GL_INVALID_OPERATION when calling gluLookAt

Question

I've been getting into OpenGL on OS X lately (tl;dr: I'm a OpenGL noob) and got some code working that draws a cube. However, I don't see any of the faces (besides the front) since my view isn't translated. I try to use the gluLookAt function to do this translation, but I get an GL_INVALID_OPERATION error. This is how I do my rendering:

// Activate and lock context
[_glView.openGLContext makeCurrentContext];
CGLLockContext(_glView.openGLContext.CGLContextObj);

// Update camera position
gluLookAt(0, 2.0, 0, 0, 0, 0, 0, 1, 0);
gl_GetError();

// Update viewport and render
glViewport(0, 0, _glView.frame.size.width, _glView.frame.size.height);
[_renderer doRender:time];

// Unlock and flush context
CGLUnlockContext(_glView.openGLContext.CGLContextObj);
[_glView.openGLContext flushBuffer];

This code works when I comment out the gluLookAt call, and from what I can gather from the docs, this error is caused by executing gluLookAt between glBegin and glEnd. I don't know if where these are getting called, as I do not call those myself, and wrapping the call to gluLookAt in glBegin and glEnd does not solve the issue.

If it makes a difference, I'm using OpenGL 3.2 Core Profile.

Answer 1

By the way, gluLookAt (...) (and GLU in general) is not a part of OpenGL. This is why you will not find documentation directly explaining the cause of this error.

The only reason it generates GL_INVALID_OPERATION is because behind the scenes it does this: glMultMatrixf (...) (which was a part of GL once upon a time). That is invalid in a core profile context, because there is no matrix stack anymore; anything that was deprecated in GL 3.0 or 3.1 is removed from GL 3.2 (core profile).

If you need gluLookAt / matrix stack functionality on OS X, GLKit provides a suitable collection of replacement utilities. Alternatively, you can use a much more portable (C++ based) library called GLM if you compile using Objective C++.

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Now, the far simpler solution here is not to use a core profile context. If you are using things like gluLookAt (...) you are likely learning legacy OpenGL. You need a context that supports deprecated parts of OpenGL, and on OS X this means you need a 2.1 context.