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different versions of GL

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I know Open GL 2.0 is the latest and greatest version but will programs written in 1.2 still compile and run even if my driver has been updated to 2.0?

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Well supposedly up until OGL 3.0, then everything breaks [sad]

to OP: yes OGL is backwards compatible. actually you'll be using the base sets of functions from the start and need extensions to access anything made after ver. 1.1 (correct me if i'm wrong).

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Original post by Alpha_ProgDes
Well supposedly up until OGL 3.0, then everything breaks [sad]


Incorrect. There is no plan to break backward compatibility with 3.0.

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Original post by gold
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Original post by Alpha_ProgDes
Well supposedly up until OGL 3.0, then everything breaks [sad]


Incorrect. There is no plan to break backward compatibility with 3.0.

I must have mistakenly misinterpreted this from Mr. Rhino:
Quote:
Mr. Rhino says:
There has been talk for a few years of creating a version of OpenGL that doesn't maintain backward compatability, and it has been suggested that this might happen with OpenGL 3.0. But developers and IHVs have indicated that there is too much out there depending on existing functionality to make a fully clean break.

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Thanks guys but I'm a little confused about the extensions. What would I have to do to access the version 1.2 features?

Quote:
Original post by Alpha_ProgDes

to OP: yes OGL is backwards compatible. actually you'll be using the base sets of functions from the start and need extensions to access anything made after ver. 1.1 (correct me if i'm wrong).


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Well I think some things became confused.

The features of OpenGL 1.2 (resp. 2.0) are of course directly supported by any driver that supports OGL 1.2 (resp. 2.0) or higher. Additionally there are extensions that different companies add to OpenGL like ATI, Nvidia, Sun, etc. and also the "official" ARB extensions. Some of them (mainly ARB ones) become standard in newer Versions of OpenGL (as for example Shader support became from an ARB extension in OGL 1.5 to standard feature in 2.0). All these extension functions begin or end with something like ARB, ATI ... to make clear that this is an extension of a external vendor. And these extensions must not be supportet by graphic card drivers. E.g. Nvidia will probably not support all ATI extensions. So if you want to use extensions you have to check, if your driver supports them or not. But if you have an OpenGL 2.0 featuring driver for you graphic card, all standard OpenGL 2.0 features are for sure availabe.

Though there is one little "but" :-) The thing is, even though the driver for sure supports for example OGL 2.0, you might not be able to acces them. Traditionally the OpenGL headers and LIB that come with Microsoft Visual C++ for example only support the function set of OGL 1.1. What you need is new headers and a LIB to get access to OpenGL 2.0 and extensions functionality. But actually that's easy because there are some nice Librarys in the web for that: I use the following http://glew.sourceforge.net/ but others might be as good.

Ok, hope it helped and I didn't confuse you even more :-)

greetz
rapunzel

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Original post by Alpha_ProgDes
I must have mistakenly misinterpreted this from Mr. Rhino:
Quote:
Mr. Rhino says:
There has been talk for a few years of creating a version of OpenGL that doesn't maintain backward compatability, and it has been suggested that this might happen with OpenGL 3.0. But developers and IHVs have indicated that there is too much out there depending on existing functionality to make a fully clean break.


The last sentence is the key: when developing the current proposal, we considered a clean break. Based on feedback we realize this was not acceptable, and revised the plan to provide backward compatibility while focusing future enhancements on a clean core. Old apps will continue to run, and some functionality may be layered, but this is transparent. Future extensions may not define compatibility with the legacy interfaces.

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Original post by gold
The last sentence is the key: when developing the current proposal, we considered a clean break. Based on feedback we realize this was not acceptable, and revised the plan to provide backward compatibility while focusing future enhancements on a clean core. Old apps will continue to run, and some functionality may be layered, but this is transparent. Future extensions may not define compatibility with the legacy interfaces.

Hasn't this already happened to a certain extend with the programmable pipeline ? For example when fragment shaders broke up the long ingrained one-to-one dependency of texture samplers and texture coordinates ? I think that quite a few extension already break compatibility with the old core, and try to hide the fact through some awkward functional connection mechanisms. Not that this is a bad thing, but we could get rid of all that overhead with a clean cut. I mean, come on, who doesn't hate feedback mode ? And I guess support for display lists will also generate some major headaches for IHVs implementing certain extensions...

Although I still think that backwards compatibility is a great strength of OpenGL (compared to D3D, which breaks with every new release), there are a few things I'd like to see removed from the core: support for indexed colour mode, feedback and picking mode, aux buffers, the entire FFP, etc.

Oh and please keep the IM ! This thing is a blessing for UI drawing.

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Original post by Yann L
Although I still think that backwards compatibility is a great strength of OpenGL (compared to D3D, which breaks with every new release), there are a few things I'd like to see removed from the core: support for indexed colour mode, feedback and picking mode, aux buffers, the entire FFP, etc.

Oh and please keep the IM ! This thing is a blessing for UI drawing.

Do you really mean removed or just "not forced to use"?

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Original post by Alpha_ProgDes
Do you really mean removed or just "not forced to use"?

Not forced to use is the status quo. Unfortunately, that still means that driver implementors have to fully support and maintain them, and that might include a lot of repercussions on newer extensions. So yeah, I mean completely removed. The FFP can be reimplemented as a separate extension (yeah, ironic, I know ;) by layering onto the programmable pipeline. Feedback and indexed modes are obsolete and should go away forever. Framebuffer management should be compeletely abstracted into a generic resource management system, even further than the original superbuffer proposal.

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Original post by Yann L
Quote:
Original post by Alpha_ProgDes
Do you really mean removed or just "not forced to use"?

Feedback and indexed modes are obsolete and should go away forever. Framebuffer management should be compeletely abstracted into a generic resource management system, even further than the original superbuffer proposal.


Ditto, I will second that.

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