Deprecated OpenGL features

Question

I recently read this list and I noticed that almost everything I studied from the OpenGL Red Book is considered deprecated. I\'m talking about pixel transfer operations, pix

Answer 1

Why did they flag these features as deprecated?

First, some terminology: they aren't deprected. In OpenGL 3.0, they are deprecated (meaning "may be removed in later versions"); in 3.1 and above, most of them are removed. The compatibility profile brings the removed features back. And while it is widely implemented on Windows and Linux, Apple's 3.2 implementation only implements the core profile.

As to the reasoning behind the removal, it depends on which feature you're talking about. We can really only speculate as to why the ARB any specific feature:

pixel transfer operations

Pixel transfer operations have not been removed. If you're talking about glDrawPixels, that is a pixel transfer operation, but it is one pixel transfer. Not all of them.

Speaking of which:

pixel drawings

Because it was a horrible idea to begin with. glDrawPixels is a performance trap; it sounds nice and neat, but it performs terribly and because it's simple, people will try to use it.

Having something that is easy to do but terrible in performance encourages people to write terrible OpenGL applications.

accumulation buffer

Shaders can do this just fine. Better in fact; they have a lot more options than accumulation buffers cover.

Begin/End functions (!?),

It's another performance trap. Immediate mode rendering is terribly slow.

automatic mipmap generation

Because it was a terrible idea to begin with. Having OpenGL decide when to do a heavyweight operation like generate mipmaps of a texture is not a good idea. The much better idea the ARB had was to just let you say, "OK, OpenGL, generate some mipmaps for this texture right now."

current raster position.

Another performance trap/bad idea.

Will it be okay to still use them?

That's up to you. NVIDIA has effectively pledged to support the compatibility profile in perpetuity. Which means that AMD and Intel probably will have to as well. So that covers Windows and Linux.

On MacOSX, Apple controls the GL implementations more rigidly, and they seem committed to not supporting the compatibility profile. However, they seem to have little interest in advancing OpenGL, since they stopped with 3.2. Even Mountain Lion didn't update the OpenGL version.

What are the workarounds?

Stop using performance traps. Use buffer objects for your vertex data like everyone else. Use shaders. Use glGenerateMipmap.