Cannot create more than one VAO

Question

I am attempting to create a simple graphics system using modern (3.3) OpenGL for use in a game. Dynamic objects will have dynamic geometry and VBOs will be updated whenever there is a change. This part was very easy to implement. While everything works well so long as only one VAO is used, further calls to glGenVertexArrays don't create another object (printing the ID for the first and the second both returns 1) and something in the VAO initialization for the new objects renders the first one unable to perform any edits. Every "modern OpenGL" tutorial either only uses one object or has some pretty significant conflicts (most often the use of glVertexAttribPointer). The following code is involved with the graphics system of the objects. (Don't know how important this is, but I am using glfw3 for window and and context creation).

Init Game Object (graphics snippet)

glGenVertexArrays(1, &vertexArrayID);
glBindVertexArray(vertexArrayID);
glGenBuffers(1, &vertexCoordBufferID);
glBindBuffer(GL_ARRAY_BUFFER, vertexCoordBufferID);
glBufferData(GL_ARRAY_BUFFER, 2000 * 3 * sizeof(float), nullptr, GL_DYNAMIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
glEnableVertexAttribArray(0);
allocatedVerticies = 2000;

Update Mesh

    //generate mesh
std::vector<float> vertices;
vertices.reserve(voxels.size() * 3 * 12);

//Vertices are added to the vector. This part works. Removed this code for clarity.


vertexCount = vertices.size() / 3;
glBindVertexArray(vertexArrayID);
glBindBuffer(GL_ARRAY_BUFFER, vertexCoordBufferID);
if (allocatedVerticies < vertexCount)
{
    //reallocate the buffers
    glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(float), vertices.data(), GL_DYNAMIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
    allocatedVerticies = vertexCount;
}
else
{
    /////////////////////////////
    //reallocate the buffers- originally a reallocation was not going to be used, but glBufferSubData does not work
    glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(float), vertices.data(), GL_DYNAMIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
    allocatedVerticies = vertexCount;


    ////////////////////////////////////////this does not work for some reason
    //reset data
    //glBufferSubData(GL_ARRAY_BUFFER, 0, vertices.size() * sizeof(float), vertices.data());
}
edited = false;

Render Object

glBindVertexArray(vertexArrayID);
glDrawArrays(GL_TRIANGLES, 0, vertexCount);

If anyone more experienced with OpenGL could point out my mistake, (or some other problem) that would be fantastic.

This code is inside a C++ class? If yes, are you deleting the OpenGL objects in the destructor? Any chance you're accidentally copying the objects? If that sounds possible, I would define private copy constructors and assignment operators to prevent accidental copying. — Reto Koradi, Nov 20 '14 at 05:35
I have already set up the copy constructor and assignment operators to throw an error If they are called. They never do, so I don't think this is related to the problem. — user3736210, Nov 20 '14 at 18:05

score 0 · Answer 1 · answered Dec 23 '14 at 12:59

In code that you provided I see nothing that can cause such a behaviour. Maby you should provide your entire solution that is connected with your rendering for better understanding what is going on in your program?

By the way: if you already defined glVertexAttribPointer() for your buffor you don't have to do it every time you update the data you stored in your vertexCoordBufferID if of course you don't change the data layout and its type. Instead of:

vertexCount = vertices.size() / 3;
glBindVertexArray(vertexArrayID);
glBindBuffer(GL_ARRAY_BUFFER, vertexCoordBufferID);
if (allocatedVerticies < vertexCount)
{
    //reallocate the buffers
    glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(float), vertices.data(), GL_DYNAMIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
    allocatedVerticies = vertexCount;
}

You can use just:

vertexCount = vertices.size() / 3;
glBindBuffer(GL_ARRAY_BUFFER, vertexCoordBufferID);
if (allocatedVerticies < vertexCount)
{
    //reallocate the buffers
    glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(float), vertices.data(), GL_DYNAMIC_DRAW);
    allocatedVerticies = vertexCount;
}

Cannot create more than one VAO

1 Answers1