多网格、多VBO、多VAO、OpenGL 4.1

我正在尝试使用OpenGL4.1绘制两个不同的网格。在任何给定的时间，只会绘制一个网格，我的目标是在它们之间切换。我将网格的顶点和索引数据存储在一个对象中，下面称为g_obj。因此，第一个网格的数据通过g_obj->顶点和g_obj->索引获得，第二个网格的数据通过g_obj->顶点和g_obj->索引获得

我可怕的想法是对每个网格使用不同的VBO和VAO。然后在draw调用中，我只需绑定适当的VAO，然后执行glDraw*。但是，我的代码在第一次draw调用时出错，请参见下文

enum VAO_ID 
{
    VAO,
    VAO_LINEAR,
    NUM_VAOS
};

enum BUFFER_ID 
{
    VERTEX_BUFFER,
    VERTEX_BUFFER_LINEAR,
    INDEX_BUFFER,
    INDEX_BUFFER_LINEAR,
    NUM_BUFFERS
};

enum ATTRIBUTE_ID 
{
    VERTEX_POSITION,
    VERTEX_COLOR
};

GLuint g_vaos[NUM_VAOS];
GLuint g_buffers[NUM_BUFFERS];

接下来，我创建顶点/索引缓冲区和顶点数组对象：

void bufferGeometry()
{

   // create vertex buffers and vertex array object 
    glGenVertexArrays(NUM_VAOS, g_vaos);
    glGenBuffers(NUM_BUFFERS, g_buffers);

    // rotational grating
    glBindBuffer(GL_ARRAY_BUFFER, g_buffers[VERTEX_BUFFER]);
    glBufferData(GL_ARRAY_BUFFER,
                 g_obj->num_vertices_ * sizeof(vertex2D),
                 g_obj->vertices_,
                 GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_buffers[INDEX_BUFFER]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER,
                 g_obj->num_indices_ * sizeof(GLushort),
                 g_obj->indices_,
                 GL_STATIC_DRAW);
    glBindVertexArray(g_vaos[VAO]);
    glEnableVertexAttribArray(VERTEX_POSITION);
    glVertexAttribPointer(VERTEX_POSITION, 2, GL_FLOAT, GL_FALSE, 
                          sizeof(vertex2D),
                          (const GLvoid *)offsetof(vertex2D, position));
    glEnableVertexAttribArray(VERTEX_COLOR);
    glVertexAttribPointer(VERTEX_COLOR, 4, GL_UNSIGNED_BYTE, GL_FALSE, 
                          sizeof(vertex2D),
                          (const GLvoid *)offsetof(vertex2D, color));
    glBindVertexArray(0);

    // linear grating
    glBindBuffer(GL_ARRAY_BUFFER, g_buffers[VERTEX_BUFFER_LINEAR]);
    glBufferData(GL_ARRAY_BUFFER,
                 g_obj->num_vertices_linear_ * sizeof(vertex2D),
                 g_obj->vertices_linear_,
                 GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_buffers[INDEX_BUFFER_LINEAR]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER,
                 g_obj->num_indices_linear_ * sizeof(GLushort),
                 g_obj->indices_linear_,
                 GL_STATIC_DRAW);

    glBindVertexArray(g_vaos[VAO_LINEAR]);
    glEnableVertexAttribArray(VERTEX_POSITION);
    glVertexAttribPointer(VERTEX_POSITION, 2, GL_FLOAT, GL_FALSE, 
                          sizeof(vertex2D),
                          (const GLvoid *)offsetof(vertex2D, position));

    glEnableVertexAttribArray(VERTEX_COLOR);
    glVertexAttribPointer(VERTEX_COLOR, 4, GL_UNSIGNED_BYTE, GL_FALSE, 
                          sizeof(vertex2D),
                          (const GLvoid *)offsetof(vertex2D, color));

    glBindVertexArray(0);

}

然后，这里是抽签通知：

glBindVertexArray(g_vaos[VAO]);
g_obj = &g_grating_uno;
glUseProgram(g_program);
glUniform3fv(g_trans_scale_location, 1, g_obj->trans_scale_);
glDrawElements(GL_TRIANGLES, g_obj->num_indices_,
               GL_UNSIGNED_SHORT, (const GLvoid *)0);

在GLD元件线路上出现故障

---

我知道一般的性能策略是将来自两个网格的数据打包到单个VBO中，由于两个网格之间的数据格式相同，因此我只需要一个VAO。但是，由于我懒惰，我想知道是否有人能理解为什么我现有的策略不起作用或不起作用，或者你是否认为问题出在别处。我猜这和我的几何函数有关。我对VAO与特定VBO（如果有的话）之间的联系的理解有点薄弱。谢谢，很抱歉我这么笨

啊，我想通过在绑定VBO之前绑定VAO来修复它：

void bufferGeometry()
{

   // create vertex buffers and vertex array object 
    glGenVertexArrays(NUM_VAOS, g_vaos);
    glGenBuffers(NUM_BUFFERS, g_buffers);

    // rotational grating
    glBindVertexArray(g_vaos[VAO]);
    glBindBuffer(GL_ARRAY_BUFFER, g_buffers[VERTEX_BUFFER]);
    glBufferData(GL_ARRAY_BUFFER,
                 g_obj->num_vertices_ * sizeof(vertex2D),
                 g_obj->vertices_,
                 GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_buffers[INDEX_BUFFER]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER,
                 g_obj->num_indices_ * sizeof(GLushort),
                 g_obj->indices_,
                 GL_STATIC_DRAW);
    glEnableVertexAttribArray(VERTEX_POSITION);
    glVertexAttribPointer(VERTEX_POSITION, 2, GL_FLOAT, GL_FALSE, 
                          sizeof(vertex2D),
                          (const GLvoid *)offsetof(vertex2D, position));
    glEnableVertexAttribArray(VERTEX_COLOR);
    glVertexAttribPointer(VERTEX_COLOR, 4, GL_UNSIGNED_BYTE, GL_FALSE, 
                          sizeof(vertex2D),
                          (const GLvoid *)offsetof(vertex2D, color));
    glBindVertexArray(0);

    // linear grating
    glBindVertexArray(g_vaos[VAO_LINEAR]);
    glBindBuffer(GL_ARRAY_BUFFER, g_buffers[VERTEX_BUFFER_LINEAR]);
    glBufferData(GL_ARRAY_BUFFER,
                 g_obj->num_vertices_linear_ * sizeof(vertex2D),
                 g_obj->vertices_linear_,
                 GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_buffers[INDEX_BUFFER_LINEAR]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER,
                 g_obj->num_indices_linear_ * sizeof(GLushort),
                 g_obj->indices_linear_,
                 GL_STATIC_DRAW);

    glEnableVertexAttribArray(VERTEX_POSITION);
    glVertexAttribPointer(VERTEX_POSITION, 2, GL_FLOAT, GL_FALSE, 
                          sizeof(vertex2D),
                          (const GLvoid *)offsetof(vertex2D, position));

    glEnableVertexAttribArray(VERTEX_COLOR);
    glVertexAttribPointer(VERTEX_COLOR, 4, GL_UNSIGNED_BYTE, GL_FALSE, 
                          sizeof(vertex2D),
                         (const GLvoid *)offsetof(vertex2D, color));

    glBindVertexArray(0);

}

---

您应该重复调用以在glBindVertexArray之间绑定元素缓冲区：

glBindVertexArray(g_vaos[VAO]);
glEnableVertexAttribArray(VERTEX_POSITION);
glVertexAttribPointer(VERTEX_POSITION, 2, GL_FLOAT, GL_FALSE, 
                      sizeof(vertex2D),
                      (const GLvoid *)offsetof(vertex2D, position));
glEnableVertexAttribArray(VERTEX_COLOR);
glVertexAttribPointer(VERTEX_COLOR, 4, GL_UNSIGNED_BYTE, GL_FALSE, 
                      sizeof(vertex2D),
                      (const GLvoid *)offsetof(vertex2D, color));
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_buffers[INDEX_BUFFER]);
glBindVertexArray(0);

---

元素缓冲区绑定是VAO状态的一部分，在绑定新VAO时会重置。

Ah，好的，我也会尝试。谢谢