【求助】在OPENGL中实现三维纹理映射，自动生成坐标未完全成功

首先，从网上和红宝书书上找了些代码。凭自己的那点小经验改了改，希望能做一个颜色的立方体。即X、Y、Z各个轴分别代表RGB分量。

以下是没有使用自动生成纹理坐标的方式写的，效果还不错。

#define GLUT_DISABLE_ATEXIT_HACK

#include <stdlib.h>
#include <stdio.h>
#include <gl/glew.h>
#include <GL/glut.h>

#ifdef GL_VERSION_1_2
#define iWidth 16
#define iHeight 16
#define iDepth 16

static GLubyte image[iDepth][iHeight][iWidth][3];
static GLuint texName;
GLfloat angleX,angleY,angleZ;

/*  Create a 16x16x16x3 array with different color values in
*  each array element [r, g, b].  Values range from 0 to 255.
*/

void makeImage(void)
{
 int s, t, r;

 for (s = 0; s < 16; s++)
  for (t = 0; t < 16; t++)
   for (r = 0; r < 16; r++) {
    image[r][t][s][0] = (GLubyte) (s * 17);
    image[r][t][s][1] = (GLubyte) (t * 17);
    image[r][t][s][2] = (GLubyte) (r * 17);
   }
}

void init(void)
{   
 glClearColor (0.0, 0.0, 0.0, 0.0);
 glShadeModel(GL_FLAT);
 glEnable(GL_DEPTH_TEST);

 makeImage();
 glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

 glGenTextures(1, &texName);
 glBindTexture(GL_TEXTURE_3D, texName);
 glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S, GL_CLAMP);
 glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T, GL_CLAMP);
 glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R, GL_CLAMP);
 glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER,
  GL_NEAREST);
 glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER,
  GL_NEAREST);
 glTexImage3D(GL_TEXTURE_3D, 0, GL_RGB, iWidth, iHeight,
  iDepth, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
 glEnable(GL_TEXTURE_3D);
 angleX = 0.0;
 angleY = 0.0;
 angleZ = 0.0;
}

void display(void)
{
 int i;
 glPushMatrix();
 glTranslatef(1.0,0.0,-1.0);
 glRotatef(angleX,1.0,0.0,0.0);
 glRotatef(angleY,0.0,1.0,0.0);
 glRotatef(angleZ,0.0,0.0,1.0);

 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 glBegin(GL_QUADS);
 for(i = 0; i < 100; i ++)
 {
  glTexCoord3f(0.0, 0.0, (GLfloat)i * 0.01); glVertex3f(-2.25, -1.0, (GLfloat)i * 0.01);
  glTexCoord3f(0.0, 1.0, (GLfloat)i * 0.01); glVertex3f(-2.25, 1.0, (GLfloat)i * 0.01);
  glTexCoord3f(1.0, 1.0, (GLfloat)i * 0.01); glVertex3f(-0.25, 1.0, (GLfloat)i * 0.01);
  glTexCoord3f(1.0, 0.0, (GLfloat)i * 0.01); glVertex3f(-0.25, -1.0, (GLfloat)i * 0.01);

 }
 glEnd();
 glPopMatrix();
 glFlush();
}

void reshape(int w, int h)
{
 glViewport(0, 0, (GLsizei) w, (GLsizei) h);
 glMatrixMode(GL_PROJECTION);
 glLoadIdentity();
 gluPerspective(60.0, (GLfloat) w/(GLfloat) h, 1.0, 30.0);
 glMatrixMode(GL_MODELVIEW);
 glLoadIdentity();
 glTranslatef(0.0, 0.0, -4.0);
}

void keyboard(unsigned char key, int x, int y)
{
 switch (key) {
  case 's':
  case 'S':
   angleX +=15.0;
   glutPostRedisplay();
   break;
  case 'd':
  case 'D':
   angleY += 15.0;
   glutPostRedisplay();
   break;
  case 'f':
  case 'F':
   angleZ += 15.0;
   glutPostRedisplay();
   break;
  case 27:
   exit(0);
   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]);
 glewInit();
 init();
 glutReshapeFunc(reshape);
 glutDisplayFunc(display);
 glutKeyboardFunc (keyboard);
 glutMainLoop();
 return 0;
}
#else
int main(int argc, char** argv)
{
 fprintf (stderr, "This program demonstrates a feature which is not in OpenGL Version 1.0 or 1.1.\n");
 fprintf (stderr, "If your implementation of OpenGL has the right extensions,\n");
 fprintf (stderr, "you may be able to modify this program to make it run.\n");
 return 0;
}
#endif

效果图：两个不同的角度。

    

然后，我想把它改成自动生成三维纹理坐标的，但是没有成功。

主要修改的代码有两处：初始化函数Init()和绘制函数Display()

程序代码如下:

#define GLUT_DISABLE_ATEXIT_HACK

#include <stdlib.h>
#include <stdio.h>
#include <gl/glew.h>
#include <GL/glut.h>

#ifdef GL_VERSION_1_2
#define iWidth 16
#define iHeight 16
#define iDepth 16

static GLubyte image[iDepth][iHeight][iWidth][3];
static GLuint texName;
GLfloat angleX,angleY,angleZ;
GLfloat xPlane[] = {1.0,0.0,0.0,0.0};
GLfloat yPlane[] = {0.0,1.0,0.0,0.0};
GLfloat zPlane[] = {0.0,0.0,1.0,0.0};
float mat[16];

/*  Create a 16x16x16x3 array with different color values in
*  each array element [r, g, b].  Values range from 0 to 255.
*/

void makeImage(void)
{
 int s, t, r;

 for (s = 0; s < 16; s++)
  for (t = 0; t < 16; t++)
   for (r = 0; r < 16; r++) {
    image[r][t][s][0] = (GLubyte) (s * 17);
    image[r][t][s][1] = (GLubyte) (t * 17);
    image[r][t][s][2] = (GLubyte) (r * 17);
   }
}

void init(void)
{   
 glClearColor (0.0, 0.0, 0.0, 0.0);
 glShadeModel(GL_FLAT);
 glEnable(GL_DEPTH_TEST);

 makeImage();
 glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

 glGenTextures(1, &texName);
 glBindTexture(GL_TEXTURE_3D, texName);
 glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
 glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER,
  GL_LINEAR);
 glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER,
  GL_LINEAR);

 glTexGeni(GL_S,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);
 glTexGeni(GL_T,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);
 glTexGeni(GL_R,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);
 glTexGenfv(GL_S,GL_OBJECT_PLANE,xPlane);
 glTexGenfv(GL_T,GL_OBJECT_PLANE,yPlane);
 glTexGenfv(GL_R,GL_OBJECT_PLANE,zPlane);

 glTexImage3D(GL_TEXTURE_3D, 0, GL_RGB, iWidth, iHeight,
  iDepth, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
 glEnable(GL_TEXTURE_GEN_S);
 glEnable(GL_TEXTURE_GEN_T);
 glEnable(GL_TEXTURE_GEN_R);

 glEnable(GL_TEXTURE_3D);
 glLoadIdentity();

 angleX = 0.0;
 angleY = 0.0;
 angleZ = 0.0;
}

void display(void)
{
 int i;
 glPushMatrix();
 glTranslatef(0.0,0.0,-1.0);
 glRotatef(angleX,1.0,0.0,0.0);
 glRotatef(angleY,0.0,1.0,0.0);
 glRotatef(angleZ,0.0,0.0,1.0);

 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

 for (int ii=0;ii<160;ii++){
  glPushMatrix();
  glTranslatef(0.0f,0.0f,-1.0f +(float)ii*2.0f/(float)(160-1));
  glRectf(-1.0,-1.0,1.0,1.0);
  glPopMatrix();
 }

 glPopMatrix();
 glFlush();
}

void reshape(int w, int h)
{
 glViewport(0, 0, (GLsizei) w, (GLsizei) h);
 glMatrixMode(GL_PROJECTION);
 glLoadIdentity();
 gluPerspective(60.0, (GLfloat) w/(GLfloat) h, 1.0, 30.0);
 glMatrixMode(GL_MODELVIEW);
 glLoadIdentity();
 glTranslatef(0.0, 0.0, -4.0);
}

void keyboard(unsigned char key, int x, int y)
{
 switch (key) {
  case 's':
  case 'S':
   angleX +=15.0;
   glutPostRedisplay();
   break;
  case 'd':
  case 'D':
   angleY += 15.0;
   glutPostRedisplay();
   break;
  case 'f':
  case 'F':
   angleZ += 15.0;
   glutPostRedisplay();
   break;
  case 27:
   exit(0);
   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]);
 glewInit();
 init();
 glutReshapeFunc(reshape);
 glutDisplayFunc(display);
 glutKeyboardFunc (keyboard);
 glutMainLoop();
 return 0;
}
#else
int main(int argc, char** argv)
{
 fprintf (stderr, "This program demonstrates a feature which is not in OpenGL Version 1.0 or 1.1.\n");
 fprintf (stderr, "If your implementation of OpenGL has the right extensions,\n");
 fprintf (stderr, "you may be able to modify this program to make it run.\n");
 return 0;
}
#endif

所得到的结果：

        

 

貌似改成自动生成之后，和预想的结果差别挺大的。不知道是为什么。好像颜色变化不像原来那样是渐变的了，颜色的跳跃很明显。希望高手指点我一下，谢谢。