每次调用glBindBuffer时都需要glVertexAttribPointer吗？

Question

在OpenGL(特别是OpenGL ES 2.0)中,每次绑定一个新的VBO时都需要调用glVertexAttribPointer吗？

例如:

glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer1);

glVertexAttribPointer(ATTRIB_POSITION, 2, GL_FLOAT, GL_FALSE, sizeof(vertexStruct), (void*)offsetof(vertexStruct,position));
glEnableVertexAttribArray(ATTRIB_POSITION);
glVertexAttribPointer(ATTRIB_COLOR, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(vertexStruct), (void*)offsetof(vertexStruct,color);
glEnableVertexAttribArray(ATTRIB_COLOR);

glDrawElements(GL_TRIANGLE_STRIP, sizeof(indices)/sizeof(GLubyte), GL_UNSIGNED_BYTE, (void*)0);

// If vertexBuffer2 has the exact same attributes as vertexBuffer1
// is this legal or do the calls to glVertexAttribPointer (and glEnableVertexAttribArray)
// required again?

glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer2);
glDrawElements(GL_TRIANGLE_STRIP, sizeof(indices)/sizeof(GLubyte), GL_UNSIGNED_BYTE, (void*)0);

我知道有些VAO可以解决不必调用glVertexAttribPointer但我想知道在OpenGL中这样做是否可行？

Answer 1

如果你这样做:

glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer1);

glVertexAttribPointer(ATTRIB_POSITION, 2, GL_FLOAT, GL_FALSE, sizeof(vertexStruct), (void*)offsetof(vertexStruct,position));
glEnableVertexAttribArray(ATTRIB_POSITION);
glVertexAttribPointer(ATTRIB_COLOR, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(vertexStruct), (void*)offsetof(vertexStruct,color);
glEnableVertexAttribArray(ATTRIB_COLOR);

glBindBuffer(GL_ARRAY_BUFFER, 0);

glDrawElements(GL_TRIANGLE_STRIP, sizeof(indices)/sizeof(GLubyte), GL_UNSIGNED_BYTE, (void*)0);

你的代码可以正常工作.所有gl*Pointer调用的作用是查看调用GL_ARRAY_BUFFER 函数时存储的内容,并在该缓冲区和该属性之间创建关联.因此,更改用于属性的缓冲区的唯一方法是调用gl*Pointer.