问题
I'm trying to write a game that deals with many circles (well, Triangle Fans, but you get the idea). Each circle will have an x position, a y position, and a mass property. Every circle's mass property will be different. Also, I want to color some groups of circles different, while keeping a transparent circle center, and fading to opaque along the perimeter of the circles.
I was told to use VBOs, and have been Googling all day. I would like a full example on how I would draw these circles and an explanation as to how VBOs work, while keeping that explanation simple.
回答1:
I have not implemented VBOs myself yet, but from what I understand, they work similar to texture objects. In fact, when I am reminding myself and explaining to others what VBOs are, I like to incorrectly call texture objects 'texture buffer objects', to reinforce the conceptual similarity.
(Not to be mixed with buffer textures from NVIDIA-specified extension GL_EXT_texture_buffer_object.)
So let's think: what are texture objects? They are objects you generate using glGenTextures(). glGenBuffersARB() does similar thing. An analogy applies with glBindTexture() and glBindBufferARB().
(As of OpenGL 1.5, functions glGenBuffers() and glBindBuffer() have entered core OpenGL, so you can use them in place of the extension equivalents.)
But what exactly are these 'texture objects', and what do they do? Well, consider that you can, actually, use glTexture2D() in each frame to set up a texture. Texture objects only serve to reduce traffic between GPU and main memory; instead of sending entire pixel array, you send just the "OpenGL name" (that is, an integer identifier) of the texture object which you know to be static.
VBOs serve similar purpose. Instead of sending the vertex array over and over, you upload the array once using glBufferData() and then send just the "OpenGL name" of the object. They are great for static objects, and not so great for dynamic objects. In fact, many generic 3D engines such as Ogre3D provide you with a way to specify if a mesh is dynamic or static, quite probably in order to let you decide between VBOs and vertex arrays.
For your purposes, VBOs are not the right answer. You want numerous simple objects that are continuously morphing and changing. By simple, I mean those with less than 200 vertices. Unless you intend to write a very smart and complex vertex shader, VBOs are not for you. You want to use vertex arrays, which you can easily manipulate from main CPU and update them each frame without making special calls to graphics card to reupload the entire VBO onto the graphics card (which may turn out slower than just sending vertex arrays).
Here's a quite good letscallit "man page" from nVidia about VBO API. Read it for further info!
回答2:
good vbo tutorial
What you're doing looks like particles, you might want to google "particle rendering" just in case.
来源：https://stackoverflow.com/questions/1484572/how-do-i-use-vertex-buffer-objects-to-render-many-different-circles