I'm having trouble rendering some of my meshes; some display just fine, some are drawn wrong or not at all.

While troubleshooting I was looking at the openGL docs (http://www.opengl.org/sdk/docs/man3/) and on the topic of glBufferSubData the following line caught my eye:

Clients must align data elements consistent with the requirements of the client platform, with an additional base-level requirement that an offset within a buffer to a datum comprising N bytes be a multiple of N.

I am buffering vertex + normal and index data like this:

    glGenBuffers(1, &mVBO);
    glGenBuffers(1, &mIndexBuffer);
    glGenVertexArrays(1, &mVAO);
 
    // buffer vertex, normals and index data
    glBindVertexArray(mVAO);
    glBindBuffer(GL_ARRAY_BUFFER, mVBO);
    glBufferData(GL_ARRAY_BUFFER, (vertexData.size() + normalData.size()) * sizeof(float), NULL, GL_STATIC_DRAW);
    glBufferSubData(GL_ARRAY_BUFFER, NULL, vertexData.size() * sizeof(float), &vertexData[0]);
    glBufferSubData(GL_ARRAY_BUFFER, vertexData.size() * sizeof(float), normalData.size() * sizeof(float), &normalData[0]);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mIndexBuffer);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, indexData.size() * sizeof(uint32_t), &indexData[0], GL_STATIC_DRAW);

    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)(vertexData.size() * sizeof(float)));

   // unbind array buffer and VAO
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);

So for the vertex and normals I first allocate the complete buffer using glBufferData and then fill it in using glBufferSubData. My question then is, according to the docs, do I need to align the offset my normal data, and if so with what? Is this what couldve caused some meshes to draw incorrectly?

I'm having trouble rendering some of my meshes; some display just fine, some are drawn wrong or not at all.

While troubleshooting I was looking at the openGL docs (http://www.opengl.org/sdk/docs/man3/) and on the topic of glBufferSubData the following line caught my eye:

Clients must align data elements consistent with the requirements of 
the client platform, with an additional base-level requirement that an offset 
within a buffer to a datum comprising N bytes be a multiple of N.

I am buffering vertex + normal and index data like this:

glGenBuffers(1, &mVBO);
glGenBuffers(1, &mIndexBuffer);
glGenVertexArrays(1, &mVAO);
 
// buffer vertex, normals and index data
glBindVertexArray(mVAO);
glBindBuffer(GL_ARRAY_BUFFER, mVBO);
glBufferData(GL_ARRAY_BUFFER, (vertexData.size() + normalData.size()) * sizeof(float), NULL, GL_STATIC_DRAW);
glBufferSubData(GL_ARRAY_BUFFER, NULL, vertexData.size() * sizeof(float), &vertexData[0]);
glBufferSubData(GL_ARRAY_BUFFER, vertexData.size() * sizeof(float), normalData.size() * sizeof(float), &normalData[0]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mIndexBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, indexData.size() * sizeof(uint32_t), &indexData[0], GL_STATIC_DRAW);

glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)(vertexData.size() * sizeof(float)));

// unbind array buffer and VAO
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);

So for the vertex and normals I first allocate the complete buffer using glBufferData and then fill it in using glBufferSubData. My question then is, according to the docs, do I need to align the offset my normal data, and if so with what? Is this what couldve caused some meshes to draw incorrectly?