CODEWITHSUNDEEP
c++opengl
KTC
KTC

Reputation: 420

glDrawElements crashing

During every call to glDrawElements, my graphics driver crashes/freezes and recovers after a few seconds (Windows 7 Timeout Detection/Recovery). glGetError() always returns GL_NO_ERROR.

Edit: Just to be clear about what exactly happens: the first time glDrawElements is called, my computer freezes for 5-10 seconds, then the screen goes black for a few more seconds, then it recovers and Windows gives me a message: "Display driver stopped responding and has recovered". My program keeps running, but it's stuck in glDrawElements.

Update: Adding a call to glFlush() just before glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) makes it work. I don't understand why.

Here's my code, somewhat simplified and without error checking. Am I doing anything wrong?

struct Vertex
{
    float pos[3];
    float color[3];
};

struct Tri
{
    unsigned int idxs[3];
};

// ...

GLuint m_vbo;
GLuint m_ibo;

std::vector<Vertex> m_verts;
std::vector<Tri> m_faces;

// ...

glGenBuffers(1, &m_vbo);

Vertex* vBuf = &(m_verts[0]);
unsigned int vboSize = sizeof(vBuf[0]) * m_verts.size();

glBindBuffer(GL_ARRAY_BUFFER, m_vbo);
glBufferData(GL_ARRAY_BUFFER, vboSize, vBuf, GL_STATIC_DRAW);

glGenBuffers(1, &m_ibo);

unsigned int* iBuf = (unsigned int*) (&(m_faces[0]));
unsigned int iboSize = sizeof(iBuf[0]) * (m_faces.size() * 3);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_ibo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, iboSize, iBuf, GL_STATIC_DRAW);

// ...

// this line fixes it
// glFlush();

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(someShaderProgram);

// ...

glBindBuffer(GL_ARRAY_BUFFER, m_vbo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_ibo);

// the attribute locations are queried using glGetAttribLocation in the real code
glEnableVertexAttribArray(1);
glVertexAttribPointer
    (1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)(0));

glEnableVertexAttribArray(0);
glVertexAttribPointer
    (0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)(3*sizeof(float)));

// doesn't get past this line
glDrawElements(GL_TRIANGLES, m_faces.size()*3, GL_UNSIGNED_INT, 0);

// ...

glfwSwapBuffers();

Upvotes: 1

Views: 2779

Answers (1)

cooky451
cooky451

Reputation: 3510

The last argument for glVertexAttribPointer is "a offset of the first component" - in byte(!). Are you sure you want the value 3 there?

Upvotes: 1

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