。给出例子之前，介绍两个函数：void glPushMatrix();void glPopMatrix();我前面已经讲过，所有几何投影变换都是矩阵相乘的结果。如果你希望保持一个初始坐标点，就要用到这两个重要函数：矩阵入栈和矩阵出栈。你可以这样理解，为了在左上角画一个球，你先保存当前矩阵，glPushMatrix()（入栈），然后把坐标平移到左上角，然后调用auxSolidSphere(1.0)，画一个半径1.0的球，这时再调用glPopMatrix()（矩阵出栈），就又回到原始坐标点，这时的球就在左上角乐。这个程序很长，但实际上，长的部分统统是重复画12个球的工作，所以也比较好理解。
#include <windows.h>#include <gl/gl.h>#include <gl/glu.h>#include <gl/glaux.h>#pragma comment(lib, "OpenGl32.lib")#pragma comment(lib, "glu32.lib")#pragma comment(lib, "glaux.lib")#pragma warning(disable : 4244)// MIPS#pragma warning(disable : 4136)// X86#pragma warning(disable : 4051)// ALPHA////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////sample.cppvoid myinit(void);void CALLBACK display(void);void CALLBACK reshape(GLsizei w,GLsizei h);void myinit(void){ auxInitDisplayMode(AUX_SINGLE|AUX_RGBA); auxInitPosition(0,0,500,500); auxInitWindow("sample1"); glClearColor(0.0,0.1,0.1,0.0); glClear(GL_COLOR_BUFFER_BIT);// glShadeModel(GL_FLAT);//首先定义光源 GLfloat light_ambient[]={0.0,0.0,0.0,1.0}; GLfloat light_diffuse[]={1.0,1.0,1.0,1.0}; GLfloat light_specular[]={1.0,1.0,1.0,1.0}; GLfloat light_position[]={0.0,3.0,2.0,0.0}; GLfloat Imodel_ambient[]={0.4,0.4,0.4,1.0};//应用光源 glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient); glLightfv(GL_LIGHT0, GL_POSITION, light_position); glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse); glEnable(GL_LIGHTING); glEnable(GL_LIGHT0);//初始化Z BUFFER glDepthFunc(GL_LESS); glEnable(GL_DEPTH_TEST);}void CALLBACK reshape(GLsizei w,GLsizei h){glViewport(0,0,w,h);glMatrixMode(GL_PROJECTION);glLoadIdentity();if(w<=h)glOrtho(-6.0,6.0,-6.0*(GLfloat)h/(GLfloat)w,6.0*(GLfloat)h/(GLfloat)w,-10.0,10.0);elseglOrtho(-6.0*(GLfloat)h/(GLfloat)w,6.0*(GLfloat)h/(GLfloat)w,-6.0,6.0,-10.0,10.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();}void draw(void){auxSolidSphere(1.0);}void CALLBACK display(void){ glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);//建立材质数据库 GLfloat no_mat[]={0.0,0.0,0.0,1.0}; GLfloat mat_ambient[]={0.7,0.7,0.7,1.0}; GLfloat mat_ambient_color[]={0.8,0.8,0.2,1.0}; GLfloat mat_diffuse[]={0.1,0.5,0.8,1.0}; 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};////////////////////////////////////////////////////////////1-1 仅有漫反射光，无环境光和镜面光 glPushMatrix(); glTranslatef(-3.75,3.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,no_mat); glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse); glMaterialfv(GL_FRONT,GL_SPECULAR,no_mat); glMaterialfv(GL_FRONT,GL_SHININESS,no_shininess); glMaterialfv(GL_FRONT,GL_EMISSION,no_mat); draw(); glPopMatrix();//1-2 有漫反射光，并且有低高光，无环境光 glPushMatrix(); glTranslatef(-1.25,3.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,no_mat); glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse); glMaterialfv(GL_FRONT,GL_SPECULAR,mat_specular); glMaterialfv(GL_FRONT,GL_SHININESS,low_shininess); glMaterialfv(GL_FRONT,GL_EMISSION,no_mat); draw(); glPopMatrix();//1-3 有漫反射光和镜面光，很亮的高光，无环境光 glPushMatrix(); glTranslatef(1.25,3.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,no_mat); 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); draw(); glPopMatrix();//1-4 有漫反射光和辐射光，无环境光和镜面反射光 glPushMatrix(); glTranslatef(3.75,3.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,no_mat); glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse); glMaterialfv(GL_FRONT,GL_SPECULAR,no_mat); glMaterialfv(GL_FRONT,GL_SHININESS,no_shininess); glMaterialfv(GL_FRONT,GL_EMISSION,mat_emission); draw(); glPopMatrix();////////////////////////////////////////////////////////////////2-1 有漫反射光和环境光，无镜面反射光 glPushMatrix(); glTranslatef(-3.75,0.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,mat_ambient); glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse); glMaterialfv(GL_FRONT,GL_SPECULAR,no_mat); glMaterialfv(GL_FRONT,GL_SHININESS,no_shininess); glMaterialfv(GL_FRONT,GL_EMISSION,no_mat); draw(); glPopMatrix();//2-2 有漫反射光、环境光和镜面光，而且有低高光 glPushMatrix(); glTranslatef(-1.25,0.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,mat_ambient); glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse); glMaterialfv(GL_FRONT,GL_SPECULAR,mat_specular); glMaterialfv(GL_FRONT,GL_SHININESS,low_shininess); glMaterialfv(GL_FRONT,GL_EMISSION,no_mat); draw(); glPopMatrix();//2-3 有漫反射光环境光和镜面光，而且有很亮的高光 glPushMatrix(); glTranslatef(1.25,0.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,mat_ambient); 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); draw(); glPopMatrix();//2-4有漫反射光、环境光和辐射光，无镜面光 glPushMatrix(); glTranslatef(3.75,0.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,mat_ambient); glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse); glMaterialfv(GL_FRONT,GL_SPECULAR,no_mat); glMaterialfv(GL_FRONT,GL_SHININESS,no_shininess); glMaterialfv(GL_FRONT,GL_EMISSION,mat_emission); draw(); glPopMatrix();/////////////////////////////////////////////////////////////////3-1 有漫反射光和有颜色的环境光，无镜面光 glPushMatrix(); glTranslatef(-3.75,-3.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,mat_ambient_color); glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse); glMaterialfv(GL_FRONT,GL_SPECULAR,no_mat); glMaterialfv(GL_FRONT,GL_SHININESS,no_shininess); glMaterialfv(GL_FRONT,GL_EMISSION,no_mat); draw(); glPopMatrix();//3-2有漫反射光和有颜色的环境光以及镜面光，且有低高光 glPushMatrix(); glTranslatef(-1.25,-3.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,mat_ambient_color); glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse); glMaterialfv(GL_FRONT,GL_SPECULAR,mat_specular); glMaterialfv(GL_FRONT,GL_SHININESS,low_shininess); glMaterialfv(GL_FRONT,GL_EMISSION,no_mat); draw(); glPopMatrix();//3-3 有漫反射光和有颜色的环境光以及镜面光，且有很亮的高光 glPushMatrix(); glTranslatef(1.25,-3.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,mat_ambient_color); 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); draw(); glPopMatrix();//3-4 有漫反射光和有颜色的环境光以及辐射光，无镜面光 glPushMatrix(); glTranslatef(3.75,-3.0,0.0); glMaterialfv(GL_FRONT,GL_AMBIENT,mat_ambient_color); glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse); glMaterialfv(GL_FRONT,GL_SPECULAR,no_mat); glMaterialfv(GL_FRONT,GL_SHININESS,no_shininess); glMaterialfv(GL_FRONT,GL_EMISSION,mat_emission); draw(); glPopMatrix(); glFlush();}void main(void){ myinit(); auxReshapeFunc(reshape); auxMainLoop(display);}//end of sample////////////////////////////////////////////////////
