c – OpenGL Multitexturing – glActiveTexture为NULL

我已经开始了一个新项目,我想在其中使用多重纹理.

我以前做过multixexturing,并且得到了我的OpenGL版本的支持

在标题中我有:

GLuint  m_TerrainTexture[3];//heightmap, texture map and detail map
GLuint  m_SkyboxTexture[5]; //left, front, right, back and top textures

PFNGLMULTITEXCOORD2FARBPROC glMultiTexCoord2fARB;
PFNGLACTIVETEXTUREARBPROC   glActiveTexture;

在构造函数中我有:

glActiveTexture = (PFNGLACTIVETEXTUREARBPROC) wglGetProcAddress((LPCSTR)"glActiveTextureARB");
glMultiTexCoord2fARB = (PFNGLMULTITEXCOORD2FARBPROC) wglGetProcAddress((LPCSTR)"glMultiTexCoord2fARB");

if(!glActiveTexture || !glMultiTexCoord2fARB)
{
    MessageBox(NULL, "multitexturing failed", "OGL_D3D Error", MB_OK);
}

glActiveTexture( GL_TEXTURE0_ARB );
...

这显示消息框“multitexturing failed”,glActiveTexture的内容为0x00000000

当它到达glActiveTexture(GL_TEXTURE0_ARB);我收到访问冲突错误

我正在实现MVC图,所以这都在我的terrain视图类中

最佳答案 您引用了代码来加载扩展,如下所示:

PFNGLMULTITEXCOORD2FARBPROC glMultiTexCoord2fARB;
PFNGLACTIVETEXTUREARBPROC   glActiveTexture;

glActiveTexture = (PFNGLACTIVETEXTUREARBPROC) wglGetProcAddress((LPCSTR)"glActiveTextureARB");
glMultiTexCoord2fARB = (PFNGLMULTITEXCOORD2FARBPROC) wglGetProcAddress((LPCSTR)"glMultiTexCoord2fARB");

这是非常有问题的,因为它可能重新定义已经存在的符号. (动态)链接器最终会跳过这个.例如,可能会发生对指针变量glActiveTexture的赋值进入某个地方,但每当调用同名函数时,它会调用从其他地方链接的内容.

在C中,您通常使用预处理器宏和自定义前缀的组合来避免此问题,而无需调整大部分代码.

PFNGLMULTITEXCOORD2FARBPROC myglMultiTexCoord2fARB;
#define glMultiTexCoord2fARB myglMultiTexCoord2fARB

PFNGLACTIVETEXTUREARBPROC   myglActiveTexture;
#define glActiveTexture myglActiveTexture

glActiveTexture = (PFNGLACTIVETEXTUREARBPROC) wglGetProcAddress((LPCSTR)"glActiveTextureARB");
glMultiTexCoord2fARB = (PFNGLMULTITEXCOORD2FARBPROC) wglGetProcAddress((LPCSTR)"glMultiTexCoord2fARB");

如果你有一个有效的渲染上下文并支持扩展,我真的不知道为什么事情会失败的任何其他原因.

点赞