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c++opengl-4

glBufferSubData causes unhandled exception: 0xC0000005

I am trying to make a mesh class using a vao and a vbo.

First I create vectors to hold the data to be buffered:

std::vector<GLfloat> vertices;
std::vector<GLfloat> normals;
std::vector<GLfloat> texCoords;
std::vector<GLushort> indices;

I store data from a file and then I create the buffers:

// Vertex array
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);

// Vertex buffer
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);

// Index buffer
glGenBuffers(1, &ibo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);

I try to fill the buffers like this:

// Reserve space on the GPU (3 GLfloats per vertex, 3 per normal and 2 per texCoord)
glBufferData(GL_ARRAY_BUFFER, vertices.size() * 8 * sizeof(GLfloat), NULL, GL_STATIC_DRAW);
// Load data to the GPU
// Insert vertices at the beginning of the buffer
glBufferSubData(GL_ARRAY_BUFFER, NULL, vertices.size()*3*sizeof(GLfloat), &vertices);
// Insert normals behind vertices
glBufferSubData(GL_ARRAY_BUFFER, vertices.size()*3*sizeof(GLfloat), normals.size()*3*sizeof(GLfloat), &normals);
// Insert texCoords behind normals
glBufferSubData(GL_ARRAY_BUFFER, (vertices.size() + normals.size())*3*sizeof(GLfloat), texCoords.size()*2*sizeof(GLfloat), &texCoords);

// Load the index buffer
glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size()*3*sizeof(GLushort), &indices, GL_STATIC_DRAW);

It breaks when I try to buffer the normal data:

glBufferSubData(GL_ARRAY_BUFFER, vertices.size()*3*sizeof(GLfloat), normals.size()*3*sizeof(GLfloat), &normals);

I get this error:

Unhandled exception at 0x699CEF38 (nvoglv32.dll) in Engine.exe: 0xC0000005: Access violation reading location 0x05C34000.

I have been searching for a while now but I still haven't found a solution. Any information regarding any mistakes I have made are very welcome.

Thanks in advance, Me

Solution

  • The glaring mistake is this:

    glBufferSubData(GL_ARRAY_BUFFER, NULL, vertices.size()*3*sizeof(GLfloat), &vertices);

    To get the data within the vector, you pass the address of the first element, not a pointer to the vector:

    glBufferSubData(GL_ARRAY_BUFFER, NULL, vertices.size()*3*sizeof(GLfloat), &vertices[0]);

    You make the same error in the other lines that call glBufferSubData, including the line where it finally breaks down where you are using the normals vector.

    Also, the vector has to be non-empty before using &vertices[0], or if using C++11, you can use the vertices.data() function instead of &vertices[0].