OpenGL VBO设置

Question

我看到了很多关于减少对openGL的调用的信息，但我对管道的了解还不够深入。你能把VBO完全设置在时间头上吗？特别是使用此example，它设置VBO，然后在绘制调用之前，每个帧调用启用/指针设置。VBO在创建时是否可以使用启用/指针设置进行完整设置？

像这样的东西

 Data_Init_Func(...)
 {
 ....

 glGenBuffers(1, &IndexVBOID);
 glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexVBOID);
 glBufferData(GL_ELEMENT_ARRAY_BUFFER, SizeInBytes, NULL, GL_STATIC_DRAW);
 short pindices[YYY];
 pindices[0]=0;
 pindices[1]=5;
 //etc...
 offsetInByte=0;
 glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, offsetInByte, SizeInBytes, pindices);

 glGenBuffers(1, VertexVBOID);
 glBindBuffer(GL_ARRAY_BUFFER, VertexVBOID);
 glBufferData(GL_ARRAY_BUFFER, SizeInBytes, NULL, GL_STATIC_DRAW);4

 //data creation and binding
 ...

 // Normally it seems like this code is PER FRAME... DOES IT NEED TO BE?
 glEnableClientState(GL_VERTEX_ARRAY);
 glEnableClientState(GL_NORMAL_ARRAY); 
 glVertexPointer(3, GL_FLOAT, 64, BUFFER_OFFSET(0));
 glNormalPointer(GL_FLOAT, 64, BUFFER_OFFSET(12));
 glClientActiveTexture(GL_TEXTURE0);
 glEnableClientState(GL_TEXTURE_COORD_ARRAY);    //Notice that after we call            
 glClientActiveTexture, we enable the array
 glTexCoordPointer(2, GL_FLOAT, 64, BUFFER_OFFSET(24));
 glClientActiveTexture(GL_TEXTURE1);
 glEnableClientState(GL_TEXTURE_COORD_ARRAY);    //Notice that after we call
 glClientActiveTexture, we enable the array
 glTexCoordPointer(2, GL_FLOAT, 64, BUFFER_OFFSET(32));
 glClientActiveTexture(GL_TEXTURE2);
 glEnableClientState(GL_TEXTURE_COORD_ARRAY);    //Notice that after we call
 glClientActiveTexture, we enable the array
 glTexCoordPointer(2, GL_FLOAT, 64, BUFFER_OFFSET(40));
 ...
 }

 Draw(...)
 {
 glBindBuffer(GL_ARRAY_BUFFER_ARB, VertexVBOID);         // for vertex coordinates
 glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexVBOID); // for indices

 // DO I NEED TO CALL THE VERTEX ENABLING/POINTER SETUP HERE?

 // draw 6 quads using offset of index array
 glDrawRangeElements(GL_TRIANGLES, x, y, z, GL_UNSIGNED_SHORT, BUFFER_OFFSET(0));

 ...
 }

Answer 1

// DO I NEED TO CALL THE VERTEX ENABLING/POINTER SETUP HERE?

是。

所有属性都不启用，gl*Pointer调用会修改buffer对象本身。您不会告诉buffer对象它正用于位置和法线。把buffer对象看作是一个哑字节数组。

gl*Pointer调用告诉OpenGL如何解释字节数组。它们没有附加到缓冲区。它们不会修改缓冲区。它们只是告诉OpenGL在特定缓冲区中查找特定数据的位置。

如果要存储这些设置并在以后重置它们，则需要一个vertex array object。