共享顶点数组对象的多个绘制调用

这种方法的目的是通过共享Vao并只为每次抽奖重新绑定缓冲区来避免更改Vao格式(参见glVertexAttribPointer and glVertexAttribFormat: What's the difference?或https://www.youtube.com/watch?v=-bCeNzgiJ8I&t=1860)的成本。
下面是一个不使用元素缓冲区数组的明显示例：Render one VAO containing two VBOs
创建共享视频(每个程序只能创建一次)：

GLuint sharedVao = 0;
glCreateVertexArray(1, &sharedVao);
glBindVertexArray(sharedVao);

glEnableVertexAttribArray(0);
glVertexAttribFormat(0, 3, GL_FLOAT, GL_FALSE, 0);
// binding each attribute from its own buffer so attrib_index == buffer_index
glVertexAttribBinding(0, 0);

glEnableVertexAttribArray(1);
glVertexAttribFormat(1, 2, GL_FLOAT, GL_FALSE, 0);
glVertexAttribBinding(1, 1);

创建网格缓冲区(每个网格只有一次)：

struct Mesh
{
    GLuint m_ebo = 0;
    std::array<GLuint, 2> m_vbos = 0;
    GLuint m_triangleCount = 0;
};

// Binding shared VAO here is mandatory as operations accessing or modifying EBO's
// state are not guaranteed to succeed if it wasn't bound to a VAO.
// However, for every new model, binding the EBO will unbind the previous, and we
// will need to rebind EBO to shared VAO for every draw call.
glBindVertexArray(sharedVao);
glCreateBuffer(1, &mesh.m_ebo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mesh.m_ebo);
glBufferData(
    GL_ELEMENT_ARRAY_BUFFER,
    triangles.size() * sizeof(Triangle),
    triangles.data(),
    GL_STATIC_DRAW);
glBindVertexArray(0);
mesh.m_triangleCount  = triangles.size();

glCreateBuffers(2, mesh.m_vbos.data());
glBindBuffer(GL_ARRAY_BUFFER, mesh.m_vbos[0]);
glBufferData(
    GL_ARRAY_BUFFER,
    positions.size() * sizeof(glm::vec3),
    positions.data(),
    GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, mesh.m_vbos[1]);
glBufferData(
    GL_ARRAY_BUFFER,
    textureCoords.size() * sizeof(glm::vec2),
    textureCoords.data(),
    GL_STATIC_DRAW);

渲染循环：

// Bind shared VAO only once
// If drawing with different set of vertex data bound, use glEnableVertexAttribArray
// or glDisableVertexAttribArray before draw calls
glBindVertexArray(sharedVao);

for (auto const& mesh : meshes)
{
    glBindVertexBuffer(0, mesh.m_vbos[0], 0, sizeof(glm::vec3));
    glBindVertexBuffer(1, mesh.m_vbos[1], 0, sizeof(glm::vec2));

    // This is the key difference with existing example on sharing VAO:
    // EBO must be rebound for every draw (unless 2 draws share the same primitive indices)
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mesh.m_ebo);

    glDrawElements(GL_TRIANGLES, mesh.m_triangleCount * 3, GL_UNSIGNED_INT, nullptr);
}