opengl 给立方体的6个面贴不同的纹理

要给立方体的6个面贴不同的纹理，可以按照以下步骤进行操作：

1. 定义立方体的顶点坐标和纹理坐标
首先需要定义立方体的顶点坐标和纹理坐标。对于每个面，都需要指定4个顶点和对应的纹理坐标。可以使用以下代码定义立方体的顶点坐标和纹理坐标：

GLfloat vertices[] = {
    // 前面
    -0.5f, -0.5f,  0.5f, 0.0f, 0.0f,
     0.5f, -0.5f,  0.5f, 1.0f, 0.0f,
     0.5f,  0.5f,  0.5f, 1.0f, 1.0f,
    -0.5f,  0.5f,  0.5f, 0.0f, 1.0f,
    // 后面
     0.5f, -0.5f, -0.5f, 0.0f, 0.0f,
    -0.5f, -0.5f, -0.5f, 1.0f, 0.0f,
    -0.5f,  0.5f, -0.5f, 1.0f, 1.0f,
     0.5f,  0.5f, -0.5f, 0.0f, 1.0f,
    // 左面
    -0.5f, -0.5f, -0.5f, 0.0f, 0.0f,
    -0.5f, -0.5f,  0.5f, 1.0f, 0.0f,
    -0.5f,  0.5f,  0.5f, 1.0f, 1.0f,
    -0.5f,  0.5f, -0.5f, 0.0f, 1.0f,
    // 右面
     0.5f, -0.5f,  0.5f, 0.0f, 0.0f,
     0.5f, -0.5f, -0.5f, 1.0f, 0.0f,
     0.5f,  0.5f, -0.5f, 1.0f, 1.0f,
     0.5f,  0.5f,  0.5f, 0.0f, 1.0f,
    // 上面
    -0.5f,  0.5f,  0.5f, 0.0f, 0.0f,
     0.5f,  0.5f,  0.5f, 1.0f, 0.0f,
     0.5f,  0.5f, -0.5f, 1.0f, 1.0f,
    -0.5f,  0.5f, -0.5f, 0.0f, 1.0f,
    // 下面
    -0.5f, -0.5f, -0.5f, 0.0f, 0.0f,
     0.5f, -0.5f, -0.5f, 1.0f, 0.0f,
     0.5f, -0.5f,  0.5f, 1.0f, 1.0f,
    -0.5f, -0.5f,  0.5f, 0.0f, 1.0f,
};

其中，每个顶点的坐标由3个GLfloat类型的数值组成，分别表示x、y、z三个轴的坐标。每个顶点的纹理坐标由2个GLfloat类型的数值组成，分别表示纹理坐标系下的u、v坐标。

2. 加载纹理图片
然后需要加载6张不同的纹理图片。可以使用SOIL库（Simple OpenGL Image Library）来加载图片。使用以下代码加载纹理图片：

GLuint texture[6];

// 加载纹理图片
texture[0] = SOIL_load_OGL_texture("front.jpg", SOIL_LOAD_AUTO, SOIL_CREATE_NEW_ID, SOIL_FLAG_INVERT_Y);
texture[1] = SOIL_load_OGL_texture("back.jpg", SOIL_LOAD_AUTO, SOIL_CREATE_NEW_ID, SOIL_FLAG_INVERT_Y);
texture[2] = SOIL_load_OGL_texture("left.jpg", SOIL_LOAD_AUTO, SOIL_CREATE_NEW_ID, SOIL_FLAG_INVERT_Y);
texture[3] = SOIL_load_OGL_texture("right.jpg", SOIL_LOAD_AUTO, SOIL_CREATE_NEW_ID, SOIL_FLAG_INVERT_Y);
texture[4] = SOIL_load_OGL_texture("up.jpg", SOIL_LOAD_AUTO, SOIL_CREATE_NEW_ID, SOIL_FLAG_INVERT_Y);
texture[5] = SOIL_load_OGL_texture("down.jpg", SOIL_LOAD_AUTO, SOIL_CREATE_NEW_ID, SOIL_FLAG_INVERT_Y);

// 设置纹理参数
for (int i = 0; i < 6; i++) {
    glBindTexture(GL_TEXTURE_2D, texture[i]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
}

其中，SOIL_load_OGL_texture函数用于加载图片，第一个参数是图片的路径，第二个参数指定图片的格式，第三个参数是纹理的ID，第四个参数是加载选项。加载完图片后，需要对纹理进行一些设置，例如指定纹理的过滤方式和纹理坐标的环绕方式。

3. 绘制立方体
最后，绘制立方体时需要将6个面分别绑定不同的纹理。可以使用以下代码绘制立方体：

glEnable(GL_TEXTURE_2D);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);

glBindTexture(GL_TEXTURE_2D, texture[0]);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.5f, -0.5f, 0.5f);
glTexCoord2f(1.0f, 0.0f); glVertex3f(0.5f, -0.5f, 0.5f);
glTexCoord2f(1.0f, 1.0f); glVertex3f(0.5f, 0.5f, 0.5f);
glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.5f, 0.5f, 0.5f);
glEnd();

glBindTexture(GL_TEXTURE_2D, texture[1]);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f); glVertex3f(0.5f, -0.5f, -0.5f);
glTexCoord2f(1.0f, 0.0f); glVertex3f(-0.5f, -0.5f, -0.5f);
glTexCoord2f(1.0f, 1.0f); glVertex3f(-0.5f, 0.5f, -0.5f);
glTexCoord2f(0.0f, 1.0f); glVertex3f(0.5f, 0.5f, -0.5f);
glEnd();

glBindTexture(GL_TEXTURE_2D, texture[2]);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.5f, -0.5f, -0.5f);
glTexCoord2f(1.0f, 0.0f); glVertex3f(-0.5f, -0.5f, 0.5f);
glTexCoord2f(1.0f, 1.0f); glVertex3f(-0.5f, 0.5f, 0.5f);
glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.5f, 0.5f, -0.5f);
glEnd();

glBindTexture(GL_TEXTURE_2D, texture[3]);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f); glVertex3f(0.5f, -0.5f, 0.5f);
glTexCoord2f(1.0f, 0.0f); glVertex3f(0.5f, -0.5f, -0.5f);
glTexCoord2f(1.0f, 1.0f); glVertex3f(0.5f, 0.5f, -0.5f);
glTexCoord2f(0.0f, 1.0f); glVertex3f(0.5f, 0.5f, 0.5f);
glEnd();

glBindTexture(GL_TEXTURE_2D, texture[4]);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.5f, 0.5f, 0.5f);
glTexCoord2f(1.0f, 0.0f); glVertex3f(0.5f, 0.5f, 0.5f);
glTexCoord2f(1.0f, 1.0f); glVertex3f(0.5f, 0.5f, -0.5f);
glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.5f, 0.5f, -0.5f);
glEnd();

glBindTexture(GL_TEXTURE_2D, texture[5]);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.5f, -0.5f, -0.5f);
glTexCoord2f(1.0f, 0.0f); glVertex3f(0.5f, -0.5f, -0.5f);
glTexCoord2f(1.0f, 1.0f); glVertex3f(0.5f, -0.5f, 0.5f);
glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.5f, -0.5f, 0.5f);
glEnd();

glDisable(GL_TEXTURE_2D);

其中，glBindTexture函数用于绑定纹理，glTexCoord2f函数用于指定纹理坐标，glBegin和glEnd函数用于定义绘制的几何图形。注意需要在绘制前启用纹理功能，绘制完后再禁用纹理功能。