fill element array buffer without modifying VAO (4.1)

Question

I would like to fill a VBO with element indices, and then later bind it to the GL_ELEMENT_ARRAY_BUFFER slot on a VAO.

The obvious (but wrong) code is:

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementArrayBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, ...);

but that changes the current VAO, or could cause an error if there is no VAO bound. I don't want to do that, I just want to fill the buffer, and then use it at some later point

If this would be OpenGL 4.5 (which osx doesn't support), the solution would be to just use glNamedBufferData, and not bind it until later.

Is there a reasonable way around this?

Can i use the GL_ARRAY_BUFFER slot to fill the buffer, and then bind it to GL_ELEMENT_ARRAY_BUFFER later, or would that be against the spec?

Interesting question. Can I ask what you're trying to do?

radical7
– radical7

2017-07-14 01:31:41 +00:00
Commented Jul 14, 2017 at 1:31 — radical7
– radical7, Commented Jul 14, 2017 at 1:31

Nicol Bolas · Accepted Answer · 2017-07-14 01:08:07Z

3

Buffer objects are in no way directly associated with particular targets. When you bind a buffer for the purpose of modifying it, you can bind it to any valid buffer target. You could bind it to GL_COPY_READ_BUFFER just to call glBufferSubData on it. You could also use GL_ARRAY_BUFFER, but for such circumstances, it's best to use an innocuous binding point.

answered Jul 14, 2017 at 1:08

Nicol Bolas

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