PDA

View Full Version : Fixed function pipeline



Kopelrativ
08-30-2012, 12:49 AM
It is very common to find people using the immediate mode. They usually don't know better, and there is a high risk that it is what you will start with if you look for tutorials on Internet. Not that it has to be wrong, but they should know the pros and cons. Instead of explaining the difference everytime, I want to use a link to somewhere with a good explanation, but I can't find any good. There are some snippets here and there in the Wiki, but no good overall summary.

Any suggestions?

Maybe the Wiki should be extended with a good summary?

Or maybe I simply didn't find a good summary that already exists.

thokra
08-30-2012, 01:05 AM
Maybe we should simply put a sticky post together, like the forum posting guidelines, explaining why legacy GL is still supported even though we're at 4.3 right now and why it makes sense to not use legacy GL anymore. There's a lot of stuff in the Wiki which is explained well and still many people fail to look there first and still come here asking what has already been answered.

With a sticky post at least people are forced to look at it when they browse the forums from the index.

V-man
08-30-2012, 03:28 AM
I would say that you make a specific page for it on the Wiki and also make a sticky forum post. Include the link to the Wiki in your post.

Kopelrativ
08-30-2012, 06:56 AM
I created http://www.opengl.org/wiki/Legacy_OpenGL, and added what came to my mind for now. The idea is not to create a complete reference, but rather a simple summary.

I am not an expert, and probably forgot some major fact or misunderstood something, so please help reviewing it.

thokra
08-30-2012, 07:05 AM
The idea is not to create a complete reference, but rather a simple summary.

I think the Wiki should represent it the other way around. Otherwise, people are going to come back to the forum and keep asking stuff we should have mentioned. :)

EDIT: Skimming the post, as I can't edit stuff myself at this moment, I think focusing on immediate mode attrib submission, which is only a small part of the fixed-function stuff removed, is not too wise. What about tex env? What about fixed lighting? The post should be as comprehensive as possible.

Section How do I know what is what? should probably mention what's written in the spec on deprecated and removed functions. Also, IMHO the title isn't that good. It should probably be something like What is considered legacy OpenGL? and it should mention GL 2.1 as the last version fully supporting the FFP, GL 3.0 deprecating and GL 3.1 removing deprecated features.

Another section in that direction should be What are profiles? to get to the core (eat that) of the matter. This one should also mentioned the failed attempt to actually cut ties to legacy OpenGL.

Maybe we should also mention the hardware side of all of it, especially the introduction of unified shader architectures in contrast to special hardware stages for vertex processing, fragment processing and so on and the mapping of the new programmability approach to this hardware.

I'll try to think of more stuff.