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Hello everyone, I'm fairly new to using OpenGL (and game development in general, actually), and I have a few questios. I know this post would be better off in the Beginners forum, but I feel that more experienced people will be able to answer fastrer :D Anyway, here's my questions list: 1) In the OpenGL forum FAQ, there are links given to the BlueBook, and the RedBook. The BlueBook link doesn't work anymore, and the RedBook links to a manual for version 1.0 ...so, does anyone know where I could find updated versions of these two books? 2) I'm actually trying to develop a game with graphics close to commercial quality, so...I think i should use something past OpenGL 1.1 (I'm developing on a Windows XP). What would be a good manual (besides the one provided in the "Game Programming: Tricks of teh Trade" book)? 3) Are there any benefits in developing OpenGL games on a non-Windows platform? Like, getting the latest libraries or something? 4) Does anyone have a sample code to get me started with using OpenGL? (Yeah, I know there's NeHe's tutorials, but I think they're a bit outdated....but then again, I'm fairly new to this, so I just might be talking out of my ass here) Thanks in advance.

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Original post by celestis_genesis
Hello everyone,

I'm fairly new to using OpenGL (and game development in general, actually), and I have a few questios. I know this post would be better off in the Beginners forum, but I feel that more experienced people will be able to answer fastrer :D

Posting questions in the wrong forum for your own convenience will make people ignore and/or flame you. Fair warning. I won't move your post this time, since a couple of these questions aren't quite "For Beginners"-level.
Quote:

1) In the OpenGL forum FAQ, there are links given to the BlueBook, and the RedBook. The BlueBook link doesn't work anymore, and the RedBook links to a manual for version 1.0 ...so, does anyone know where I could find updated versions of these two books?

They are, as their names imply, books. Try your local Barnes & Noble.
Quote:

2) I'm actually trying to develop a game with graphics close to commercial quality, so...I think i should use something past OpenGL 1.1 (I'm developing on a Windows XP). What would be a good manual (besides the one provided in the "Game Programming: Tricks of teh Trade" book)?

You should try clicking that "Books" link up at the top of the page.
Quote:

3) Are there any benefits in developing OpenGL games on a non-Windows platform? Like, getting the latest libraries or something?

Not particularly. Some graphics card manufacturers, such as SGI, release extensions that are not in the main core, but since they aren't widely available on consumer machines, they aren't particularly useful.
Quote:

4) Does anyone have a sample code to get me started with using OpenGL? (Yeah, I know there's NeHe's tutorials, but I think they're a bit outdated....but then again, I'm fairly new to this, so I just might be talking out of my ass here)

You're talking out of your ass. OpenGL is a much more stable API than Direct3D; the tutorials most likely will not be outdated.

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1) I haven't updated my bookmarks too recently, but both the Blue and Red books are in the 4th edition for OpenGL version 1.4, in case you didn't already know. A google search usually comes up with a few free online copies.

2) I'm not current on OpenGL books. I've been doing a lot more DirectX lately myself. I do know that Tricks of the trade is pretty good. Maybe someone else can recommend some other material for reference.

3) Haven't done much cross-platform programming, and I'm not sure I understand the question. Sorry.

4) Actually, NeHe would still be a great way to start, and even if you get through it quickly it's a good way to refine the basics. No matter how outdated a spinning triangle seems compared to the latest graphics engines, you always have to start with a blank window.

Good luck. I wish I could give you more information.

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Original post by celestis_genesis
Hello everyone,


Hi.

Quote:

1) In the OpenGL forum FAQ, there are links given to the BlueBook, and the RedBook. The BlueBook link doesn't work anymore, and the RedBook links to a manual for version 1.0 ...so, does anyone know where I could find updated versions of these two books?


A google query would have solved this. Here are some links that I found:
http://www.opengl.org/documentation/blue_book_1.0/
http://www.amazon.com/exec/obidos/tg/detail/-/0201657651/ref=pd_sxp_f/103-0550504-2139847?v=glance&s=books

I don't own the blue book, so I can't comment on it. However, the red book is a very good resource if you're using OpenGL.
There is yet another book, The OpenGL Shading Language. It is a very thorough reference for glsl. I would not recommend this book until you are very familiar with OpenGL.

Quote:

2) I'm actually trying to develop a game with graphics close to commercial quality, so...I think i should use something past OpenGL 1.1 (I'm developing on a Windows XP). What would be a good manual (besides the one provided in the "Game Programming: Tricks of teh Trade" book)?


The quality of the graphics do not essentially depend on which version of OpenGL you are using. In my opinion, it's got more to do with the quality of the game content.
Newer versions of OpenGL allow for a lot of functionality which can prove useful. You can still access this functionality through OpenGL extensions.

Quote:

3) Are there any benefits in developing OpenGL games on a non-Windows platform? Like, getting the latest libraries or something?


Not quite. You would probably have to access new functionality through extensions anyway.

Quote:

4) Does anyone have a sample code to get me started with using OpenGL? (Yeah, I know there's NeHe's tutorials, but I think they're a bit outdated....but then again, I'm fairly new to this, so I just might be talking out of my ass here)


I learned OpenGL from NeHe. It is a very good resource for beginning OpenGL.
Also, I recommend the OpenGL Programming Guide ("the red book").

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I'm fairly new to using OpenGL (and game development in general, actually


Quote:
I'm actually trying to develop a game with graphics close to commercial quality, so...


ERROR
ERROR

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Your post sound like you want to start programming OpenGL without even learning the basics, just go with the advanced stuff.
That definitelly won't happen :-) A lot of people think they want to skip the basic stuff and just work on a commercial game product (including me when I was learning OpenGL :-). But take my suggestion and start with the basics at NeHe.
The tutorials are NOT outdated, as said earlier, OpenGL is a stable API. Furthermore, you won't have anything other than OpenGL 1.1 on a normal Windows PC - even with Windows XP. It's the Gfx Drivers, that add several extensions to the standard 1.1 API but read more about this on NeHe ;-) But keep in mind, that OpenGL is all based on extensions, while DirectX usually is available in a whole new release as soon as important features are added to new Hardware.

Starting with OpenGL is a good choice, though. I find the OpenGL API being more straight forward than Direct3D, though, when you're familiar with OpenGL it's not so hard anymore, to switch to Direct3D and vice versa, though the other way round might be more difficult for a beginner...

As said earlier in this thread, the reference books are available in newer versions. You might want to buy them and hold a "real copy" in your hands or just download them over the net. They are free and available from various sources: Use google on this!

So now: Go to NeHe's page and start off, putting your idea into code ;-)

Hope this helps...
ZMaster

EDIT: Sorry forgot... Here's something to read for you:
Ultimate Gameprogramming
Gametutorials

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NeHe definatly. Just start on the easy tutorials and work upwards. Some good sites are also:

Game Tutorials
(Unfortunatly it was a lot better when the tuts were free)

Ultimate Game Programming

EDIT: Make sure you are up to scratch with C++, otherwise you will be in a whole new world of s**t.

Quote:
Original post by ZMaster

EDIT: Sorry forgot... Here's something to read for you:
Ultimate Gameprogramming
Gametutorials


Bumgrapes.

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How about starting OpenGL 1.5 + GLSL on Linux and Windows? I'm especially interested in Linux.

Where can I find OGL headers and OGL precompiled libraries, samples, tutorials, etc. Also I have ATI card.


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Original post by NamelessTwo
I'm especially interested in Linux.

Where can I find OGL headers and OGL precompiled libraries, samples, tutorials, etc. Also I have ATI card.


It would depend on your distribution. Usually the OpenGL and GLU headers are installed in /usr/include/GL. If you're running X, then it's likely that they're installed. In Debian, for instance, the headers are included in the xlibmesa-gl-dev and xlibmesa-glu-dev packages.
Otherwise, the ATI drivers should install the necessary libraries and headers.

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Original post by James Trotter
It would depend on your distribution. Usually the OpenGL and GLU headers are installed in /usr/include/GL. If you're running X, then it's likely that they're installed. In Debian, for instance, the headers are included in the xlibmesa-gl-dev and xlibmesa-glu-dev packages.
Otherwise, the ATI drivers should install the necessary libraries and headers.


About the header files: I don't think they are part of the driver. As with windows, the drivers only overwrite your gl libraries. This can be especially annoying on linux distributions which come with bad headers (such as my old Red Hat 7.2 distribution). You can solve that by overwriting the gl headers with the MESA headers, or by using GLEW. I would recommend GLEW, as it is a perfect tool for creating platform-independant OpenGL programs (especially if you use the latest extensions).

Tom

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As far as I know, GLEW doesn't actually let you write platform-independent OpenGL programs in itself. It allows for cross-platform means of using OpenGL extensions. You might have meant GLFW, which is a framework for writing cross-platform OpenGL applications. (However, if you're new to OpenGL I'd recommend you use GLUT instead. This is what they use for the code examples in the red book.)

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Original post by James Trotter
As far as I know, GLEW doesn't actually let you write platform-independent OpenGL programs in itself. It allows for cross-platform means of using OpenGL extensions. You might have meant GLFW, which is a framework for writing cross-platform OpenGL applications. (However, if you're new to OpenGL I'd recommend you use GLUT instead. This is what they use for the code examples in the red book.)


That is correct. My wording was rather ackward. What I meant to say, was that it allows platform independant access to the GL library and extensions. Of course, for os-dependant things like creating windows, you could use glut.

Tom

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Guest Anonymous Poster
Quote:
Original post by James Trotter
Quote:
Original post by NamelessTwo
I'm especially interested in Linux.

Where can I find OGL headers and OGL precompiled libraries, samples, tutorials, etc. Also I have ATI card.


It would depend on your distribution. Usually the OpenGL and GLU headers are installed in /usr/include/GL. If you're running X, then it's likely that they're installed. In Debian, for instance, the headers are included in the xlibmesa-gl-dev and xlibmesa-glu-dev packages.
Otherwise, the ATI drivers should install the necessary libraries and headers.


I use Ubuntu and it comes with Mesa 5 which does not support OGL 1.5 but I intend to compile Mesa 6. Is it possible to install Mesa locally just for the program I develop or I have to replace the original Mesa? I want to do this so that the end user does not need to update his Mesa.

What is GLEW? Does it replace gl.h and glu.h and the appropriate libraries?

Where can I find OpenGL 1.5 headers for Windows?

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Original post by James Trotter
As far as I know, GLEW doesn't actually let you write platform-independent OpenGL programs in itself. It allows for cross-platform means of using OpenGL extensions. You might have meant GLFW, which is a framework for writing cross-platform OpenGL applications. (However, if you're new to OpenGL I'd recommend you use GLUT instead. This is what they use for the code examples in the red book.)


For better crossplatform compatability I'll use SDL - OpenGL, SDL, GLSL and standard C++ libraries only.

I have lots of books and tutorials about OpenGL but none explain how to use the latest versions and GLSL on ATI hardware. That's why I'm asking here.

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Original post by Anonymous Poster
I use Ubuntu and it comes with Mesa 5 which does not support OGL 1.5 but I intend to compile Mesa 6. Is it possible to install Mesa locally just for the program I develop or I have to replace the original Mesa? I want to do this so that the end user does not need to update his Mesa.


I use Ubuntu too. [smile]
If the mesa library uses shared linking, then it has to be available on the system running your programs. If it is statically linked, however, then all the symbols should be included in the executable you compile on your system.

Quote:

What is GLEW? Does it replace gl.h and glu.h and the appropriate libraries?


Not exactly. It does not replace gl.h and glu.h, but it does provide definitions and entry points for functions defined in the OpenGL specification not otherwise available. In other words, it allows you to use OpenGL 2.0. But, of course, only if your graphics card supports the necessary extensions.

Quote:

Where can I find OpenGL 1.5 headers for Windows?


GLEW is cross-platform, and works just as well in Windows as in Linux. (I've tried them both myself!)

Quote:
Original post by NamelessTwo
For better crossplatform compatability I'll use SDL - OpenGL, SDL, GLSL and standard C++ libraries only.


SDL also allows you to create cross-platform OpenGL applications. Though, personally I prefer GLFW or glut. SDL is really more than just a windowing framework, and provides alot of unnecessary functionality for my needs. Although it certainly is cool that it provides you with functionality for audio, CD-rom, timers, threads, and probably more.

Quote:

I have lots of books and tutorials about OpenGL but none explain how to use the latest versions and GLSL on ATI hardware. That's why I'm asking here.


I'm pretty sure you need to access glsl functionality through extensions, (ARB_shading_language_100, ARB_shader_objects).
That at least goes for OpenGL's interface to glsl programs. You can write glsl code independently, as it's a language of its own.

[Edited by - James Trotter on July 6, 2005 2:01:22 PM]

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Thank you for your extensive reply!

Quote:

Not exactly. It does not replace gl.h and glu.h, but it does provide definitions and entry points for functions defined in the OpenGL specification not otherwise available. In other words, it allows you to use OpenGL 2.0. But, of course, only if your graphics card supports the necessary extensions.


So I've found this tutorial:
[url]http://www.lighthouse3d.com/opengl/glsl/index.php?ogloverview[/url]
It describes how to setup OpenGL with GLEW and glut.

I think that current ATI drivers support OpenGL 1.5 only. Probably both on Windows and Linux.
Would I be able to use OpenGL 1.5 functionality with GLEW? I've also checked GLEE but I don't see the difference.

In case I have OpenGL 2.0 compatible driver and MESA 5.0 (which supports only... I don't know what version but it isn't greater than 1.4 for sure), could I use OpenGL 2.0 functionality with GLEW?

Are there any other GLEW tutorials for beginners?

Quote:

Quote:

I have lots of books and tutorials about OpenGL but none explain how to use the latest versions and GLSL on ATI hardware. That's why I'm asking here.


I'm pretty sure you need to access glsl functionality through extensions, (ARB_shading_language_100, ARB_shader_objects).
That at least goes for OpenGL's interface to glsl programs. You can write glsl code independently, as it's a language of its own.



Yes that is true.

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Original post by NamelessTwo
Thank you for your extensive reply!

I think that current ATI drivers support OpenGL 1.5 only. Probably both on Windows and Linux.
Would I be able to use OpenGL 1.5 functionality with GLEW? I've also checked GLEE but I don't see the difference.


I have never used GLEE, so I'm not certain. Though, I do think it generates definitions and entry points for OpenGL extensions automatically from the their specifications, like GLEW does. Someone here should be able to verify/correct this.

Quote:

In case I have OpenGL 2.0 compatible driver and MESA 5.0 (which supports only... I don't know what version but it isn't greater than 1.4 for sure), could I use OpenGL 2.0 functionality with GLEW?


I hope you realize that mesa does not benefit from hardware acceleration. If your drivers support it you should be able to use OpenGL 2.0 functionality. To check this, do something like:


if (GLEW_VERSION_2_0) {
// Use OpenGL 2.0 code...
} else if (GLEW_ARB_shading_language_100) {
// We can't use OpenGL 2.0, so use the ARB_shading_language_100 extension instead...
}


Quote:

Are there any other GLEW tutorials for beginners?


GLEW is extremely simple to use. All you should need to know is explained under GLEW basic usage.

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I hope you realize that mesa does not benefit from hardware acceleration. If your drivers support it you should be able to use OpenGL 2.0 functionality. To check this, do something like:


I mean the OpenGL headers in Ubuntu are those from the MESA library.

Quote:


GLEW is extremely simple to use. All you should need to know is explained under GLEW basic usage.


Sometimes I'm blind and stupid. I've been reading this page and I haven't seen this link! Horrible!

Thank you you've helped me a lot. I'm going to try it soon. I'll do a little bit more research & reading before I start. I think you've cleared alot of things for me.

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Original post by NamelessTwo
Quote:

I hope you realize that mesa does not benefit from hardware acceleration. If your drivers support it you should be able to use OpenGL 2.0 functionality. To check this, do something like:


I mean the OpenGL headers in Ubuntu are those from the MESA library.



Ah, yes. I'm sorry, I misunderstood. You can actually use GLEW to access the functionality of OpenGL 2.0 (or any other version for that matter), regardless of the OpenGL headers installed on the system. I'm pretty certain that when you include glew.h. it takes care of defining all the things which are usually in gl.h. You don't actually include gl.h at all.

Quote:

Thank you you've helped me a lot. I'm going to try it soon. I'll do a little bit more research & reading before I start. I think you've cleared alot of things for me.


I'm glad I could help. [smile]

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      Next-generation APIs allow fine level-control over how resources are allocated. Diligent Engine does not currently expose this functionality, but it can be added by implementing IResourceAllocator interface that encapsulates specifics of resource allocation and providing this interface to CreateBuffer() or CreateTexture() methods. If null is provided, default allocator should be used.
      Initializing the Pipeline State
      As it was mentioned earlier, Diligent Engine follows next-gen APIs to configure the graphics/compute pipeline. One big Pipelines State Object (PSO) encompasses all required states (all shader stages, input layout description, depth stencil, rasterizer and blend state descriptions etc.). This approach maps directly to Direct3D12/Vulkan, but is also beneficial for older APIs as it eliminates pipeline misconfiguration errors. With many individual calls tweaking various GPU pipeline settings it is very easy to forget to set one of the states or assume the stage is already properly configured when in fact it is not. Using pipeline state object helps avoid these problems as all stages are configured at once.
      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 two samples, asteroids performance benchmark and example Unity project that uses Diligent Engine in native plugin.
      AntTweakBar sample is Diligent Engine’s “Hello World” example.

       
      Atmospheric scattering sample is a more advanced example. It 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 and Android platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and support for more platforms is planned.
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