How to change buffers for glDrawElements - opengl

Question

I am drawing to rectangle using glDrawElements.
glBindVertexArray(m_VAO);
glDrawElements(GL_TRIANGLES, 6 , GL_UNSIGNED_INT, 0);
glBindVertexArray(0);
I want to draw two different geometry one facing the camera and one on the backside.
This is the data for drawing.
verticesRect = {
// Positions // Normal Coords // Texture Coords
(width / 2.0f) + taper, height / 2.0f, 0.0f, 0.0 , 0.0, 1.0 , 1.0f, 0.0f, // Top Right
width / 2.0f, -height / 2.0f, 0.0f, 0.0 , 0.0, 1.0 , 1.0f, 1.0f, // Bottom Right
-width / 2.0f, -height / 2.0f, 0.0f, 0.0 , 0.0, 1.0 , 0.0f, 1.0f, // Bottom Left
(-width / 2.0f) - taper, height / 2.0f, 0.0f, 0.0 , 0.0, 1.0 , 0.0f, 0.0f // Top Left
};
std::vector<float> verticesRectBack = {
// Positions // Normal Coords // Texture Coords
(width / 2.0f) + taper, height / 2.0f, 0.0f, 0.0 , 0.0, -1.0 , 1.0f, 0.0f, // Top Right
width / 2.0f, -height / 2.0f, 0.0f, 0.0 , 0.0, -1.0 , 1.0f, 1.0f, // Bottom Right
-width / 2.0f, -height / 2.0f, 0.0f, 0.0 , 0.0, -1.0 , 0.0f, 1.0f, // Bottom Left
(-width / 2.0f) - taper, height / 2.0f, 0.0f, 0.0 , 0.0, -1.0 , 0.0f, 0.0f // Top Left
};
verticesRect.insert(verticesRect.end(), verticesRectBack.begin(), verticesRectBack.end()); // Combining both the data sets.
This is the VAO , VBO configuration of data.
glGenVertexArrays(1, &m_VAO);
glGenBuffers(1, &m_VBO);
glGenBuffers(1 , &m_EBO);
glBindVertexArray(m_VAO);
glBindBuffer(GL_ARRAY_BUFFER, m_VBO);
glBufferData(GL_ARRAY_BUFFER,verticesRect.size() * sizeof(float), &verticesRect[0], GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indicesTaperRectangle), indicesTaperRectangle, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(2);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
This is the data for indices.
GLuint indicesTaperRectangle[] = { // Note that we start from 0!
0, 1, 3, // First Triangle
1, 2, 3 // Second Triangle
};
Currently i am only able to draw the first rectangle how can i draw the second rectangle.

Answer 1

This has nothing to do with buffers. What you're experiencing is back face culling and you can go by with just a single draw call if you disable it using glDisable(GL_CULL_FACE).
Another option is to make your geometry two rectangles, and flip its winding. For that you can reuse the vertex positions and just duplicate and flip the indices:
GLuint indicesTaperRectangle_FrontAndBack[] = {
0, 1, 3,
1, 2, 3,
3, 2, 1,
3, 1, 0
};