C++ 带有 std::vector 的 VBO
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VBOs with std::vector
提问by Bojangles
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(), however the data types are wildly different. I want to know if there's a way to convert between std::vectorto the documented const GLvoid *for glBufferData().
我用 C++ 和 OpenGL 编写了一个模型加载器。我已经使用std::vectors 来存储我的顶点数据，但现在我想将它传递给glBufferData()，但是数据类型却大不相同。我想知道如果有之间进行转换的方式std::vector所记录const GLvoid *的glBufferData()。
Vertex type
顶点类型
typedef struct
{
float x, y, z;
float nx, ny, nz;
float u, v;
}
Vertex;
vector<Vertex> vertices;
glBufferData() call
glBufferData() 调用
glBufferData(GL_ARRAY_BUFFER, vertices.size() * 3 * sizeof(float), vertices, GL_STATIC_DRAW);
I get the following (expected) error:
我收到以下（预期的）错误：
error: cannot convert ‘std::vector<Vertex>' to ‘const GLvoid*' in argument passing
How can I convert the vector to a type compatible with glBufferData()?
如何将向量转换为与 兼容的类型glBufferData()？
NB. I don't care about correct memory allocation at the moment; vertices.size() * 3 * sizeof(float)will most likely segfault, but I want to solve the type error first.
注意。我现在不在乎正确的内存分配；vertices.size() * 3 * sizeof(float)很可能会出现段错误，但我想先解决类型错误。
回答by Lightness Races in Orbit
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].
如果您有std::vector<T> v，则可以通过T*表达式获得指向连续数据（这是 OpenGL 所追求的）开头的&v[0]。
In your case, this means passing a Vertex*to glBufferData:
在您的情况下，这意味着将 a 传递Vertex*给glBufferData：
glBufferData(
GL_ARRAY_BUFFER,
vertices.size() * sizeof(Vertex),
&vertices[0],
GL_STATIC_DRAW
);
Or like this, which is the same:
或者像这样，这是一样的：
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.
您可以依赖从这里Vertex*到void const*这里的隐式转换；这应该不会造成问题。
回答by Marcelo Cantos
This should do the trick:
这应该可以解决问题：
&vertices[0]
Some prefer &vertices.front(), but that's more typing and I'm bone lazy.
有些人更喜欢&vertices.front()，但打字更多，而且我很懒惰。
To be even lazier, you could overload glBufferDatathus:
为了更懒惰，您可以glBufferData因此重载：
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:
然后你可以写：
glBufferData(GL_ARRAY_BUFFER, vertices, GL_STATIC_DRAW);
and also avoid bugs (your struct is bigger than 3 * sizeof(float)).
并避免错误（您的结构大于3 * sizeof(float)）。
