Troubles with laying out memory for use by OpenGL (glBufferSubData help needed) - c++

Question

So today I wanted to learn how I can use a Vector2 & Color class to send data to OpenGL with pretty clean looking syntax.
The plan is this.
/*
Vector2 (8 bytes)
Color (16 bytes)
Vector2 + Color = 24 bytes
How can memory be laid out like this?
{Vector2, Color},
{Vector2, Color},
{Vector2, Color}
*/
So I have my two arrays of data.
Vector2 vertices[] = {
Vector2(0.0f, 0.5f),
Vector2(0.5f, -0.5f),
Vector2(-0.5f, -0.5f)
};
// colors would be mapped to there respective indexes in the vertices array (i.e colors[0] is mapped to vertices[0])
Color colors[] = {
Color(1.0f, 0.3f, 0.3f),
Color(0.3f, 1.0f, 0.3f),
Color(0.3f, 0.3f, 1.0f)
};
I was able to get a regular triangle rendering at the correct points,
but sending over the color data has been pretty difficult for me to pull off.
The result I currently get is this.
Here's a snippet of the code.
// positions on screen
Vector2 vertices[] = {
Vector2(0.0f, 0.5f),
Vector2(0.5f, -0.5f),
Vector2(-0.5f, -0.5f)
};
// colors for each position
Color colors[] = {
Color(1.0f, 0.3f, 0.3f),
Color(0.3f, 1.0f, 0.3f),
Color(0.3f, 0.3f, 1.0f)
};
// create vertex and array buffers (each bound automatically)
unsigned int vertexArray = createVertexArray();
unsigned int vertexBuffer = createBuffer(GL_ARRAY_BUFFER);
// allocate the data
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices) + sizeof(colors), nullptr, GL_STATIC_DRAW);
// fill up allocated memory
for (int i = 0; i < 3; ++i) {
glBufferSubData(GL_ARRAY_BUFFER, sizeof(Vector2) * i, sizeof(Vector2), &vertices[i]);
glBufferSubData(GL_ARRAY_BUFFER, (sizeof(Vector2) + sizeof(Color)) * (i + 1), sizeof(Color), &colors[i]);
}
// set up vertex attributes
glVertexAttribPointer(0, 2, GL_FLOAT, false, sizeof(Vector2) + sizeof(Color), nullptr);
glVertexAttribPointer(1, 3, GL_FLOAT, false, sizeof(Vector2) + sizeof(Color), (const void*)( sizeof(Vector2) ));
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);

Answer 1

You need to add 1 vertex and 1 color alternately to the buffer:
for (int i = 0; i < 3; ++i)
{
GLintptr offsetV = i * (sizeof(Vector2) + sizeof(Color));
glBufferSubData(GL_ARRAY_BUFFER, offsetV, sizeof(Vector2), &vertices[i]);
GLintptr offsetC = offsetV + sizeof(Vector2);
glBufferSubData(GL_ARRAY_BUFFER, offsetC, sizeof(Color), &colors[i]);
}