opengl drawing a 3d cube with with EBO - c++

Question

I am trying to draw a cube with OPENGL by using EBO, VAO, and VBO.
the first function init the VAO of the cube
initVAO()
{
GLfloat cube_vertices[] = {
// front
-1.0, -1.0, 1.0,
1.0, -1.0, 1.0,
1.0, 1.0, 1.0,
-1.0, 1.0, 1.0,
// back
-1.0, -1.0, -1.0,
1.0, -1.0, -1.0,
1.0, 1.0, -1.0,
-1.0, 1.0, -1.0
};
GLushort cube_elements[] = {
// front
0, 1, 2,
2, 3, 0,
// right
1, 5, 6,
6, 2, 1,
// back
7, 6, 5,
5, 4, 7,
// left
4, 0, 3,
3, 7, 4,
// bottom
4, 5, 1,
1, 0, 4,
// top
3, 2, 6,
6, 7, 3
};
vertices.insert(vertices.begin(), std::begin(cube_vertices), std::end(cube_vertices));
indices.insert(indices.begin(), std::begin(cube_elements), std::end(cube_elements));
/* create vao */
glGenVertexArrays(1, &VAO);
glBindVertexArray(VAO);
/* create ebo */
glGenBuffers(1, &EBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(cube_elements), cube_elements, GL_STATIC_DRAW);
/* create vbo */
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(cube_vertices), cube_vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(0);
/* unbind buffers */
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glBindVertexArray(0);
}
and the second function use it to draw
draw()
{
shader->activateShader();
/* calculate projection matrix */
//TODO:: find a new place for the projection matrix calculation
int width = (GLfloat)ResourceManager::getInstance()->getWindowSize().x;
int height = (GLfloat)ResourceManager::getInstance()->getWindowSize().y;
glm::mat4 proj = glm::perspective(glm::radians(45.0f), (float)width / height, 0.1f, 100.0f);
/* update shader uniforms*/
glUniformMatrix4fv(shader->projectionUniform, 1, GL_FALSE, glm::value_ptr(proj));
glUniformMatrix4fv(shader->viewUniform, 1, GL_FALSE, glm::value_ptr(Engine::getInstance()->camera->createViewMatrix()));
glUniformMatrix4fv(shader->modelUniform, 1, GL_FALSE, glm::value_ptr(transform->createModleMatrix()));
glUniform4f(shader->colorUniform, color.x, color.y, color.z, 1);
glBindVertexArray(VAO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glBindVertexArray(0);
glUseProgram(0);
}
right now the program is not drawing anything and I cant figure out what is wrong with it
I know that the other parts of the code works because I tested it without a EBO and it worked but I don't know what to do.

Answer 1

See Index buffers. The index buffer binding is stated within the Vertex Array Object. When a buffer is bound to the target ELEMENT_ARRAY_BUFFER, then this buffer is associated to the vertex array object which is currently bound. When calling glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0); the binding of the element buffer to the currently bound VAO is broken. Remove this line of code:
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
The type specification in the glDrawElements must match the type of the indices. Since the type of the indexes is GLushort, the specified type must be GL_UNSIGNED_SHORT:
glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, 0);
glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_SHORT, 0);