Sign in to follow this  
Vincent_M

OpenGL OpenGL vs DirectX

Recommended Posts

I have been writing a lot of code in OpenGL in the past few years, and I've made sure that the code builds with no errors on Windows as well (coming mainly from Linux and Mac). I want this code to run efficiently on Windows machines, and get re-aquainted with DirectX again though.

 

Would it be more efficient for the Windows build of my code to use DirectX and Windows API over OpenGL/OpenAL/BSD Sockets/pthreads, etc for graphics, sounds, networking, multithreading etc?

Edited by Vincent_M

Share this post


Link to post
Share on other sites

I suggest changing the topic name because current one looks like asking for a meaningless war biggrin.png

 

Rewriting your whole code from openGL to DirectX would be time consuming, I would advise you to only change the strictly operating system bound functions (i think it's obvious one, and I  can see you already achieved that). But if your aim is to learn (or revise) directx, it might be a good idea to do it ;)

Edited by Tasaq

Share this post


Link to post
Share on other sites

Would it be more efficient for the Windows build of my code to use DirectX and Windows API over OpenGL/OpenAL/BSD Sockets/pthreads, etc for graphics, sounds, networking, multithreading etc?

Nope. Why? Because the only part of DirectX that's really meaningful these days is D3D. There's no reason to change your OpenAL/socket/pthread, etc. code to use the old and (hopefully) dying parts of DirectX. Unless you need some kind of platform specific functionality, there's nothing to be gained here.

Now, as for whether you should use OpenGL or D3D... It's up to you. D3D won't be magically more efficient if you just do a straight port.

 

I suggest changing the topic name because current one looks like asking for a meaningless war biggrin.png

100% agree with this!

Edited by Cornstalks

Share this post


Link to post
Share on other sites

I suggest changing the topic name because current one looks like asking for a meaningless war.

 

I second this suggestion - I was seriously considering reporting this thread for mod action before I opened it.

 

Regarding your question, if you really want to learn DirectX, then porting it may be a good way of doing so, but be aware that - with the exception of D3D - almost all of DirectX is gone nowadays.  You could port just the renderer, but if you've got it set up to work nicely with some of GL's quirks (bind-to-modify, I'm looking at you, and don't feel safe shader-management because you're next) you may have a fairly torrid time.  Maybe working through some tutorial material might be a better idea, until you establish a better level of comfort with the API differences.

Share this post


Link to post
Share on other sites

I echo the responses that have been provided so far.  The only real difference between OpenGL and Direct3D would be related to the driver support.  Check your expected GPU vendor support, and make sure they have well supported drivers for the API of your choosing.  If they do, then don't switch.  If they don't, then do switch.

 

If you want to learn D3D, there is no reason to re-implement your previous projects - just do your next one in D3D to freshen up your knowledge.

Share this post


Link to post
Share on other sites

I was concerned with whether this title would cause some sort of flame war lol. I was actually starting to learn programming and DirectX when that was dying down (I think). Can anyone explain on how to change the title?

 

I'm aware of what they both do, and I've got experience with both, I'm just wondering if there's performance issues when using OpenGL in a Windows environment. I've read in different things online regarding API performance since 2010 concerning DirectX and OpenAL/GL/CL libraries. For example, I've heard that Windows drivers for graphics cards seem to support D3D's max capabilities much better than OpenGL in terms of things like shader processing performance, max texture units/texture size/lights/stacks/etc. There was an article mentioning OpenGL dying because of lack of support, which I don't believe is true, however, it's not the first I've heard of it.

Share this post


Link to post
Share on other sites

To generalize... on Windows D3D is more stable/reliable because it's largely implemented by one entity (Microsoft) with the rest implemented by the driver (nVidia/AMD/Intel/etc) according to a strict D3D driver specification from Microsoft.

On the other hand, GL is almost entierly implemented by the driver, and Khronos do not test implementations for compliance with the specification.

 

To be fair, you do find driver bugs occasionally in both D3D and GL, but in my experience GL has the worse reputation in this regard.

 

With features/extensions, sometimes one API provides more capabilities than the other, and it goes both ways. Intel in particular have often lagged behind with their GL driver support, with their D3D driver providing more capabilities than their GL driver... but there are also cases of the opposite.

 

In the D3D9 vs GL days, GL's CPU-side overheads tended to be slightly smaller... however, D3D10/11 are much more efficient than 9 in this regard, so I'd guess that they've closed this gap with GL, and probably even beaten it now, seeing as GL is much more complex due to backwards compatibility  whereas D3D makes a clean break with each version, discarding old cruft. In any case, these performance differences should be very small (e.g. a millisecond per frame...).

 

There is one annoying case with GL that can cause poor performance -- many drivers when asked to perform a function that is not supported in hardware, will resort to CPU-emulation of that feature. For example, I added array indexing to a pixel shader once, but my GPU only supported this feature in vertex shaders, so my driver decided that instead of failing to draw anything, it would instead run my pixel shader in software emulation on the CPU, at 1 frame per second... GL has a lot more of these kinds of fast-path/slow-path pitfalls compared to D3D.

Share this post


Link to post
Share on other sites

Well written GL is probably slower than well written D3D 11 code. (Source) But there are a lot of intersecting factors at play, and optimizing your GL code might yield bigger speedups than a D3D rewrite in the same amount of time. Stuff like using your buffers properly, batching,  vertex arrays, uniform buffers, texture formats, avoiding slow path GL stuff, etc. There are also driver headaches, but no sense worrying about those unless Intel is really big for you and in that case testing is the correct approach.

Edited by Promit

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Announcements

  • Forum Statistics

    • Total Topics
      628401
    • Total Posts
      2982457
  • Similar Content

    • By test opty
      Hi all,
       
      I'm starting OpenGL using a tut on the Web. But at this point I would like to know the primitives needed for creating a window using OpenGL. So on Windows and using MS VS 2017, what is the simplest code required to render a window with the title of "First Rectangle", please?
       
       
    • By DejayHextrix
      Hi, New here. 
      I need some help. My fiance and I like to play this mobile game online that goes by real time. Her and I are always working but when we have free time we like to play this game. We don't always got time throughout the day to Queue Buildings, troops, Upgrades....etc.... 
      I was told to look into DLL Injection and OpenGL/DirectX Hooking. Is this true? Is this what I need to learn? 
      How do I read the Android files, or modify the files, or get the in-game tags/variables for the game I want? 
      Any assistance on this would be most appreciated. I been everywhere and seems no one knows or is to lazy to help me out. It would be nice to have assistance for once. I don't know what I need to learn. 
      So links of topics I need to learn within the comment section would be SOOOOO.....Helpful. Anything to just get me started. 
      Thanks, 
      Dejay Hextrix 
    • By mellinoe
      Hi all,
      First time poster here, although I've been reading posts here for quite a while. This place has been invaluable for learning graphics programming -- thanks for a great resource!
      Right now, I'm working on a graphics abstraction layer for .NET which supports D3D11, Vulkan, and OpenGL at the moment. I have implemented most of my planned features already, and things are working well. Some remaining features that I am planning are Compute Shaders, and some flavor of read-write shader resources. At the moment, my shaders can just get simple read-only access to a uniform (or constant) buffer, a texture, or a sampler. Unfortunately, I'm having a tough time grasping the distinctions between all of the different kinds of read-write resources that are available. In D3D alone, there seem to be 5 or 6 different kinds of resources with similar but different characteristics. On top of that, I get the impression that some of them are more or less "obsoleted" by the newer kinds, and don't have much of a place in modern code. There seem to be a few pivots:
      The data source/destination (buffer or texture) Read-write or read-only Structured or unstructured (?) Ordered vs unordered (?) These are just my observations based on a lot of MSDN and OpenGL doc reading. For my library, I'm not interested in exposing every possibility to the user -- just trying to find a good "middle-ground" that can be represented cleanly across API's which is good enough for common scenarios.
      Can anyone give a sort of "overview" of the different options, and perhaps compare/contrast the concepts between Direct3D, OpenGL, and Vulkan? I'd also be very interested in hearing how other folks have abstracted these concepts in their libraries.
    • By aejt
      I recently started getting into graphics programming (2nd try, first try was many years ago) and I'm working on a 3d rendering engine which I hope to be able to make a 3D game with sooner or later. I have plenty of C++ experience, but not a lot when it comes to graphics, and while it's definitely going much better this time, I'm having trouble figuring out how assets are usually handled by engines.
      I'm not having trouble with handling the GPU resources, but more so with how the resources should be defined and used in the system (materials, models, etc).
      This is my plan now, I've implemented most of it except for the XML parts and factories and those are the ones I'm not sure of at all:
      I have these classes:
      For GPU resources:
      Geometry: holds and manages everything needed to render a geometry: VAO, VBO, EBO. Texture: holds and manages a texture which is loaded into the GPU. Shader: holds and manages a shader which is loaded into the GPU. For assets relying on GPU resources:
      Material: holds a shader resource, multiple texture resources, as well as uniform settings. Mesh: holds a geometry and a material. Model: holds multiple meshes, possibly in a tree structure to more easily support skinning later on? For handling GPU resources:
      ResourceCache<T>: T can be any resource loaded into the GPU. It owns these resources and only hands out handles to them on request (currently string identifiers are used when requesting handles, but all resources are stored in a vector and each handle only contains resource's index in that vector) Resource<T>: The handles given out from ResourceCache. The handles are reference counted and to get the underlying resource you simply deference like with pointers (*handle).  
      And my plan is to define everything into these XML documents to abstract away files:
      Resources.xml for ref-counted GPU resources (geometry, shaders, textures) Resources are assigned names/ids and resource files, and possibly some attributes (what vertex attributes does this geometry have? what vertex attributes does this shader expect? what uniforms does this shader use? and so on) Are reference counted using ResourceCache<T> Assets.xml for assets using the GPU resources (materials, meshes, models) Assets are not reference counted, but they hold handles to ref-counted resources. References the resources defined in Resources.xml by names/ids. The XMLs are loaded into some structure in memory which is then used for loading the resources/assets using factory classes:
      Factory classes for resources:
      For example, a texture factory could contain the texture definitions from the XML containing data about textures in the game, as well as a cache containing all loaded textures. This means it has mappings from each name/id to a file and when asked to load a texture with a name/id, it can look up its path and use a "BinaryLoader" to either load the file and create the resource directly, or asynchronously load the file's data into a queue which then can be read from later to create the resources synchronously in the GL context. These factories only return handles.
      Factory classes for assets:
      Much like for resources, these classes contain the definitions for the assets they can load. For example, with the definition the MaterialFactory will know which shader, textures and possibly uniform a certain material has, and with the help of TextureFactory and ShaderFactory, it can retrieve handles to the resources it needs (Shader + Textures), setup itself from XML data (uniform values), and return a created instance of requested material. These factories return actual instances, not handles (but the instances contain handles).
       
       
      Is this a good or commonly used approach? Is this going to bite me in the ass later on? Are there other more preferable approaches? Is this outside of the scope of a 3d renderer and should be on the engine side? I'd love to receive and kind of advice or suggestions!
      Thanks!
    • By nedondev
      I 'm learning how to create game by using opengl with c/c++ coding, so here is my fist game. In video description also have game contain in Dropbox. May be I will make it better in future.
      Thanks.
  • Popular Now