How do I change buffer data with std::vector? - c++

Question

So my idea is to add more data to the buffer.
My first idea was to use std::vector so I have a non fixed array, that I can add data to.
In the generation of the data:
void initData()
{
std::vector<float> vertices;
std::array<float, 12> verts = {
0.0f, 0.0f,
1.0f, 0.0f,
0.0f, 1.0f,
0.0f, 1.0f,
1.0f, 1.0f,
1.0f, 0.0f
};
for(int i = 0; i < verts.size(); i++)
vertices.push_back(verts[i]);
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(vertices), &vertices[0], GL_DYBAMIC_DRAW);
glGenVertexArrays(1, &VAO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
}
this works just fine!
but then when I want to add more data:
void render()
{
std::vector<float> newVertices;
// Generates new vertices with more data, like I did in the initData()
// for-loop adding it to the new vector (newVertices)
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferSubData(GL_ARRAY_BUFFER, 0, newVertices.size() * sizeof(newVertices), &newVertices[0]);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLE, 0, 6 * theAmountIveGeneratedBefore);
}
that's the part that I can't seem to get to work...
what am I doing wrong??

Answer 1

EDIT: As pointed out in the comments, you can NOT add more data to a buffer using glBufferSubData(). So this answer only points out the mistake in calculating the size of the passed data.
sizeof(newVertices) doesn't give you what you need. The std::vector is a class and is more complicated than a simple array. Also, you don't need its whole size, actually. What you need is actually just the size of a float, since you are multiplying it by the number of elements. So just:
newVertices.size() * sizeof(float)
or
newVertices.size() * sizeof(newVertices[0])