I have missing opengl32 library (more details: mingw32 w64 missing OpenGL32 lib). I have several questions related to this library:
Why I need opengl32 static library ( I have .dll)?
Why video card vendors does not provide this library?
Who should provide it?
Is there a source code of opengl32 library?
Why I need GLEW or other GL library implementations (to use all features of OpenGL) if there is opengl32? Why opengl32 cannot have all required GL implementation?
Why I need opengl32 static library ( I have .dll)?
It provides the symbol table for the linker. The symbol table tells the linker which functions are provided by the library, so that the linker knows how to tie the symbols used in the program, to the libraries linked.
Note that on other OSs than windows, the "DLL" does also provide the symbol tables.
Why video card vendors does not provide this library?
Because the library is part of the OS interfaces to the driver system
Who should provide it?
The DLL: The OS vendor.
The symbol table library: The compiler vendor.
Is there a source code of opengl32 library?
OpenGL itself is just a specification. What you have on your computer is a implementation and a interface. The interface is part of the OS. Hence on closed source OSs there is no source code available, but on open source OSs there is.
Why I need GLEW or other GL library implementations (to use all features of OpenGL) if there is opengl32?
opengl32.dll is just a interface to the driver system. This interface needs to be the smallest common denominator of OpenGL features, so that a wide range of OpenGL versions and capabilities can be offered through a common interface. However you also want to be able to access newer, and bleeding edge features, for which the extension mechanism exists.
Why opengl32 cannot have all required GL implementation?
opengl32.dll is part of the operating system and if it were part of the OS, then every new version of OpenGL would require a OS update. This is, in fact, the situation of MacOS X.
Also the OpenGL implementation is part of the driver, not the DLL.
It's not a static library, it's the library to dynamically link to the DLL.
Because it's a part of the OS, more or less. The symbols exported from OpenGL32.dll tend to be standard (a particular set of gl... functions) and Microsoft-specific (wgl ones at least). The publicly-known ones don't vary between vendors.
Microsoft does provide it, with their compilers. Any other compiler vendor should as well, since libs can be somewhat compiler-specific.
Mesa is an open-source OpenGL implementation, so the closest you'll get.
You don't, you can get the strings and function pointers manually, it's just extremely tedious. GLEW et al do most of the feature-checks and initialization for you. They don't do anything you can do directly with OpenGL32.dll, but they do make life a lot easier.
Related
i am little bit confused how does opengl32.lib library work - without any extensions for opengl version bigger than 1.1.
Does opengl32 lib implement OpenGL 1.1 functions, or just it's retrieving them from graphic driver as new OpenGL functions? If yes, shouldn't GPU vendors implement OpenGL? Does the opengl32 lib work like a part of graphic driver that implements OpenGL? If I won't have graphic driver installed, will opengl32 work(just the base v. 1.1 of course)? Thanks.
Many years ago, those of OpenGL 1.1, opengl32.dll provided all gl-functions needed. When newer versions came in scene it was also the case that vendors implemented "extensions" functions to standard functions. And there was also the case where two different graphics cards may be installed at once. If all of this should be handled by the OS, then man, what a nightmare!
The solution was that each vendor provides his driver, for example Nvidia's nvoglv32.dll. Now opengl32.dll looks in Windows’ system registry and if it finds a vendor driver loads it and let it handles the gl-stuff. If there's not a vendor implementation then opengl32.dll handles gl-stuff, but only for OGL version 1.1.
opengl32.lib (not .dll) is a linker symbol stub. It says that opengl32.dll is needed by the executable.
opengl32.a is the same as opengl32.lib. The .lib is provided by MS VS and the .a is provided by MingGW.
I am writing an OpenGL based game. It includes just these two libraries: glew, glfw3. In order to run it the user must obviously have OpenGL installed, an assumption which I'd like to bypass.
I've gathered all the appropriate binaries inside the game directory and tried linking to these libraries locally but the compiler claims undefined reference to all their functions. Am I doing something wrong or is it just impossible? I'm using Windows but it fails on Linux for the same reason.
OpenGL is not a library you install, it's an API that's implemented as part of the driver. Your compiler complaining about symbols not resolving is completely unrelated to the situation on the end user's computer. And in your case it simply sounds that you did not tell the compiler / linker which libraries and API interfaces to link into your program binary; your compiler is hence complaining, that some of the internal references don't redolve.
So here it goes: OpenGL is not something you ship with your program, it's part of the graphics drivers and your program must use whatever OpenGL version is installed on the user's machine. For this you dynamically link against libGL.so by passing the compiler-linker option -lGL.
GLEW is a helper library that post-loads dynamically all OpenGL functions not found in the system OpenGL ABI, which hence are not exported through the public symbol table of libGL.so. Rather they're to be loaded dynamically using glXGetProcAddress – a rather tedious task. Be advised that GLEW has some serious issues when it comes to OpenGL-3 and later core profiles.
GLFW is a simplistic framework library for setting up a window having an OpenGL context.
GLEW and GLFW are safe to link statically with your program, and I recommend you do that. Instead of using the -l… flag, add libGLEW.a and libGLFW.a to the list of source files / compilation units to be linked.
http://opengl.org/ and http://www.khronos.org/ seems to be currently unavailable. Is there any good alternative mirror sites?
I am looking for OpenGL 4.4 Libraries and Includes download for VC.
OpenGL is not a library, it's an API specification. What you can download at http://opengl.org are just the specification documents and reference C include headers. But there are no library downloads there because, well, OpenGL is not a library.
The actual OpenGL implementation ships as part of your GPU's driver. That's also what ultimately determines which version of OpenGL you can use: The GPU on the system the program is executed on. The major OpenGL version designates the hardware class. A OpenGL-3 class GPU can not do OpenGL-4 (but a OpenGL-4 can do OpenGL-3 of course).
For all practical means there's nothing you need to download or to install to get working with OpenGL. This is different from DirectX where you need a special SDK. OpenGL has been included into the ABI (Application Binary Interface) of the major operating systems, including Windows, and hence the standard headers ship with compilers targeted at this system.
In your case you'll find the OpenGL base headers being preinstalled with the default installation of Visual-C++.
However newer versions of OpenGL require additional tokens and functions to be defined. That's where extension headers come into play. But since there's no change in the ABI, the actual functions do not come as part of a library but must be loaded at runtime using wglGetProcAddress for each function.
Since this is a tedious process there are OpenGL extension loader wrapper libraries, like GLEW (available at http://glew.sf.net) which package up the extension headers and some library code to do the whole loading thing with just a single command. Since there are things to consider like namespace pollution and interoperability with other means of extension loading, GLEW patches into the regular OpenGL headers with preprocessor macro definitions, so that all compilation units that include GLEW just use GLEW. This makes it look like GLEW replaces the regular headers and interface libraries, but in reality it just builds on and defers to them.
Well, usually you want to use glew or a similiar library in order to get the OpenGL functions. You can grab a copy of glew here: http://glew.sourceforge.net/. The libraries should come bundled with VC so you simply add OpenGL32.lib to your linker's additional dependencies.
From OpenGL wiki:
"For most libraries you are familiar with, you simply #include a header file, make sure a library is linked into your project or makefile, and it all works. OpenGL doesn't work that way."
I work on Windows 64 and I need OpenGL to use it in C++ application. What library I should use? Does microsoft provide its implementation ( I use MinGW, I do not have MS Visual C++ )?
The one that comes with your GPU drivers that you have installed on your machine, Microsoft also provides a software layer for OpenGL emulation but it's stuck at the version 1.1 and it's really old and useless.
What library should I use?
I recommend using GLEW for easy access to functions of OpenGL 1.2 and higher, GLM for mathematics, and one of these image loading libraries.
Does microsoft provide its implementation (of OpenGL)?
Microsoft provides you with the necessary header files and library files to access the OpenGL API. However, in order to use OpenGL functions of version 1.2 and higher, you must use extensions. GLEW does this implicitly for you.
Take a look at glew. It loads needed extensions and core functions.
I want to get ( or build from source) OpenGL library that is statically linked to the crt on Windows.
I don't want my executable to require OPENGL32.dll.
My compiler is Visual C++ 9.
Where do I begin? The OpenGL website directs me to this wiki http://www.opengl.org/wiki/Getting_started
But that wiki tells me "In all three major desktop platforms (Linux, MacOS X, and Windows), OpenGL more or less comes with the system".
I am on Windows. Is this statement true. How do I verify this?
Statically linked OpenGL library on Windows
I don't want my executable to require OPENGL32.dll.
Impossible. End of story. opengl32.dll is provided by microsoft and may be changed after each system update. So you can't static-link it - it is a system component.
You can only static link with mesa3d which emulates OpenGL on CPU. However, it is not fully compliant to OpenGL, so you can get unexpected problems, and you'll still require several system dlls. (my bet is gdi32.dll) for your application. Also, performance will be very bad compared to normal OpenGL.
I believe what you are saying is that you don't want to be forced to make your application link with the C Runtime libraries dynamically (i.e. Multithreaded DLL or Multithreaded Debug DLL in the Properties/C++/Code Generation/Runtime Library setting).
Since OpenGL is a system provided .DLL, you are still free to choose Multithreaded or Multithreaded Debug (both choices statically link to the C Runtime) for your Runtime Library when using OpenGL.