c++ - OpenGL 如何知道它应该根据 GL_ARRAY_BUFFER 将顶点绘制到什么位置？

Question

例如，我有如下一段代码:

//Create a vbo and bind it to the GL_ARRAY_BUFFER
glGenBuffers(1, &positionBufferObject);    
glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);

//vertexPosition is an array of floats that stores the position of 3 vertices (x, y, z, w)
glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions), vertexPositions, GL_STATIC_DRAW);

//Enable the vbo at index 0 of the vao (assuming I have stored it previously at index 0)
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);

//Finally draw the triangle
glDrawArrays(GL_TRIANGLES, 0, 3);

我的问题是，glDrawArrays() 如何知道绑定(bind)到 GL_ARRAY_BUFFER 的任何内容都指的是关于位置的信息，而不是关于颜色的信息？

Answer 1

在 gl_Vertex 可用的地方(即不是核心配置文件)，规范调用该位置和顶点属性 0 别名。

来自gl 4.5 compatibility profile specification (第 401/1005 页):

Setting generic vertex attribute zero specifies a vertex, as described in section 10.7.2. Setting any other generic vertex attribute updates the current values of the attribute. There are no current values for vertex attribute zero