OpenGL (1) vertex buffer

1. Vertex buffer object (Vertex Buffer Objects, VBO)

Will be in GPU Memory （ It is often called video memory ） Store a large number of vertices in . Used to manage this memory , The advantage of using these buffer objects is that we can send a large amount of data to the graphics card at one time , Instead of sending once per vertex .

step1. Use glGenBuffers Function and a buffer ID Generate a VBO object

unsigned int VBO;
glGenBuffers(1, &VBO);

OpenGL There are many buffer object types , The buffer type of vertex buffer object is GL_ARRAY_BUFFER.

step2. Use glBindBuffer Function to bind the newly created buffer to GL_ARRAY_BUFFER On the goal

glBindBuffer(GL_ARRAY_BUFFER, VBO);  

From this moment on , Any... We use （ stay GL_ARRAY_BUFFER On the target ） Buffer calls are used to configure the buffer of the current binding (VBO).

step3. You can call glBufferData Function copies the previously defined vertex data into the buffered memory ：

glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

glBufferData Is a function specially used to copy user-defined data to the current binding buffer .
Parameter one ： Type of target buffer , The vertex buffer object is currently bound to GL_ARRAY_BUFFER On the goal .
Parameter two ： Specifies the size of the transferred data ( In bytes ); With a simple sizeof Calculate the vertex data size .
Parameter 3 ： The actual data sent .
Parameter 4 ： Specifies how we want the graphics card to manage the given data . It comes in three forms ：

GL_STATIC_DRAW ： The data will not or will hardly change .
GL_DYNAMIC_DRAW： The data will be changed a lot .
GL_STREAM_DRAW ： Data changes every time it's plotted .
The position data of the triangle will not change , Keep as is every render call , So its best use type is GL_STATIC_DRAW.eg. Say that the data in a buffer will be changed frequently , Then the type used is GL_DYNAMIC_DRAW or GL_STREAM_DRAW, This ensures that the graphics card places the data in the memory part that can be written at high speed .

Now we have stored the vertex data in the memory of the graphics card , use VBO This vertex buffer object is managed .