Cant draw multiple objects in opengl - c++

Question

I cant work out why the following code doesn't work, I am attempting to draw 2 shapes, a triangle that is coloured red and a cube that is multi coloured, by themselves they draw perfectly but if I try to draw both at once it gives weird bugs, I have tried changing lines around changing variable's modifying my shaders and I cant seem to get anywhere near the result I want, the current code ends up drawing 2 identical triangles that use the cubes colours.
GLuint VertexArrayID;
glGenVertexArrays(1, &VertexArrayID);
glBindVertexArray(VertexArrayID);
GLuint MatrixID = glGetUniformLocation(shader->id(), "MVP");
glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f);
glm::mat4 View = glm::lookAt(
glm::vec3(4,2,2), // Camera location
glm::vec3(0,0,0), // and looks at the origin
glm::vec3(0,1,0) // Head is up (set to 0,-1,0 to look upside-down)
);
glm::mat4 myMatrix = glm::translate(-2.f,0.f,0.f);
glm::mat4 Model = glm::mat4(1.f);
Model= myMatrix * Model;
glm::mat4 MVP = Projection * View * Model;
glm::mat4 myMatrix2 = glm::translate(2.f,0.f,0.f);
glm::mat4 Model2 = glm::mat4(1.f);
Model2= myMatrix2 * Model2;
glm::mat4 MVP2 = Projection * View * Model2;
glViewport(0, 0, windowWidth, windowHeight); // set viewport to the size of the window
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
shader->bind();
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,(void*)0);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, colourBuffer);
glVertexAttribPointer(1,3,GL_FLOAT,GL_FALSE,0,(void*)0);
glDrawArrays(GL_TRIANGLES,0,12*3);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP2[0][0]);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer2);
glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,(void*)0);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, colourBuffer2);
glVertexAttribPointer(1,3,GL_FLOAT,GL_FALSE,0,(void*)0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
SwapBuffers(hdc);
glDeleteBuffers(1, &vertexBuffer);
glDeleteBuffers(1, &vertexBuffer2);
glDeleteBuffers(1, &colourBuffer);
glDeleteBuffers(1, &colourBuffer2);
shader->unbind();
glDeleteVertexArrays(1, &VertexArrayID);
that's the main code. I create all the buffers in a similar way by basically using variations of the following 3 lines to insert the different buffer names and data,
glGenBuffers(1, &vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glBufferData(GL_ARRAY_BUFFER,sizeof(Cube), Cube, GL_STATIC_DRAW);
fragment shader
#version 330 core
in vec3 fragmentColour;
out vec3 colour;
void main(){
colour = fragmentColour;
}
vertex shader
#version 330 core
uniform mat4 MVP;
layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 1) in vec3 vertexColour;
out vec3 fragmentColour;
void main(){
gl_Position = MVP * vec4(vertexPosition_modelspace,1);
fragmentColour = vertexColour;
}

Answer 1

I see you are trying to use VAOs but you create only one.Also why do you prepare:
glEnableVertexAttribArray(0); glBindBuffer(GL_ARRAY_BUFFER,
vertexBuffer);
glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,(void*)0);
glEnableVertexAttribArray(1); glBindBuffer(GL_ARRAY_BUFFER,
colourBuffer);
glVertexAttribPointer(1,3,GL_FLOAT,GL_FALSE,0,(void*)0);
and delete:
glDeleteBuffers(1, &vertexBuffer); glDeleteBuffers(1, &vertexBuffer2);
glDeleteBuffers(1, &colourBuffer); glDeleteBuffers(1, &colourBuffer2);
your VAOs on each render call?The whole purpose of VAOs is to init all the needed buffers and attributes once and then bind only the VAO itself for the actual rendering.Do it on the initialization setup and delete only when you don't need those objects anymore.Here is a good example how it is done properly .
What you should do is this:
Initiate your VAOs in some init method only once.Then in render loop :
glBindVertexArray(m_VAO1);
///draw geometry here
glBindVertexArray(0);
Do this for each geometry you want to render.
After deeper review of your code I see you do this :
GLuint VertexArrayID;
glGenVertexArrays(1, &VertexArrayID);
glBindVertexArray(VertexArrayID);
So you do bind VAO.But you create and bind only one!You need to create one per renderable object,Attach to it all required buffers and then use them in the render loop as I explained above.