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I've heard different things when wondering whether to use DirectX for graphical programs or to use OpenGL. Some people have said that DirectX is more powerful/better but harder to use, is this true?

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This topic again?

http://www.google.com/search?q=opengl+vs+directx

and

http://tinyurl.com/3x6m7e (local search)

Search is a wonderful thing.

Summary? It is up to you, they can both more or less do the same things, and they do them in similar ways for the most part.

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This question springs up a lot and tends to lead to pointless arguments between different camps.

Firstly I'd better point out the more accurate comparison is between OpenGL and Direct3D. DirectX controls a lot more than just the graphics. That isn't necessarily a strike against OpenGL though, as with libraries such as SDL you can get a similar grade of functionality for most games.

I'm not an expert, but I've read a few of these debates. Basically I think the argument comes down to this:
  • If you are aiming for cross-platform games, use OpenGL
  • If you prefer C style procedural programming then OpenGL is more your flavour. If you prefer a more object oriented approach you might prefer Direct3D.
  • OpenGL may be slightly easier to get started in and draw things to the screen, but when you get deep into it then it's roughly the same.
  • If you are undecided about any of these and are developing for Windows it probably doesn't matter which one you choose. Once you are familiar with either OpenGL or Direct3D it's pretty easy to learn the other one.
  • Ideally once you get into a large project you'd write the code so it's not that dependent on what graphical interface you use, so you can easily swap between OpenGL or Direct3D or give your players the choice between the two

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I've worked with both, and OpenGL is a LOT easier to understand and start with. Direct3D is cool when you get it to work, but you got a lot to do before you get it to work like what you want.

But, Direct3D is a lot more powerful than OpenGL. I rarely see professional games in OpenGL, though OpenGL can be used in Linux as well.

I'm a very C style programmer, and only use OOP features when necessary. I also use Dev-C++, which is Linux based, instead of VC++, and OpenGL is the practially the only thing that works on it. This makes me exclusively OpenGL.

Now, I once tried Direct3D with VC++ and was impressed at what it can do, but ultimately I will never go back. It has too much overhead for me, and that constricts me too much. I'm just a 'weekend game programmer', so I'm not looking for flashy cool things. :)

Anyways, I'd say go with OpenGL, but if you want a real professional game, you must learn Direct3D someday. ;)

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hmmm... you signed up to post this, the most commonly asked question of all time. ( I think )

Troll?

Well, in any case, they're both pretty solid. Here's the first result from Google, that site has been known to have excellent articles. Personally I think its best to support both. There are so many cards and so many configurations out there, that who knows what kind of drivers / system setup your end-user will have. If you use an engine like OGRE, it will already include nearly identical support for both DirectX & OpenGL, so that your user can choose which to use and you can focus on other things.

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Quote:
Original post by sykosnakesix
I've worked with both, and OpenGL is a LOT easier to understand and start with. Direct3D is cool when you get it to work, but you got a lot to do before you get it to work like what you want.

But, Direct3D is a lot more powerful than OpenGL. I rarely see professional games in OpenGL, though OpenGL can be used in Linux as well.

I'm a very C style programmer, and only use OOP features when necessary. I also use Dev-C++, which is Linux based, instead of VC++, and OpenGL is the practially the only thing that works on it. This makes me exclusively OpenGL.

Now, I once tried Direct3D with VC++ and was impressed at what it can do, but ultimately I will never go back. It has too much overhead for me, and that constricts me too much. I'm just a 'weekend game programmer', so I'm not looking for flashy cool things. :)

Anyways, I'd say go with OpenGL, but if you want a real professional game, you must learn Direct3D someday. ;)


Odd, i thought doom3 was a professional game.

Also i still havn't seen a single feature in D3D that isn't avaliable in OpenGL. For any platform except Vista OpenGL is the only API that provides full access to the latest hardware. (And it will continue to be the case unless microsoft changes their mind about backporting DX10 to older windows versions , or updating D3D9 yet again.)

Ofcourse you might be refering to something else when you talk about power.

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I think the previous messages give some good advice. For whatever this is worth, I learned DirectX when I took a contract to create the game engine (and the guts of the first game) for a commercial game development company. So I guess it is reasonable to say I understood DirectX pretty well by the time the game was complete and released to market.

A few months ago I had to create the guts of a new 3D engine from scratch, which had to be based upon OpenGL for portability reason. Having gone through a painful learning curve with brand X, I was not thrilled to repeat the learning curve again with brand Y. Anyway, seeing your post made me think my experience might be helpful to your question. But remember, we all have different tastes and reasons for our preferences, so possibly your experience could be opposite mine.

The first week or so was definitely getting used to a new approach to 3D, which is to say, the way they work *is* different - or about as different as they can be given they end up being almost identical, functionally.

However, after the first week, everything thereafter was a major relief! It was like having a thorn removed after you kind of got used to the pain. For me, the difference is that significant. While I know some developers out there might be able to have exactly the opposite experience, it is actually difficult for me to believe it deep inside. Yet I know tastes *are* often that different.

Specifically, when working with the OpenGL API, I find my thinking process is about 3D, graphics, the architecture of my application, things like that. When I work with the DirectX API, I find my thinking process is often about finding or remembering or looking-up arbitrary details - the "how do I get done what I want). It feels like one extra unnecessary level of information to remember and cope with --- which almost seems to vanish with OpenGL.

That was my experience. Depending on your goals and your own preferences (likes and dislikes), your experience could be different, even opposite I suppose (even if that is difficult to imagine from inside my skull).

Oh, one important difference (mentioned by others) is not a matter of taste. If you think you'll ever be creating 3D applications for other platforms, you might want to choose OpenGL now - because then you won't need to subject yourself to a learning curve repeatedly like I did. Actually, it was three times for me (because the first 3D engine I wrote was 100% in my own code with no "helper" API beneath - just linear memory mapped onto the screen).

Good luck.

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If you are definately going to do Windown, Linux and OSX versions then OpenGL uis probably the easier route. Note the definately in that sentance, some dream about maybe one day along the line doing it shouldn't be a consideration imo.

That aside, honestly, give both a try and see which you prefer.
About the only real advantage D3D has right now over OpenGL for the new user is the SDK and related docs, they are pretty good and easy to get hold of.

One more consideration to throw into the mix; OpenGL is changing and soon.

I'm 99% sure that June will see the release of the new spec for OpenGL Longs Peak, this is a major change and while the old OpenGL2.x style programming will of course still work you might want to consider that you'll have to learn a reasonably different set of API functions afterwards to get the best from it.

I'm also given to believe there are some differences between D3D9 and D3D10 as well which means the same more or less applies there; however don't take my word on this as a definative answer as I'm a D3D9 newbie myself [grin]

Quote:

Original post by sykosnakesix
But, Direct3D is a lot more powerful than OpenGL.


This, is wrong.
Both OGL and D3D talk to the same hardware via the same drivers; effectively what one can do the other can do (there are small differences).

The reason why you see less OpenGL based commerical games is due to other factors; mostly based in what was going on in the OGL world a couple of years back based on the speed of OGL change and unresponsiveness of the ARB to change leading to what many termed 'extension hell' where vendor specific paths had to be taken to have access to the latest and greatest features. This has somewhat been fixed in the last couple of years.

As for games which use it; well anything based on the Quake or Doom engine series is ofcourse OpenGL based and I was surprised to find Homeworld 2 was (I knew Homeworld was), however you'd be right saying that many new commerical titles don't use it on Windows at least (WoW for example uses it on the Mac).

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I've not worked extensively with D3D on Win32 platforms, but I have on both Xbox and Xbox 360. My impression of it is that it has a C++ interface, but it's not exactly accurate to call it object oriented. It's really almost as procedural as OpenGL in practice.

The capability comparisons are mostly related to your platform and driver combo than the APIs themselves.

OpenGL's biggest strength and weakness is the "Open" part. It means that hardware manufacturers can add support for new features via extensions without the intervention of another company, but it also has historically meant that things can go for long periods of time without being standardized... leaving you in a situation where you have to implement the same feature in 2-3 different ways (using manufacturer extensions) because nothing has been standarized yet.

I don't know if this is a huge problem today, but it was a pretty big annoyance last time I did OpenGL development (shortly before OpenGL 2.0 was standarized).

So yeah, it really doesn't come down to one API being intrinsically better than the other. It comes down to which you prefer and which runs on the platforms you are targetting. (For all its portability, OpenGL isn't supported on a few significant commercial platforms.)

But this is always framed as a "versus" debate. So I'm going to make the audacious suggestion of learning and using both APIs.

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Quote:
Original post by exwonder
I've not worked extensively with D3D on Win32 platforms, but I have on both Xbox and Xbox 360. My impression of it is that it has a C++ interface, but it's not exactly accurate to call it object oriented. It's really almost as procedural as OpenGL in practice.

The capability comparisons are mostly related to your platform and driver combo than the APIs themselves.

OpenGL's biggest strength and weakness is the "Open" part. It means that hardware manufacturers can add support for new features via extensions without the intervention of another company, but it also has historically meant that things can go for long periods of time without being standardized... leaving you in a situation where you have to implement the same feature in 2-3 different ways (using manufacturer extensions) because nothing has been standarized yet.

I don't know if this is a huge problem today, but it was a pretty big annoyance last time I did OpenGL development (shortly before OpenGL 2.0 was standarized).

So yeah, it really doesn't come down to one API being intrinsically better than the other. It comes down to which you prefer and which runs on the platforms you are targetting. (For all its portability, OpenGL isn't supported on a few significant commercial platforms.)

But this is always framed as a "versus" debate. So I'm going to make the audacious suggestion of learning and using both APIs.


It is a bit better today, but i would still claim that OpenGLs main strengths are extensions and portability, and its greatest weakness is extensions.

Currently we can play with the G80 using nvidias extensions. (We could do that a few months before D3D10 was released even) , ATI/AMD doesn't seem to have any info regarding extensions for the r600 yet though. Thus we cannot know how big a problem it will be for this generation of cards.

The uncertainty is the biggest problem right now imo.
If i write a game in D3D10 i know it will run well on ATI:s next card without any modifications. If i write it in OpenGL using the new nvidia extensions i will possibly have to release a patch to get the same features on ATI hardware.

Ofcourse if i write it in OpenGL i get those features working in win2k/XP, aswell as non microsoft systems, but the number of users with G80:s running those systems are easily counted. (Mostly OpenGL developers who like to play with new shiny features as most gamers belive you need Vista to even use a G80)

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I Thought i should say something about this.

if u would like to learn the same language Down from scratch every 2 year then go for DirectX.

I Learnt the DX7 by my own harwork without any knowledge of graphics programming. then DX8 was realeased and after many days of banging my brain i found Directdraw wasn't there. then i started learning the sprite engine in DX8. and suddenly i came to know there is DX9 with Directdraw. i left my foot and ran for it. by the time i got enough time to get that whacky over 300 MB SDK from internet from my buzy life i found that the DX10 is released and then i again banged my head and stoped chasing MS. i found NEHE and learnt good things about OpenGL. since then no release of DX excites me and i will never think of using DX again. who knows by the time i learn to manage DX10 there will be DX15 in the market.

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This question has been asked too many times already. Really; there should be a sticky for this [smile].

Quote:
DirectX is more powerful/better but harder to use, is this true?

The answer is no. Both graphics APIs are equally difficult to learn. I suggest you learn one (any one) and the other can be picked up very easily. Under the hood both APIs have equivalent functionality. They are more similar than you think. I learnt OpenGL before Direct3D and when it came to picking up Direct3D, it seemed pretty easy to pick up. I don't understand what the fuss is about. Get your 3D/2D concepts clear by learning one. That I think is the most important thing to learning any of the two APIs.

I agree with exwonder, there is no versus debate. Learn one, then pick up the other.

[EDIT]Yup... there is a whole article on this. Almost forgot about that.

[Edited by - _neutrin0_ on April 10, 2007 2:49:46 AM]

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I find OpenGL to be a repulsive, badly designed mess. Others disagree. In the end, it doesn't matter. Any vaguely competent graphics programmer will end up being fluent in both. I think OGL is superficially easier to start with, but D3D becomes much easier once you decide to do anything significant (texturing, for example).

Quote:
I also use Dev-C++, which is Linux based, instead of VC++
Dev-C++ isn't "Linux based". It uses GCC as its compiler, which has nothing to do with Linux. It's also a piece of junk that should be deleted and replaced immediately.

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Quote:
Original post by sykosnakesix
I rarely see professional games in OpenGL, though OpenGL can be used in Linux as well.


All playstation games are made with opengl (probably nintendo consoles too)

Quote:

It's also a piece of junk that should be deleted and replaced immediately.


What's wrong with Dev c++? I've tried the MS ide's and they're horrible (stdfix.h?).

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Quote:
Original post by Promit
I find OpenGL to be a repulsive, badly designed mess. Others disagree. In the end, it doesn't matter. Any vaguely competent graphics programmer will end up being fluent in both. I think OGL is superficially easier to start with, but D3D becomes much easier once you decide to do anything significant (texturing, for example).


Agreed. When OGL 2.0 was around the corner, I was hoping that the situation would radically improve. It did not. For example, FBOs still don't work with anti-aliasing (EXT_framebuffer_multisample is *still* not publically available). Now, when I complain, people tell me that OGL 3.0 will fix those issues.. sorry, but I'm tired of waiting. Unfortunately I have too much code to switch to D3D9/D3D10, so for the moment I'm sticking to OGL..

Y.

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Quote:
Original post by Death100
Quote:
Original post by sykosnakesix
I rarely see professional games in OpenGL, though OpenGL can be used in Linux as well.


All playstation games are made with opengl (probably nintendo consoles too)
Only PS3 games, and OGL|ES, not OGL. No other console uses OGL, though some of the APIs resemble it.

Quote:

What's wrong with Dev c++? I've tried the MS ide's and they're horrible (stdfix.h?).
Please. You don't even know enough about VC to remember the name of the thing you're trying to complain about.

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I can't compare OpenGL with DirectX since I never really used DirectX. But does it really makes a difference?

Nowadays most of the special effects and optimizing, heavily depends on the video-card hardware (shaders, using VBO's, and so on). 5 years ago you needed much knowledge about your API to make nice special effects (making water, reflections, and so on), but now you can do most of the work inside the shader code. Unless you choose GLSL or <what's the equivalent for DX?>, this won't have much to do with the API you're using.

OpenGL/DirectX just passes the data, and provides some buffers/textures. Maybe that's not 100% true, but I certainly feel most of the focus now lies on shaders and the video-card hardware, instead of the more advanced functions inside OpenGL or DirectX. Of course, you still need to know how to make a VBO or FBO in both API's when doing the more advanced stuff, but that has not much to do with performance, only the coding style you prefer.

greetings,
Rick

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For those of you that know OpenGL very well, is there a way to share OpenGL resources like textures, vertex buffers, etc. between multiple processes like I can with D3D9Ex?

I don't want to have to create and initialize the same resource across multiple processes and would rather do it once and just pass a handle around.

Can I do this sort of thing when using OpenGL?

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Quote:
What's wrong with Dev c++? I've tried the MS ide's and they're horrible (stdfix.h?).


You do know that you can create an empty project that does not include the extra stuff for precompiled headers right?

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Quote:
Original post by don
For those of you that know OpenGL very well, is there a way to share OpenGL resources like textures, vertex buffers, etc. between multiple processes like I can with D3D9Ex?

Yes, i haven't used it myself but i know it's there.

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Honestly, I'm new at most of this. I've read many of Nehe's tutorials so I can do some stuff in OpenGL if I set my mind on it, but I really haven't actually finished anything. I just don't want to spend the time to learn one of them, only to find out that the other is better, etc. So what I understand is they're both basically the same in difficulty and functionality in the long run. But as for Dev-C++ it is the compiler I am using as well. Does someone have a suggestion for a better one?

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Quote:
Original post by GMX
But as for Dev-C++ it is the compiler I am using as well. Does someone have a suggestion for a better one?

Visual Studio 2005 Standard Edition, or if you can't or won't get that, then the Express Edition. I've been using the Standard Edition I got for free last year, and I definitely enjoy it. Perhaps it takes a bit of time to get use to it, but I've been using various versions of Visual Studio for a long time, so VS2005 was simply similar but better.

It sort of reminds me of a similar thing with OGL/D3D, where with OGL it takes very little code and comprehension to get something on the screen, but it takes a bit more code and comprehension to do the same with D3D. Similarly, some IDEs might make it easier to quickly build a very basic program from a single source file, but VS2005 is very nice when working with any project of a more command and realistic size.

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One thing to be aware of. Video card manufacturers tend to focus on their Direct3D drivers before their OpenGL ones. Not a problem with ATI or NVIDIA, but I've had the dubious honour of trying to develop a modern OpenGL renderer on Intel accelerators of which there are a hell of a lot of out there. Their OpenGL implementation is bad.

They only support OpenGL 1.4 so no GLSL despite having pixel shader 2.0 hardware. Non-power-of-two textures are not supported (yet are in their Direct3D drivers). Render-to-texture is buggy and uses the old pbuffer system. Using auto-mipmapping caused driver crashes. And this from their latest drivers as of two months ago.

Unless you're planning on cross-platform support, just stick with Direct3D. As much as I love OpenGL, its poor support and its terrible render-to-texture system that has only just been fixed but not before holding back the API for years (something over which John Carmack once said almost made him switch to D3D), simply make it hard for me to recommend for a big project.

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      Creating Shaders
      While in earlier APIs shaders were bound separately, in the next-generation APIs as well as in Diligent Engine shaders are part of the pipeline state object. The biggest challenge when authoring shaders is that Direct3D and OpenGL/Vulkan use different shader languages (while Apple uses yet another language in their Metal API). Maintaining two versions of every shader is not an option for real applications and Diligent Engine implements shader source code converter that allows shaders authored in HLSL to be translated to GLSL. To create a shader, one needs to populate ShaderCreationAttribs structure. SourceLanguage member of this structure tells the system which language the shader is authored in:
      SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source language matches the underlying graphics API: HLSL for Direct3D11/Direct3D12 mode, and GLSL for OpenGL and OpenGLES modes. SHADER_SOURCE_LANGUAGE_HLSL - The shader source is in HLSL. For OpenGL and OpenGLES modes, the source code will be converted to GLSL. SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL. There is currently no GLSL to HLSL converter, so this value should only be used for OpenGL and OpenGLES modes. There are two ways to provide the shader source code. The first way is to use Source member. The second way is to provide a file path in FilePath member. Since the engine is entirely decoupled from the platform and the host file system is platform-dependent, the structure exposes pShaderSourceStreamFactory member that is intended to provide the engine access to the file system. If FilePath is provided, shader source factory must also be provided. If the shader source contains any #include directives, the source stream factory will also be used to load these files. The engine provides default implementation for every supported platform that should be sufficient in most cases. Custom implementation can be provided when needed.
      When sampling a texture in a shader, the texture sampler was traditionally specified as separate object that was bound to the pipeline at run time or set as part of the texture object itself. However, in most cases it is known beforehand what kind of sampler will be used in the shader. Next-generation APIs expose new type of sampler called static sampler that can be initialized directly in the pipeline state. Diligent Engine exposes this functionality: when creating a shader, textures can be assigned static samplers. If static sampler is assigned, it will always be used instead of the one initialized in the texture shader resource view. To initialize static samplers, prepare an array of StaticSamplerDesc structures and initialize StaticSamplers and NumStaticSamplers members. Static samplers are more efficient and it is highly recommended to use them whenever possible. On older APIs, static samplers are emulated via generic sampler objects.
      The following is an example of shader initialization:
      ShaderCreationAttribs Attrs; Attrs.Desc.Name = "MyPixelShader"; Attrs.FilePath = "MyShaderFile.fx"; Attrs.SearchDirectories = "shaders;shaders\\inc;"; Attrs.EntryPoint = "MyPixelShader"; Attrs.Desc.ShaderType = SHADER_TYPE_PIXEL; Attrs.SourceLanguage = SHADER_SOURCE_LANGUAGE_HLSL; BasicShaderSourceStreamFactory BasicSSSFactory(Attrs.SearchDirectories); Attrs.pShaderSourceStreamFactory = &BasicSSSFactory; ShaderVariableDesc ShaderVars[] = {     {"g_StaticTexture", SHADER_VARIABLE_TYPE_STATIC},     {"g_MutableTexture", SHADER_VARIABLE_TYPE_MUTABLE},     {"g_DynamicTexture", SHADER_VARIABLE_TYPE_DYNAMIC} }; Attrs.Desc.VariableDesc = ShaderVars; Attrs.Desc.NumVariables = _countof(ShaderVars); Attrs.Desc.DefaultVariableType = SHADER_VARIABLE_TYPE_STATIC; StaticSamplerDesc StaticSampler; StaticSampler.Desc.MinFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MagFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MipFilter = FILTER_TYPE_LINEAR; StaticSampler.TextureName = "g_MutableTexture"; Attrs.Desc.NumStaticSamplers = 1; Attrs.Desc.StaticSamplers = &StaticSampler; ShaderMacroHelper Macros; Macros.AddShaderMacro("USE_SHADOWS", 1); Macros.AddShaderMacro("NUM_SHADOW_SAMPLES", 4); Macros.Finalize(); Attrs.Macros = Macros; RefCntAutoPtr<IShader> pShader; m_pDevice->CreateShader( Attrs, &pShader );
      Creating the Pipeline State Object
      After all required shaders are created, the rest of the fields of the PipelineStateDesc structure provide depth-stencil, rasterizer, and blend state descriptions, the number and format of render targets, input layout format, etc. For instance, rasterizer state can be described as follows:
      PipelineStateDesc PSODesc; RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; RasterizerDesc.AntialiasedLineEnable = False; Depth-stencil and blend states are defined in a similar fashion.
      Another important thing that pipeline state object encompasses is the input layout description that defines how inputs to the vertex shader, which is the very first shader stage, should be read from the memory. Input layout may define several vertex streams that contain values of different formats and sizes:
      // Define input layout InputLayoutDesc &Layout = PSODesc.GraphicsPipeline.InputLayout; LayoutElement TextLayoutElems[] = {     LayoutElement( 0, 0, 3, VT_FLOAT32, False ),     LayoutElement( 1, 0, 4, VT_UINT8, True ),     LayoutElement( 2, 0, 2, VT_FLOAT32, False ), }; Layout.LayoutElements = TextLayoutElems; Layout.NumElements = _countof( TextLayoutElems ); Finally, pipeline state defines primitive topology type. When all required members are initialized, a pipeline state object can be created by IRenderDevice::CreatePipelineState() method:
      // Define shader and primitive topology PSODesc.GraphicsPipeline.PrimitiveTopologyType = PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE; PSODesc.GraphicsPipeline.pVS = pVertexShader; PSODesc.GraphicsPipeline.pPS = pPixelShader; PSODesc.Name = "My pipeline state"; m_pDev->CreatePipelineState(PSODesc, &m_pPSO); When PSO object is bound to the pipeline, the engine invokes all API-specific commands to set all states specified by the object. In case of Direct3D12 this maps directly to setting the D3D12 PSO object. In case of Direct3D11, this involves setting individual state objects (such as rasterizer and blend states), shaders, input layout etc. In case of OpenGL, this requires a number of fine-grain state tweaking calls. Diligent Engine keeps track of currently bound states and only calls functions to update these states that have actually changed.
      Binding Shader Resources
      Direct3D11 and OpenGL utilize fine-grain resource binding models, where an application binds individual buffers and textures to certain shader or program resource binding slots. Direct3D12 uses a very different approach, where resource descriptors are grouped into tables, and an application can bind all resources in the table at once by setting the table in the command list. Resource binding model in Diligent Engine is designed to leverage this new method. It introduces a new object called shader resource binding that encapsulates all resource bindings required for all shaders in a certain pipeline state. It also introduces the classification of shader variables based on the frequency of expected change that helps the engine group them into tables under the hood:
      Static variables (SHADER_VARIABLE_TYPE_STATIC) are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers. Mutable variables (SHADER_VARIABLE_TYPE_MUTABLE) define resources that are expected to change on a per-material frequency. Examples may include diffuse textures, normal maps etc. Dynamic variables (SHADER_VARIABLE_TYPE_DYNAMIC) are expected to change frequently and randomly. Shader variable type must be specified during shader creation by populating an array of ShaderVariableDesc structures and initializing ShaderCreationAttribs::Desc::VariableDesc and ShaderCreationAttribs::Desc::NumVariables members (see example of shader creation above).
      Static variables cannot be changed once a resource is bound to the variable. They are bound directly to the shader object. For instance, a shadow map texture is not expected to change after it is created, so it can be bound directly to the shader:
      PixelShader->GetShaderVariable( "g_tex2DShadowMap" )->Set( pShadowMapSRV ); Mutable and dynamic variables are bound via a new Shader Resource Binding object (SRB) that is created by the pipeline state (IPipelineState::CreateShaderResourceBinding()):
      m_pPSO->CreateShaderResourceBinding(&m_pSRB); Note that an SRB is only compatible with the pipeline state it was created from. SRB object inherits all static bindings from shaders in the pipeline, but is not allowed to change them.
      Mutable resources can only be set once for every instance of a shader resource binding. Such resources are intended to define specific material properties. For instance, a diffuse texture for a specific material is not expected to change once the material is defined and can be set right after the SRB object has been created:
      m_pSRB->GetVariable(SHADER_TYPE_PIXEL, "tex2DDiffuse")->Set(pDiffuseTexSRV); In some cases it is necessary to bind a new resource to a variable every time a draw command is invoked. Such variables should be labeled as dynamic, which will allow setting them multiple times through the same SRB object:
      m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); Under the hood, the engine pre-allocates descriptor tables for static and mutable resources when an SRB objcet is created. Space for dynamic resources is dynamically allocated at run time. Static and mutable resources are thus more efficient and should be used whenever possible.
      As you can see, Diligent Engine does not expose low-level details of how resources are bound to shader variables. One reason for this is that these details are very different for various APIs. The other reason is that using low-level binding methods is extremely error-prone: it is very easy to forget to bind some resource, or bind incorrect resource such as bind a buffer to the variable that is in fact a texture, especially during shader development when everything changes fast. Diligent Engine instead relies on shader reflection system to automatically query the list of all shader variables. Grouping variables based on three types mentioned above allows the engine to create optimized layout and take heavy lifting of matching resources to API-specific resource location, register or descriptor in the table.
      This post gives more details about the resource binding model in Diligent Engine.
      Setting the Pipeline State and Committing Shader Resources
      Before any draw or compute command can be invoked, the pipeline state needs to be bound to the context:
      m_pContext->SetPipelineState(m_pPSO); Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.
      The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
      m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
      Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
      m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
      Invoking Draw Command
      The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
      ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // Set vertex and index buffers IBuffer *buffer[] = {m_pVertexBuffer}; Uint32 offsets[] = {0}; Uint32 strides[] = {sizeof(MyVertex)}; m_pContext->SetVertexBuffers(0, 1, buffer, strides, offsets, SET_VERTEX_BUFFERS_FLAG_RESET); m_pContext->SetIndexBuffer(m_pIndexBuffer, 0); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:
      DrawAttribs attrs; attrs.IsIndexed = true; attrs.IndexType = VT_UINT16; attrs.NumIndices = 36; attrs.Topology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST; pContext->Draw(attrs); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
      Source Code
      Full engine source code is available on GitHub and is free to use. The repository contains tutorials, sample applications, asteroids performance benchmark and an example Unity project that uses Diligent Engine in native plugin.
      Atmospheric scattering sample demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

      Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

      Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

      Future Work
      The engine is under active development. It currently supports Windows desktop, Universal Windows, Linux, Android, MacOS, and iOS platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and Metal backend is in the plan.
    • By LifeArtist
      Good Evening,
      I want to make a 2D game which involves displaying some debug information. Especially for collision, enemy sights and so on ...
      First of I was thinking about all those shapes which I need will need for debugging purposes: circles, rectangles, lines, polygons.
      I am really stucked right now because of the fundamental question:
      Where do I store my vertices positions for each line (object)? Currently I am not using a model matrix because I am using orthographic projection and set the final position within the VBO. That means that if I add a new line I would have to expand the "points" array and re-upload (recall glBufferData) it every time. The other method would be to use a model matrix and a fixed vbo for a line but it would be also messy to exactly create a line from (0,0) to (100,20) calculating the rotation and scale to make it fit.
      If I proceed with option 1 "updating the array each frame" I was thinking of having 4 draw calls every frame for the lines vao, polygons vao and so on. 
      In addition to that I am planning to use some sort of ECS based architecture. So the other question would be:
      Should I treat those debug objects as entities/components?
      For me it would make sense to treat them as entities but that's creates a new issue with the previous array approach because it would have for example a transform and render component. A special render component for debug objects (no texture etc) ... For me the transform component is also just a matrix but how would I then define a line?
      Treating them as components would'nt be a good idea in my eyes because then I would always need an entity. Well entity is just an id !? So maybe its a component?
      Regards,
      LifeArtist
    • By QQemka
      Hello. I am coding a small thingy in my spare time. All i want to achieve is to load a heightmap (as the lowest possible walking terrain), some static meshes (elements of the environment) and a dynamic character (meaning i can move, collide with heightmap/static meshes and hold a varying item in a hand ). Got a bunch of questions, or rather problems i can't find solution to myself. Nearly all are deal with graphics/gpu, not the coding part. My c++ is on high enough level.
      Let's go:
      Heightmap - i obviously want it to be textured, size is hardcoded to 256x256 squares. I can't have one huge texture stretched over entire terrain cause every pixel would be enormous. Thats why i decided to use 2 specified textures. First will be a tileset consisting of 16 square tiles (u v range from 0 to 0.25 for first tile and so on) and second a 256x256 buffer with 0-15 value representing index of the tile from tileset for every heigtmap square. Problem is, how do i blend the edges nicely and make some computationally cheap changes so its not obvious there are only 16 tiles? Is it possible to generate such terrain with some existing program?
      Collisions - i want to use bounding sphere and aabb. But should i store them for a model or entity instance? Meaning i have 20 same trees spawned using the same tree model, but every entity got its own transformation (position, scale etc). Storing collision component per instance grats faster access + is precalculated and transformed (takes additional memory, but who cares?), so i stick with this, right? What should i do if object is dynamically rotated? The aabb is no longer aligned and calculating per vertex min/max everytime object rotates/scales is pretty expensive, right?
      Drawing aabb - problem similar to above (storing aabb data per instance or model). This time in my opinion per model is enough since every instance also does not have own vertex buffer but uses the shared one (so 20 trees share reference to one tree model). So rendering aabb is about taking the model's aabb, transforming with instance matrix and voila. What about aabb vertex buffer (this is more of a cosmetic question, just curious, bumped onto it in time of writing this). Is it better to make it as 8 points and index buffer (12 lines), or only 2 vertices with min/max x/y/z and having the shaders dynamically generate 6 other vertices and draw the box? Or maybe there should be just ONE 1x1x1 cube box template moved/scaled per entity?
      What if one model got a diffuse texture and a normal map, and other has only diffuse? Should i pass some bool flag to shader with that info, or just assume that my game supports only diffuse maps without fancy stuff?
      There were several more but i forgot/solved them at time of writing
      Thanks in advance
    • By RenanRR
      Hi All,
      I'm reading the tutorials from learnOpengl site (nice site) and I'm having a question on the camera (https://learnopengl.com/Getting-started/Camera).
      I always saw the camera being manipulated with the lookat, but in tutorial I saw the camera being changed through the MVP arrays, which do not seem to be camera, but rather the scene that changes:
      Vertex Shader:
      #version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec2 aTexCoord; out vec2 TexCoord; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { gl_Position = projection * view * model * vec4(aPos, 1.0f); TexCoord = vec2(aTexCoord.x, aTexCoord.y); } then, the matrix manipulated:
      ..... glm::mat4 projection = glm::perspective(glm::radians(fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); ourShader.setMat4("projection", projection); .... glm::mat4 view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp); ourShader.setMat4("view", view); .... model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f)); ourShader.setMat4("model", model);  
      So, some doubts:
      - Why use it like that?
      - Is it okay to manipulate the camera that way?
      -in this way, are not the vertex's positions that changes instead of the camera?
      - I need to pass MVP to all shaders of object in my scenes ?
       
      What it seems, is that the camera stands still and the scenery that changes...
      it's right?
       
       
      Thank you
       
    • By dpadam450
      Sampling a floating point texture where the alpha channel holds 4-bytes of packed data into the float. I don't know how to cast the raw memory to treat it as an integer so I can perform bit-shifting operations.

      int rgbValue = int(textureSample.w);//4 bytes of data packed as color
      // algorithm might not be correct and endianness might need switching.
      vec3 extractedData = vec3(  rgbValue & 0xFF000000,  (rgbValue << 8) & 0xFF000000, (rgbValue << 16) & 0xFF000000);
      extractedData /= 255.0f;
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