openGL 灯光与材质例子. 顺带完成了一个颇复杂的平面分级算法, 修正版,列出了所有易错的地方:

 1. 开启了 GL_XXX_ARRAY 后一定要使用对应的pointer, 否则就把 GL_XXX_ARRAY disable 掉.

 2. 法线不一定要设置, openGL会自动为每一Vertex生成一个默认的, 自己设置当然可控性更好.

 3. initLights() 等GL具体到场景内容的设置必须放在 GLUT 基本设置之后(一开始就死在这个弱智的问题).

 4. 灯光的 GL_POSITION, 齐次坐标最后一位如果是 0, 则为平行光, 无需设置 GL_SPOT_DIRECTION 和 GL_SPOT_CUTOFF(这个值为照射角的一半). 如果是1, 则为聚光灯.

 5. GL 环境光对所有面都会有影响.尝试变换灯光的颜色和环境光颜色的数组值,观察其变化. 

 6. 材质的 SHINESS 参数, 1 端接近橡胶与织物, 128 端接近金属与清漆. 

  7. 灯灯灯凳~ 最麻烦的还是平面分级算法, 理论上分级越细, 关照效果越细致, 代码如下:

#include <gl/GLUT.h>
#include <stdio.h>


static GLfloat LEVEL=12;
static GLfloat LENGTH=2;
static GLfloat START_PT=-1*(LENGTH/2);
static GLfloat END_PT=1*(LENGTH/2);


GLfloat angle=0;

GLfloat *vertices;
//GLfloat *colors;
short *indices;
GLfloat *normals;

//GLfloat vertices[]={-1,-1,1,
//					-0.3333f,-1,1,
//					0.3333f,-1,1,
//					1,-1,1,
//					-1,-0.3333,1,
//					-0.3333f,-0.3333,1,
//					0.3333f,-0.3333,1,
//					1,-0.3333,1,
//					-1,0.3333,1,
//					-0.3333f,0.3333,1,
//					0.3333f,0.3333,1,
//					1,0.3333,1,
//					-1,1,1,
//					-0.3333f,1,1,
//					0.3333f,1,1,
//					1,1,1};

//short indices[]={0,1,4, 1,5,4, 1,2,5, 2,6,5, 2,3,6, 3,7,6,
//				4,5,8, 5,9,8, 5,6,9, 6,10,9, 6,7,10, 7,11,10,
//				8,9,12, 9,13,12, 9,10,13, 10,14,13, 10,11,14, 11,15,14};



//lights
GLfloat lightPos[]={0,0,2.5f,1};
GLfloat lightColor[]={0.6f,0.3f,0.3f,1};		//red
GLfloat lightDir[]={0,0,-1};

//ambient light
GLfloat light_ambient[]={0.3f,0.3f,0.4f,1};		//light blue


//materials
GLfloat cubeColor[]={0.6f,0.6f,0.6f,1};		//gray color
GLfloat cubeSpecular[]={1,1,1,1};


void setMaterial(){
	glMaterialfv(GL_FRONT_AND_BACK,GL_AMBIENT_AND_DIFFUSE,cubeColor);
	glMaterialfv(GL_FRONT_AND_BACK,GL_SPECULAR,cubeSpecular);
	//try to change the shiness from 1(rubber/frabic)-128(metal/clear painted)
	glMaterialf(GL_FRONT_AND_BACK,GL_SHININESS,20);
}


void drawPlane(){

	glVertexPointer(3,GL_FLOAT,0,vertices);
	//glNormalPointer(GL_FLOAT,0,normals);
	//glColorPointer(4,GL_FLOAT,0,colors);
	glDrawElements(GL_TRIANGLES,(GLsizei)((LEVEL-1)*(LEVEL-1)*2*3),GL_UNSIGNED_SHORT,indices);
}






void drawCube(){

	//set material
	setMaterial();


	glPushMatrix();
		drawPlane();
	glPopMatrix();

	glPushMatrix();
		glRotatef(-90,1,0,0);
		drawPlane();
	glPopMatrix();

	glPushMatrix();
		glRotatef(90,1,0,0);
		drawPlane();
	glPopMatrix();

	glPushMatrix();
		glRotatef(180,1,0,0);
		drawPlane();
	glPopMatrix();

	glPushMatrix();
		glRotatef(90,0,1,0);
		drawPlane();
	glPopMatrix();

	glPushMatrix();
		glRotatef(-90,0,1,0);
		drawPlane();
	glPopMatrix();
}


void rendering(void){

	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

	glPushMatrix();
		glRotatef(angle,0,1,0);
		drawCube();
	glPopMatrix();

	glutSwapBuffers();

	angle+=0.01;

}

void reshape(int w, int h){

	if(h==0){
		h=1;
	}

	GLfloat ratio=(GLfloat)(w/h);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glViewport(0,0,w,h);
	gluPerspective(45,ratio,0.1,1000);
	gluLookAt(0,5,10,0,0,0,0,1,0);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();


}

void makeArrays(){
	
	//build vertices array for one face
	GLfloat step=(GLfloat)(LENGTH/(LEVEL-1));
	GLint total=LEVEL*LEVEL*3;
	GLint oneLine=LEVEL*3;	//12

	//printf("level: %f  ", step);

	vertices=new GLfloat[total];
	
	for(int i=0;i<LEVEL;i++){
		//every point x,y,z
		for(int j=0;j<LEVEL*3;j+=3){
			vertices[(i*oneLine)+j]=(GLfloat)(START_PT+(j*step/3));
			vertices[(i*oneLine)+(j+1)]=(GLfloat)(START_PT+i*step);
			vertices[(i*oneLine)+(j+2)]=(GLfloat)(LENGTH/2);

			printf("pt : x: %f, y: %f, z: %f  \n", 
				vertices[(i*oneLine)+j],
				vertices[(i*oneLine)+j+1],
				vertices[(i*oneLine)+j+2]);
		}
	}



	//build colors array, normal white color;
	/*GLint totalColor=LEVEL*LEVEL*4;
	colors=new GLfloat[totalColor];

	for(int r=0;r<totalColor;r+=4){
		colors[r]=1;
		colors[r+1]=1;
		colors[r+2]=1;
		colors[r+3]=1;
	}*/



	//build index array for one face
	//using TRIANGLES

	indices=new short[(LEVEL-1)*(LEVEL-1)*2*3];		//square of LEVEL-1, 2 triangles, 3 points;

	for(int m=0;m<LEVEL-1;m++){

		for(int n=0;n<LEVEL-1;n++){

			indices[m*((GLint)LEVEL-1)*6+n*6+0]=n+m*((GLint)LEVEL-1)+m+0;
			indices[m*((GLint)LEVEL-1)*6+n*6+1]=n+m*((GLint)LEVEL-1)+m+1;
			indices[m*((GLint)LEVEL-1)*6+n*6+2]=n+m*((GLint)LEVEL-1)+m+(LEVEL);
			indices[m*((GLint)LEVEL-1)*6+n*6+3]=n+m*((GLint)LEVEL-1)+m+1;
			indices[m*((GLint)LEVEL-1)*6+n*6+4]=n+m*((GLint)LEVEL-1)+m+(LEVEL)+1;
			indices[m*((GLint)LEVEL-1)*6+n*6+5]=n+m*((GLint)LEVEL-1)+m+(LEVEL);
		}
	}


	normals=new GLfloat[LEVEL*LEVEL*3];

	for(int s=0;s<LEVEL*LEVEL*3;s+=3){
		normals[s]=0;
		normals[s+1]=0;
		normals[s+2]=1;
	}
			
			
}


void initLights(){

	glEnable(GL_LIGHTING);

	glEnable(GL_LIGHT0);
	glLightfv(GL_LIGHT0,GL_POSITION,lightPos);
	glLightfv(GL_LIGHT0,GL_AMBIENT,lightColor);
	glLightfv(GL_LIGHT0,GL_DIFFUSE,lightColor);
	glLightfv(GL_LIGHT0,GL_SPECULAR,lightColor);
	glLightfv(GL_LIGHT0,GL_SPOT_DIRECTION,lightDir);
	glLightf(GL_LIGHT0,GL_SPOT_CUTOFF,45);
	
	//
	glLightModelfv(GL_LIGHT_MODEL_AMBIENT,light_ambient);


}


int main(int argc, char* args[]){

	//make arrays
	makeArrays();
	
	//basic init
	glutInit(&argc,args);
	glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);
	
	//window init
	glutInitWindowPosition(100,100);
	glutInitWindowSize(600,600);
	glutCreateWindow("light cube");

	//functions init
	glutDisplayFunc(rendering);
	glutIdleFunc(rendering);
	glutReshapeFunc(reshape);

	//gl init
	glEnable(GL_DEPTH_TEST);
	glEnableClientState(GL_VERTEX_ARRAY);
	//glEnableClientState(GL_NORMAL_ARRAY);
	//glEnableClientState(GL_COLOR_ARRAY);

	glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);

	//init lights
	initLights();
	
	//run main loop, trigger all the funtions
	glutMainLoop();

	return 0;
}