Why don't I need to bind my vertex buffer object before calling glDrawArrays?

Posted by valmo on Stack Overflow See other posts from Stack Overflow or by valmo
Published on 2013-11-08T11:52:10Z Indexed on 2013/11/08 15:54 UTC
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I'm a bit confused why this still renders. I thought you need to bind a vertex buffer object so that glDrawArrays knows which vertex buffer to use.

Here is my initialisation code..

// Create and bind vertex array to store vertex attribute states.

glGenVertexArraysOES(NUM_VERTEX_ARRAYS, &m_vertexArray);
glBindVertexArrayOES(m_vertexArray);

// Create and bind vertex buffer to store vertex data.

glGenBuffers(NUM_VERTEX_BUFFERS, &m_vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, m_vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * 36, &m_vertices[0], GL_STATIC_DRAW);

glEnableVertexAttribArray(VertexAttribPosition);
glVertexAttribPointer(VertexAttribPosition, 3, GL_FLOAT, GL_FALSE, 24, BUFFER_OFFSET(0));
glEnableVertexAttribArray(VertexAttribNormal);
glVertexAttribPointer(VertexAttribNormal, 3, GL_FLOAT, GL_FALSE, 24, BUFFER_OFFSET(12));

glBindBuffer(GL_ARRAY_BUFFER, 0);

glBindVertexArrayOES(0);

Here is my render code. I'm confused why glDrawArrays still works when I bind 0 to GL_ARRAY_BUFFER.

glBindVertexArrayOES(m_vertexArray);
glBindBuffer(GL_ARRAY_BUFFER, 0);

glDrawArrays(GL_TRIANGLES, 0, 36);

glBindVertexArrayOES(0);

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