Opengl立方体灯不正确

我编写了一个显示立方体的OpenGL程序。

但是光线不正确，因为当我旋转立方体时，并非所有面部都被正确点亮：有两个面部呈现黑色。



这是代码：

I wrote a OpenGL program that shows a cube.
But the light is not correct because when I rotate the cube, not all the faces are correctly lighted: there are two faces that appears black.

Here's the code:

#include<GL\glut.h><br />
#include<GL\GL.h>º<br />
<br />
float rotX = 0.0, rotY = 0.0;<br />
<br />
void light ()<br />
{<br />
	static float Position [] = {0.0, 0.0, 1.0, 0.0};<br />
	static float Diffuse  [] = {0.8, 0.8, 0.8, 1.0};<br />
	static float Ambient  [] = {0.3, 0.3, 0.3, 1.0};<br />
	static float Specular [] = {1.0, 1.0, 1.0, 1.0};<br />
<br />
	glLightfv(GL_LIGHT0, GL_POSITION, Position);<br />
	glLightfv(GL_LIGHT0, GL_DIFFUSE,  Diffuse);<br />
	glLightfv(GL_LIGHT0, GL_AMBIENT,  Ambient);<br />
	glLightfv(GL_LIGHT0, GL_SPECULAR, Specular);<br />
<br />
	glEnable(GL_LIGHTING);<br />
	glEnable(GL_LIGHT0);<br />
}<br />
<br />
void drawCube(void)<br />
{<br />
	int i;<br />
<br />
	GLfloat n[6][3] = {  /* Normals for the 6 faces of a cube. */<br />
	{-1.0, 0.0, 0.0}, {0.0, 1.0, 0.0}, {1.0, 0.0, 0.0},<br />
	{0.0, -1.0, 0.0}, {0.0, 0.0, 1.0}, {0.0, 0.0, -1.0} };<br />
	<br />
	GLint faces[6][4] = {  /* Vertex indices for the 6 faces of a cube. */<br />
	{0, 1, 2, 3}, {3, 2, 6, 7}, {7, 6, 5, 4},<br />
	{4, 5, 1, 0}, {5, 6, 2, 1}, {7, 4, 0, 3} };<br />
	<br />
	GLfloat v[8][3];  /* Will be filled in with X,Y,Z vertexes. */<br />
<br />
	v[0][0] = v[1][0] = v[2][0] = v[3][0] = -1;<br />
	v[4][0] = v[5][0] = v[6][0] = v[7][0] = 1;<br />
	v[0][1] = v[1][1] = v[4][1] = v[5][1] = -1;<br />
	v[2][1] = v[3][1] = v[6][1] = v[7][1] = 1;<br />
	v[0][2] = v[3][2] = v[4][2] = v[7][2] = 1;<br />
	v[1][2] = v[2][2] = v[5][2] = v[6][2] = -1;<br />
<br />
	for (i = 0; i < 6; i++) {<br />
		glBegin(GL_QUADS);<br />
			glNormal3fv(&n[i][0]);<br />
			glVertex3fv(&v[faces[i][0]][0]);<br />
			glVertex3fv(&v[faces[i][1]][0]);<br />
			glVertex3fv(&v[faces[i][2]][0]);<br />
			glVertex3fv(&v[faces[i][3]][0]);<br />
		glEnd();<br />
	}<br />
}<br />
<br />
void display ()<br />
{<br />
	glClear(GL_COLOR_BUFFER_BIT);<br />
	glClear(GL_DEPTH_BUFFER_BIT);<br />
		<br />
	glMatrixMode(GL_MODELVIEW);<br />
	glLoadIdentity();<br />
<br />
	float diffuse [] = {1.0, 1.0, 0.0};<br />
	glMaterialfv (GL_FRONT, GL_DIFFUSE, diffuse);<br />
	<br />
	glTranslatef(0.0,0.0,-5.0);<br />
	glRotatef(rotX, 0.0, 1.0, 0.0);<br />
	glRotatef(rotY, 1.0, 0.0, 0.0);<br />
	<br />
	drawCube();<br />
<br />
	glFlush();<br />
}<br />
<br />
void reshape (int w, int h)<br />
{<br />
	float aspect = (float)w/(float)h;<br />
	<br />
	glViewport(0, 0, w, h);<br />
<br />
	glMatrixMode(GL_PROJECTION);<br />
	glLoadIdentity();<br />
<br />
	gluPerspective(60.0, aspect, 0.1, 10.0);<br />
}<br />
<br />
void special (int key, int, int)<br />
{<br />
	switch (key)<br />
	{<br />
	case GLUT_KEY_UP:		rotY -= 1.0; break;<br />
	case GLUT_KEY_DOWN:		rotY += 1.0; break;<br />
	case GLUT_KEY_LEFT:		rotX -= 1.0; break;<br />
	case GLUT_KEY_RIGHT:	rotX += 1.0; break;<br />
	default: return;<br />
	}<br />
<br />
	glutPostRedisplay();<br />
}<br />
<br />
int main (int argc, char* argv [])<br />
{<br />
	glutInit(&argc, argv);<br />
	glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE|GLUT_DEPTH);<br />
	glutCreateWindow("Cube");<br />
	glutReshapeWindow(640,480);	<br />
<br />
	glutDisplayFunc(display);<br />
	glutReshapeFunc(reshape);<br />
	glutSpecialFunc(special);<br />
<br />
	glClearColor(0.0, 0.0, 0.0, 1.0);<br />
<br />
	light();<br />
	<br />
	glEnable(GL_DEPTH_TEST);<br />
	<br />
	glutMainLoop();<br />
<br />
	return 0;<br />
}

有人可以帮助我吗？



我尝试过：



我尝试纠正法线，然后从OpenGL读取CUBE.C教程。

Can someone help me?

What I have tried:

I tried to correct normals, and I read the CUBE.C tutorial from OpenGL.