OpenGL Problems with Rendering Multiple Objects - c++

Question

I'm brand new to OpenGL and am having some difficulty rendering multiple objects.
I have a vector each of which has its own VertexBuffer. Then, in the while loop I draw each shape on its own.
It's all well and good when I have many of the same objects (multiple cubes etc.) however, when I add a triangle mesh everything gets all out of whack.
I can have many cubes
I can have a single triangle mesh:
But, when I try to have a cube and then a triangle mesh I get:
I'm totally at a loss for what's going on. The code for my loop is provided below.
while (!glfwWindowShouldClose(window))
{
// Get the size of the window
int width, height;
glfwGetWindowSize(window, &width, &height);
float aspect_ratio = 1 * float(height)/float(width); // corresponds to the necessary width scaling
double xpos, ypos;
glfwGetCursorPos(window, &xpos, &ypos);
// Clear the framebuffer
glClearColor(0.5f, 0.5f, 0.5f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Enable depth test
glEnable(GL_DEPTH_TEST);
glUniform3f(program.uniform("triangleColor"), 1.0f, 1.0f, 1.0f);
glUniformMatrix4fv(program.uniform("proj"), 1, GL_FALSE, projection.data());
glUniformMatrix4fv(program.uniform("view"), 1, GL_FALSE, view.data());
int tally = 0;
for (int i = 0; i < surfaces.size(); i++) {
Surface *s = surfaces[i];
Vector3f color = s->getColor();
int tempIndex = triangleIndex;
Matrix4f model = s->getModel();
// Convert screen position to world coordinates
double xworld = ((xpos/double(width))*2)-1;
double yworld = (((height-1-ypos)/double(height))*2)-1; // NOTE: y axis is flipped in glfw
if (isPressed && mode == "translate") {
if(tempIndex == i) {
Vector4f center = s->getCenter() + model.col(3);
Vector4f displacement = Vector4f(xworld, yworld, 0, 1) - center;
Matrix4f translation = translateMatrix(displacement(0), displacement(1), displacement(2));
model = translation * s->getModel();
s->setModel(model);
}
}
glUniform3f(program.uniform("triangleColor"), color(0), color(1), color(2));
glUniformMatrix4fv(program.uniform("model"), 1, GL_FALSE, model.data());
glDrawArrays(GL_TRIANGLES, 0, s->getVertices().size());
}
And I initialize each VBO when making the object as
VertexBufferObject VBO;
VBO.init();
VBO.update(Vertices);
program.bindVertexAttribArray("position", VBO);
Surface* s = new Surface(VBO, Vertices, percentScale, 0, transformedCenter, SmoothNormals, FlatNormals, color);
s->setModel(model);
surfaces.push_back(s);
And where Program::bindVertexAttribArray is defined as
GLint Program::bindVertexAttribArray(
const std::string &name, VertexBufferObject& VBO) const
{
GLint id = attrib(name);
if (id < 0)
return id;
if (VBO.id == 0)
{
glDisableVertexAttribArray(id);
return id;
}
VBO.bind();
glEnableVertexAttribArray(id);
glVertexAttribPointer(id, VBO.rows, GL_FLOAT, GL_FALSE, 0, 0);
check_gl_error();
return id;
}

Answer 1

You're not binding any buffers before the draw call. You're probably simply drawing whatever buffer you last bound when you initialised them. You'll need something like this at the end of your loop before glDrawArrays:
...
program.bindVertexAttribArray("position", VBO); // where VBO is the buffer of surface s
glUniform3f(program.uniform("triangleColor"), color(0), color(1), color(2));
glUniformMatrix4fv(program.uniform("model"), 1, GL_FALSE, model.data());
glDrawArrays(GL_TRIANGLES, 0, s->getVertices().size());