VBOs with std::vector

Question

I\'ve written a model loader in C++ an OpenGL. I\'ve used std::vectors to store my vertex data, but now I want to pass it to glBufferData(), howeve

Answer 1

If you have a std::vector<T> v, you may obtain a T* pointing to the start of the contiguous data (which is what OpenGL is after) with the expression &v[0].

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In your case, this means passing a Vertex* to glBufferData:

glBufferData(
   GL_ARRAY_BUFFER,
   vertices.size() * sizeof(Vertex),
   &vertices[0],
   GL_STATIC_DRAW
);

Or like this, which is the same:

glBufferData(
   GL_ARRAY_BUFFER,
   vertices.size() * sizeof(Vertex),
   &vertices.front(),
   GL_STATIC_DRAW
);

---

You can rely on implicit conversion from Vertex* to void const* here; that should not pose a problem.

Answer 2

This should do the trick:

&vertices[0]

Some prefer &vertices.front(), but that's more typing and I'm bone lazy.

To be even lazier, you could overload glBufferData thus:

template <class T>
inline void glBufferData(GLenum target, const vector<T>& v, GLenum usage) {
    glBufferData(target, v.size() * sizeof(T), &v[0], usage);
}

Then you can write:

glBufferData(GL_ARRAY_BUFFER, vertices, GL_STATIC_DRAW);

and also avoid bugs (your struct is bigger than 3 * sizeof(float)).