openGL下版本问题－－glTexImage3D
红皮书上例子程序：
#include <GL/glut.h>
#include <GL/glext.h>
#include <stdlib.h>
#include <stdio.h>
#ifdef GL_VERSION_1_2
#defineiWidth 16
#defineiHeight 16
#define iDepth 16
static GLubyte image[iDepth][iHeight][iWidth][3];
static GLuint texName;
/* 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);
}
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glBegin(GL_QUADS);
glTexCoord3f(0.0, 0.0, 0.0); glVertex3f(-2.25, -1.0, 0.0);
glTexCoord3f(0.0, 1.0, 0.0); glVertex3f(-2.25, 1.0, 0.0);
glTexCoord3f(1.0, 1.0, 1.0); glVertex3f(-0.25, 1.0, 0.0);
glTexCoord3f(1.0, 0.0, 1.0); glVertex3f(-0.25, -1.0, 0.0);
glTexCoord3f(0.0, 0.0, 1.0); glVertex3f(0.25, -1.0, 0.0);
glTexCoord3f(0.0, 1.0, 1.0); glVertex3f(0.25, 1.0, 0.0);
glTexCoord3f(1.0, 1.0, 0.0); glVertex3f(2.25, 1.0, 0.0);
glTexCoord3f(1.0, 0.0, 0.0); glVertex3f(2.25, -1.0, 0.0);
glEnd();
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 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]);
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
未加上头文件<glext.h>时说版本不对，加上去编译：error C3861: “glTexImage3D”: 找不到标识符
〈不好意思，新人，分数不多，敬请原谅〉
[解决办法]
OpenGL在Windows上从1.2开始，所有扩展函数都需要通过运行时调用wglGetProcAddress获得扩展函数指针之后才能使用。
首先你需要定义一个全局函数指针PFNGLTEXIMAGE3DPROC glTexImage3D;
然后在OpenGL初始化成功后执行glTexImage3D = reinterpret_cast< PFNGLTEXIMAGE3DPROC>( ::wglGetProcAddress( "glTexImage3D") );
如果glTexImage3D不为NULL就可以正常使用了。
glext.h中只有PFNGLTEXIMAGE3DPROC的声明，你需要自己定义glTexImage3D。
