Question

Here is my issue. I have a std::vector<POINTFLOAT> Which stores verticies. The issue is that Vertex buffer objects take in a pointer to an array of float. Therein lies my problem. I cannot give it an array of pointfloat. Is there a way that I could instead push pointers to the individual components of each vertex without pushing in copies?

basically instead of it being:

vec[0].x
vec[0].y
vec[1].x
vec[1].y

It becomes

newvec[0]
newvec[1]
newvec[2]
newvec[3]

I thought of making a std::vector<float*> but I don’t think opengl would like this. Is there a way to do this without copying data?

Thanks

Instead of having to copy data for point.x, point.y, I want OpenGL to get its data from the original vector so basically when openGL would get vec[0] it would actually get pointvec[0].x but it needs to act like when passing by reference, no pointed members

so Opengl cant do *vec[0]

Answer 1

You can write something like this, ie you have a std::vector which you fill with vertices, and then you call a function (eg an openGL function) which takes a float*. Is that what you want?

void some_function(float* data)
{

}

...

std::vector<float> vec;
vec.push_back(1.2); // x1
vec.push_back(3.4); // y1
vec.push_back(5.6); // x2
vec.push_back(7.8); // y2

some_function(&vec[0]);

EDIT: This will also work, because the floats are laid out the same in memory:

struct POINTFLOAT
{
    float x;
    float y;
};

void some_function(float* data)
{

}

...

std::vector<POINTFLOAT> vec;
vec.resize(2);
vec[0].x = 1.2; // x1
vec[0].y = 3.4; // y1
vec[1].x = 5.6; // x2
vec[1].y = 7.8; // y2

some_function((float*)(&vec[0]));