In which programming language/s are DirectX & OpenGL written (specially their core part like Kernel)?
DirectX? Mostly a mix of C and C++
OpenGL? English, because OpenGL itself is just a specification document, written in technical prose. Most of the OpenGL implementations out there are also written in a mix of C and C++.
Both OpenGL and DirectX are specifications of an API. They are not limited to one programming language. Different implementations might use different languages.
OpenGL is typically implemented by system libraries or provided by your graphics driver. If you are interested in the programming language you have to check which one is used by your specific implementation.
For DirectX the implementation on Windows might be the most common, but it is not the only one. For example emulators or the WINE runtime environment for windows programs on linux also implement the DirectX API (which in many cases is done by using the OpenGL implementation of the underlying host system).
Related
I'm started looking for docs for OpenGL ES learning, I came across lot of links. one of them has explained like "OpenGL need to be supported by the vendors of Graphics Cards (like NVidia) and be implemented by the OS's vendors (like Apple in his MacOS and iOS) and finally, the OpenGL give to us, developers, a unified API to work with".
what does it mean by?
OpenGL need to be supported by the vendors of Graphics Cards (like NVidia)
Is it something different to normal code libraries execution?
be implemented by the OS's vendors (like Apple in his MacOS and iOS)...
Is this OS's vendor specific?
If all implementation was done by vendors, what does actually OpenGL ES will do?
I was thinking OpenGLES is a library, which needs to install in required OS and using the specific EGL API's, we need to call them? isn't it?
finally the OpenGL give to us, developers, a unified API to work with
If Os itself developing everything, why to go for OpenGL ES?
Please explain, possibly with an example.
Unlike his name suggests, OpenGL is not a library. Or better, it is cause some symbols for the functions you use need to be linked to the executable.
But OpenGL is a standard de facto library, and a great part of the OSes have a good part of the implementation in their kernel. OSX and iOS provide the OpenGL.framework and GLKit.framework to interface with OpenGL
Architecture Review Board ARB just gives specification of OpenGL. This means It tells what should be name of function which parameters it should accept and what is desired behavior. All the Graphics card vendors take this specification and implement this api. Here function interface and high level working is defined by ARB but internal implementation of API is done depending upon the hardware of vendor. Now this OpenGL API goes into driver. Drivers are generally implemented as Operating system interface part and hardware interface part. So Operating system also need some support for this driver.
As I understand GPU vendors defined standard interface to be used by OS Developers to communicate with their specific driver. So DirectX and OpenGL are just wrappers for that interface. When OS developers decide to create new version of Graphic API , GPU vendors expand their interface (new routines are faster and older ones are left for compatibility issues) and OS developers use this new part of interface.
So, when it is said that GPU vendors' support for DirectX is better than for OpenGL, does it simply mean that GPU vendors primarily take into account Microsoft's future plans of developing DirectX API structure and adjust future development of this interface to their needs? Or there is some technical reasons before this?
As I understand GPU vendors defined standard interface to be used by OS Developers to communicate with their specific driver. So DirectX and OpenGL are just wrappers for that interface.
No, not really. DirectX and OpenGL are just specifications that define APIs. But a specification is nothing more than a document, not software. The OpenGL API specification is controlled by Khronos, the DirectX API specification is controlled by Microsoft. Each OS then defines a so called ABI (Application Binary Interface) that specifies which system level APIs are supported by the OS (OpenGL and DirectX are system level APIs) and what rules an actual implementation must adhere to, when being run on the OS in question.
The actual OpenGL or Direct3D implementation happens in the hardware's drivers (and in fact the hardware itself is part of the implementation as well).
When OS developers decide to create new version of Graphic API , GPU vendors expand their interface
In fact it's the other way round: Most of the graphic APIs specifications are laid out by the graphics hardware vendors. After all they are close to where the rubber hits the road. In the case of Khronos the GPU makers are part of the controlling group of Khronos. In the case of DirectX the hardware makers submit drafts to and review the changes and suggestions made by Microsoft. But in the end each new APIs release reflects the common denominator of the capabilities of the next hardware generation in development.
So, when it is said that GPU vendors' support for DirectX is better than for OpenGL, does it simply mean that GPU vendors primarily take into account Microsoft's future plans of developing DirectX API structure and adjust future development of this interface to their needs?
No, it means that each GPU vendor implements his own version of OpenGL and the Direct3D backend, which is where all the magic happens. However OpenGL puts a lot of emphasis on backward compatibility and ease of transition to newer functionality. Direct3D development OTOH is quick in cutting the ties with earlier versions. This also means that full blown compatibility profile OpenGL implementations are quite complex beasts. That's also the reason why recent versions of OpenGL core profiles did (overdue) work in cutting down support for legacy features; this reduction of API complexity is also quite a liberating thing for developers. If you develop purely for a core profile it simplifies a lot of things; for example you no longer have to worry about a plethora of internal state when writing plugin.
Another factor is, that for Direct3D there's exactly one shader compiler, which is not part of the driver infrastructure / implementation itself, but gets run at program build time. OpenGL implementations however must implement their own GLSL shader compiler, which complicates things. IMHO the lack of a unified AST or immediate shader code is one of the major shortcomings of OpenGL.
There is not a 1:1 correspondence between the graphics hardware abstraction and graphics API like OpenGL and Direct3D. WDDM, which is Windows Vista's driver model defines things like common scheduling, memory management, etc. so that DirectX and OpenGL applications work interoperably, but very little of the design of DirectX, OpenGL or GPUs in general has to do with this. Think of it like the kernel, nobody creates a CPU specifically to run it, and you do not have to re-compile the kernel everytime a new iteration of a processor architecture comes out that adds a new subset of instructions.
Application developers and IHVs (GPU vendors, as you call them) are the ones who primarily deal with changes to GPU architecture. It may appear that the operating system has more to do with the equation than it actually does because Microsoft (more so) and Apple--who both maintain their own proprietary operating systems--are influential in the design of DirectX and OpenGL. These days OpenGL closely follows the development of commodity desktop GPU hardware, but this was not always the case - it contains baggage from the days of custom SGI workstations and lots of things in compatibility profiles have not been hardware native on desktop GPUs in decades. DirectX, on the other hand, has always followed desktop hardware. It used to be if you wanted an indication of where desktop GPUs were headed, D3D was a good marker.
OpenGL is arguably more complicated than DirectX because until recently it never let go of anything, whereas DirectX radically redefined the API and stripped legacy support with every iteration. Both APIs have settled down in recent years, but D3D still maintains a bit of an edge considering it only has to be implemented on a single platform and Microsoft writes the one and only shader compiler. If anything, the shader compiler and minimal feature set (void of legacy baggage) in D3D is probably why you get the impression that vendors support it better.
With the emergence of AMD Mantle, the desktop picture might change again (think back to the days of 3Dfx and Glide)... it certainly goes to show that OS developers have very little to do with graphics API design. NV and AMD both have proprietary APIs on the PS3, GameCube/Wii/WiiU, and PS4 that they have to implement in addition to D3D and OpenGL on the desktop, so the overall picture is much broader than you think.
Some virtual machines do not have displayed card at all. I am wondering OpenGL and DirectX can be simulated by software totally or not?
OpenGL and DirectX are just APIs. The actual implementation may be done in hardware or software. The OpenGL interface DLL shipped by Windows contains a OpenGL-1.1 software rasterizer. The OpenGL implementation used on Linux, Mesa3D, also contains a software rasterizer fallback, implementing OpenGL-2.1.
Direct3D can be implemented in software emulated as, but normally isn't.
The simple answer is yes, and companies like Adobe do just that.
Take a look at SwiftShader:: http://transgaming.com/business/swiftshader
I have to used it before and it runs quite well.
When there is a program,which consists of normal c++ code and opengl code.
So,both c++ and opengl are compiled and linked to ELF.
And,seemingly they both run on CPU.
Why opengl code has more power to paint on screen than c++ code ?
Why opengl code has more power to paint on screen than c++ code?
Because OpenGL merely sends drawing commands to the GPU, which is then doing the bulk work. Note that there are also OpenGL implementations that are not GPU accelerated and therefore not faster than other software rasterizers running on the CPU.
Unless you're talking about GLSL, there is no distinction between "C++ code" and "OpenGL code". It's all just C or C++, depending on what you're building. OpenGL is an API, a library that contains functions that do stuff.
Your code calls OpenGL functions, which are functionally no different from any other C++ function you might call. Functions in C++ do something, based on how they're implemented.
OpenGL functions tell the GPU what to do, using GPU-specific constructs. That's what OpenGL is for: to abstract away the specifics of hardware, so that you can write code that is not hardware-dependent. Your code that calls OpenGL functions should work on any OpenGL implementation that supports your minimum GL version (and extensions, if you're using those).
Similarly, std::fstream abstracts away differences between, say, Windows and Linux file access commands. Same API for the user, but it has different implementations on different OS's.
What is the difference between OpenGL and Direct3D? Are they truly different implementations to accomplish the same things (like Java and Mirosoft's CLR [.NET])?
They are very different graphics API's. But it's fair to say they mostly accomplish the same thing. DirectX is probably the API of choice if you are developing a game under windows (or a game for XBOX), and OpenGL is the choice if you want cross-platform support. Mac OS uses GL, as does the iPhone, for example, and many windows games also support OpenGL.
Because OpenGL was developed over a long time and 'by committee', it comes with a lot of baggage - the API has some older options that aren't really relevant today. That's one of the reasons for OpenGL ES; it cuts out all the junk and makes for an easier target platform.
DirectX on the other hand is controlled by Microsoft, and as such it has a more 'modern' feel to it (it's based on COM components, so is highly object oriented). MS often update the API to match new hardware.
Sometimes you don't have the luxury of choice (iphone for example can't run DX). But often it just comes down to personal preference/experience. If your a long-time graphics programmer, you tend to get pretty familiar with both...
Google is your friend in this case...there's a good Wikipedia article contrastring the two libraries:
Comparison of OpenGL and Direct3D
If memory serves, OpenGL was the open implementation before Direct3D came out. Direct3D was then based off of OpenGL...but quickly diverged and became it's own distinct library.
UPDATE
Looks like my memory is shot...
Direct3D was developed independtly of OpenGL.
Direct3D and OpenGL are different API's used to accomplish the same thing.
The major differences between D3D and GL is that D3D is Object Oriented and GL is not.
D3D9 and GLES2 basically have the same features. In fact if you plan on using OpenGL and do not need any GL3 or GL4 features you should base all you code on the GLES2 API(all GLES2 features are in GL2, but not the other way around).
If possible you should always use D3D over GL on windows, as multithreading and driver support is flaky. Take the netbooks for example, they support D3D's HLSL at ShaderModel 2 but don't support the equivalent for GLSL, they only support a fixed pipeline for GL.