show two objects at once - opengl

Question

Well the origins of this questions lie there
https://stackoverflow.com/questions/20820456/strange-behavior-in-application-using-glfw
But I decided to simplify question with less text data and pictures(Now I use triangles)
I've got two objects - both objects are using vbo. I initalize every object using constructor and method init
Character::Character() {
glm::vec3 vert[] = {
glm::vec3(-.5f, -.5f, 0.0f) ,
glm::vec3(.5f, -.5f, 0.0f) ,
glm::vec3(0.0f, .5f, 0.0f)
};
vertices.insert(vertices.begin(), vert, vert + 3);
}
void Character::init() {
glGenBuffers(1, &vertexbuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(glm::vec3) * vertices.size(), &vertices[0], GL_STATIC_DRAW);
}
void Character::draw() {
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
glDrawArrays(GL_TRIANGLES, 0, vertices.size());
glDisableVertexAttribArray(0);
}
In another class glfwinitializer I keep both objects in std::vector<Character>. So in function main I create two objects and then push_back them into vector.
Draw loop is simple - I iterate through vector and call draw method
while(!glfwWindowShouldClose(window))
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
for(int i = 0; i < scene_items.size(); i++) {
scene_items[i]->draw();
}
this->navigator();
glfwSwapBuffers(window);
glfwPollEvents();
}
Method navigator calculates new position of objects when objects are selected. In every method, where I update data of vector vertices I call method
glBufferData(GL_ARRAY_BUFFER, sizeof(glm::vec3) * vertices.size(), &vertices[0], GL_STATIC_DRAW);
For example(method move_offset is called in navigator)
void Character::move_offset(double x_offset, double y_offset) {
for(int i = 0; i < vertices.size(); i++) {
vertices[i].x += x_offset;
vertices[i].y += y_offset;
}
glBufferData(GL_ARRAY_BUFFER, sizeof(glm::vec3) * vertices.size(), &vertices[0], GL_STATIC_DRAW);
};
But two triangles are not shown on the screen at the same time - when I select one object - another object disappears. When I click on disappeared triangle - it appears and another disappears. (There is also one triangle in the initial location but it cannot be moved)
Why? Is there problem with buffers?
EDIT: PROJECT REPRODUCING PROBLEM WITH ADDITIONAL LIBS
visual studio 2010 project (9 mb)
project with libs

Answer 1

I haven't looked at the full source code in the linked project, but from what you have pasted here, you seem not to call glBindBuffer() in your move_offset() method - thus overwriting the buffer of whatever object was last bound (probably the last one drawn in your loop).