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DX12 I want to begin the journey in the best way

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I want to start working on a project (as a student), but I want to start as best as I can.

I want to make something in 3D. Cool! (I thought and still). So I started making a character in Blender and exported for Threejs... the exported didn't work (may probably be my fault tho); same for Babylonjs. Same with 3ds Max: sometimes it works on a browser but not on another.

I guess I'll just go with DirectX. But it's going to take so much time (that's not a problem... I have a few months)! Plus: if my files are big, my browser will start crying... so maybe a desktop application could be better?

Instead of going there, try it, doesn't work, change, try, doesn't work, (while !done {work}), I decided to ask for your help.

I don't know how components can be put together: I can make a .blend file (/max), but how do I show that? How do I put it in my codes? Now tell us what you think you can do!

OK:

  • I create my character and environment with Blender/Max
  • Animations in Blender/Max
  • Export
  • Win32 simple window
  • DirectX calls to show characters, environments; add events and so on

I have seen a book's source codes and it has models in the .m3d format and .txt format. As I think I will follow that book, I hope there won't be problems in exporting or converting to those extensions. (it's nice to see the text files).

I won't use engines such as Unity or Unreal, because for the project I have to mainly code; I'm modelling something because I prefer to make them on my own.

I would follow "Introduction to 3D Game Programming with DirectX 12" (coming out in a month)

Something I would like to make is this; but I haven't decided yet

Edited by keruyo

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Hi Keruyo

 

When you say you won't use engines such as Unity or Unreal, is it because you would prefer to learn to code with a language rather than using a game engine?

If you want to make a 3D game, they will certainly do much of the heavy lifting for you.

 

I think most people will recommend you start small and build from there.

 

So far, I have coded Hangman, Deal or No Deal, a remake of a Commodore64 Graphic Adventure game and now I'm making a Zombie racing game. None of these even involve physics yet :)

 

I'm making all of these in JavaScript mainly because they run in a standard web browser.

 

I would encourage you to make smaller goals to begin with and go forward from there.

 

Good luck.

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Hi Keruyo

 

When you say you won't use engines such as Unity or Unreal, is it because you would prefer to learn to code with a language rather than using a game engine?

If you want to make a 3D game, they will certainly do much of the heavy lifting for you.

 

I think most people will recommend you start small and build from there.

 

So far, I have coded Hangman, Deal or No Deal, a remake of a Commodore64 Graphic Adventure game and now I'm making a Zombie racing game. None of these even involve physics yet smile.png

 

I'm making all of these in JavaScript mainly because they run in a standard web browser.

 

I would encourage you to make smaller goals to begin with and go forward from there.

 

Good luck.

Hi Geejayz

About engines: my project is about coding; I am allowed to use them, but warned that if it's just going to be a bunch of scripts, it just won't happen. So I'd prefer to write something on my own, even though it won't be like Assassin's Creed, but to code :--)

I would follow the book I mentioned in my first post to do something like the image I linked, maybe. If I change my mind, I think I will have enough experience by that point to do some code on my own (still not anything impossible)

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This is a project as in something you will earn credits/get assessed on? What is the purpose of this project, is it to make a model viewer? Are you wanting to make a full on game etc? Would making a program that just loads a model and plays some animations be enough? Even that is a lot of work when you have animations and various materials.

 

If you want to make a game and also use your own models that you have made then I would recommends you use a more specific engine, something like Orge3D would let you use your own models, complete with animations, materials and so on. It is entirely a graphics engine and not to be mistaken with things like Unity/Unreal/CryEngine which offer almost all aspects of a game. In that respect it leaves you with a great deal of coding to do, it wouldn't be writing scripts or smaller sections of code like you would with some of the full game engines.

 

Decide what it is exactly you want to achieve, what is the main focus of your project (is it modelling, is it coding), how long do you have etc and that will help people give you better advice.

 

Full on game engines might not leave you with much to do but more specific engines (more libraries/frameworks really) will help you out a great deal and still leave you with a lot that you have to do yourself. They will free you up to do something more interesting.

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To add what has been said before: You are currently in danger of biting off more than you can chew.

 

That is fine for your own personal hobby projects that have no deadline you need to follow. Its not a good idea for a project with a deadline, even less if your school marks could depend on it.

 

A) Make sure you understand EXACTLY what your school wants you to do and what you are measured on. If you are just measured on your code, make sure you don't waste time modelling. Yes, modelling is fun, and being able to create a model and understand the full pipeline can be benefical even for a programmer. But you are not doing your current project for fun.

B) Concentrate on the aspects that you are rated on. Does your school mainly look on the quality of code written? Make a small game, but polish the code until it sparkles. Do they want to see you apply patterns and algorithms to "real world problems"? Make sure you tick all the boxes, even if the pattern sometimes only fits with some imagination.

 

 

3D Modelling is a huge topic in itself. Its cool and fun, but its A LOT to learn to successfully create and export 3D models and be able to use them in a working 3D application. You certainly can quickly kitbash something out of boxes and spheres and get it to run, but even then, given that you don't follow the pre existing engine route, there is a lot involved with 3D games and importing / using 3D models in them.

 

 

If you are dead sure you need to go 3D (A 2D graphics game is MUCH easier to create if you go the low level route without an engine), and you want to stick to not using a pre existing engine (its not like Unity or Unreal does the coding for you, there is so much more to code besides the low level stuff, but I could see that low level programming might be an easier sell for your teachers)...

Look for pre-existing free 3D models online and use them. Look for tutorials on importing and using 3D Models for whatever low level route you take. Preferably, you don't try to re-invent the wheel (Because then even months might not be enough at your current stage), and start with something like SDL or Mono as a Framework to build on.

 

 

About 3D Formats:

.obj and .fbx are the common "portable" formats used by most engines and frameworks I know. Each 3D Tool has its own format (like .blender for the Blender 3D Package), but these usually do not import well into other 3D tools. Unity has a .blender importer, but even then I would rather export the model as .obj or .fbx from Blender so that I could use Unitys importers for the more common file formats. I wouldn't even dare to try to import some of the more obscure file formats of the smaller 3D programs as there is all kind of things that can go wrong during import.

 

the two file formats you mention seem to be rather obscure... haven't even heard of Corel Motion before. What tool are you using for creating your models?

Edited by Gian-Reto

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What is the purpose of this project, is it to make a model viewer?

The purpose is, basically, anything. I can do anything that relates to graphics, but it must be mainly coding (because that's what I'm studying..): games (obvious idea), games' tools, it happened a guy made graphics API; anything "visual" or related

 


Would making a program that just loads a model and plays some animations be enough?

It would be I think; like Blade&Soul when you choose your character, right?

 

 


...something like Orge3D... In that respect it leaves you with a great deal of coding to do

I thought about it, though I didn't find too many books about it and as I'm not really experienced I thought to follow books. I will check for their documentation

 

 


Decide what it is exactly you want to achieve, what is the main focus of your project (is it modelling, is it coding), how long do you have etc and that will help people give you better advice.

The main project is coding. It could be days or months; of course, I'm not in a rush, but I don't want it to last for more than half a year or so (as I will be doing other stuff in the meantime)

 

 


That is fine for your own personal hobby projects that have no deadline you need to follow. Its not a good idea for a project with a deadline, even less if your school marks could depend on it.

I have no "real" deadline, but as I said above, it shouldn't take too many months. Your sentence helped ;p

 

 


A) Make sure you understand EXACTLY what your school wants you to do and what you are measured on. If you are just measured on your code, make sure you don't waste time modelling. Yes, modelling is fun, and being able to create a model and understand the full pipeline can be benefical even for a programmer. But you are not doing your current project for fun.

I didn't say anything about it, but it is actually so fun :-) But you're right, it may waste take too much time.

 

 


B) Concentrate on the aspects that you are rated on. Does your school mainly look on the quality of code written? Make a small game, but polish the code until it sparkles. Do they want to see you apply patterns and algorithms to "real world problems"? Make sure you tick all the boxes, even if the pattern sometimes only fits with some imagination.

I have no information about this. It's about coding; then I will choose what to do with the language(s) I choose to code with

 

 


You certainly can quickly kitbash something out of boxes and spheres and get it to run, but even then, given that you don't follow the pre existing engine route, there is a lot involved with 3D games and importing / using 3D models in them.

Exactly. I was following a tutorial and anything that wasn't there, was really tough

 

 


If you are dead sure you need to go 3D (A 2D graphics game is MUCH easier to create if you go the low level route without an engine), and you want to stick to not using a pre existing engine (its not like Unity or Unreal does the coding for you, there is so much more to code besides the low level stuff, but I could see that low level programming might be an easier sell for your teachers)...

I don't need to go 3D; I just thought it could be cooler without any cool ideas. I mean, 2D chess is 0% tongue.png Something 'old' like a walking character with a GUI, a character selection screen, are old but still better than Snake (not for the game itself, but because it's nothing new and cool).

Ogre3D could work out. As above, I can use Unity, but then what's left to me? Low level programming may get tons of trouble and waste of time, you're right.

I even thought about C#, but I see only XNA / Unity books that use it.

 


start with something like SDL or Mono as a Framework to build on

I didn't know SDL; I'm looking into it right now

 

 


the two file formats you mention seem to be rather obscure... haven't even heard of Corel Motion before. What tool are you using for creating your models?

I saw them in the source codes of "Introduction to 3D Game Programming with DirectX 11" (downloaded from his website).

Edited by keruyo

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I don't need to go 3D; I just thought it could be cooler without any cool ideas. I mean, 2D chess is 0% tongue.png Something 'old' like a walking character with a GUI, a character selection screen, are old but still better than Snake (not for the game itself, but because it's nothing new and cool).

 

I know what you mean, but make sure your excitment for something "fun" does not let you loose sight of your goal. Which is to finish your work, and get good marks.

 

Now, programming the game logic for 2D or 3D games is not that different. 2D games today tend to be much simpler than most 3D ones, but that is more because 2D graphics are mostly chosen for the sake of simplicity and fitting into a tight budget.

 

Graphics programming between 3D and 2D differs a lot of course, though many 2D games nowadays are built on a "3D foundation"... like 2D games built with the Unity engine.

 

Generally, your choice of graphics will not affect your coding too much. You could build a 3D game with simple boxes and spheres as characters, and a level built of simple grey boxes, and code a complex physics simulation and AI agents to go with it. You could do almost the same with even simpler 2D graphics.

 

 

 

 


Ogre3D could work out. As above, I can use Unity, but then what's left to me? Low level programming may get tons of trouble and waste of time, you're right.

I even thought about C#, but I see only XNA / Unity books that use it.

 

I think you make the usual newbie mistake in overestimating what a game engine does.

 

What a game engine usually does is free you from the hassle of doing low level plumbing to get DirectX or OpenGL to do your bidding. It will also deliver some helpers like pre written shaders and stuff like that, as well as tools to ease the content creation / importing and a ton of tutorials and samples.

 

What an engine does not is allow you to click your game together in the editor and just hit play... what happens then is you have a static view of your assembled level without any interactivity. If you want interactivity, you need to write code. There are many options nowadays (third party assets, visual scripting tools, and so on) that ease that task further. Generally speaking though, the game logic, AI code and Physics engine glue code still is left for you to write. You can copy it from some example, but you don't have to.

You can dive deeper, write your own shaders if you want to, or even alter the engines low level code in some cases.

 

You might not NEED to do as much coding as when going the DIY route. But you CAN do almost as much coding, if you have the time and need for it.

 

Unity and Unreal Engine 4 are the usual choices for Indie / Hobbysts interested in 3D development. Both do have a learning curve, steep with Unity and even steeper with Unreal. But that is true of every 3D engine. The upside is both engine are "free" (totally free in your case), come with lots and lots of tutorials and a large community to rely on.

 

Languages of choices are C++ for Unreal and C# for Unity. I can tell you that the C# API for Unity is fantastic, had a very easy time getting into it as a longtime Java dev... I am currently struggling a bit with Unreals C++, but that has more to do with me not having had enough time to really sit down and dig into it than it being really that hard to learn.

 

 

 

 


I saw them in the source codes of "Introduction to 3D Game Programming with DirectX 11" (downloaded from his website).

 

Make sure that if you continue to use this book as a reference, you understand that the file formats they use are not really the generally accepted standart. There is a good possibility that at least some of your model import problems would be gone if you use .obj or .fbx file formats, and common tools like Blender to create and transfer your 3D models

 

 

 

 

As a possible route for you to go, find an idea that interests you, lay out what makes it special / where it needs special code, research it thouroughly to make sure you don't overcommit and understand possible solutions, then you try to find a way to solve the problem in the most efficient way that still leaves enough room for you to show your coding skills.

 

If your plans are modest, stay DIY... use something like SDL or Mono, maybe even try to implement directly with DirectX or OpenGL. Just make sure you now cut back the game logic / physics interaction / AI to a minimum so you have enough time to create and test your low level stuff and shader code.

 

If you want to achieve a little bit more in the time that you have left, look into an engine. PLAN IN SOME TIME TO LEARN TO USE THE ENGINE! Its not a plug and play affair. If you are able to get up and running in a short enough time, you might leave the low level stuff to the engine and now concentrate on more elaborate game logic or AI code.

Like implementing your own A* path search. A complex shooting and hit locations system, or whatever you want to do.

 

 

Make sure you have a CLEAR chunk of the project layed out for you to implement, that sounds about right in complexity both for satisfying your schools rules, and for you to implement in the time left. And then concentrate on that, and make sure you don't get distracted by other coding, 3D modelling or whatnot above the absolute minimum required.

 

 

You can always make something cooler, more exciting later on in your free time. Better to take risks then, when nothing else than your time left for other hobbies is at stake.

Edited by Gian-Reto

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I know what you mean, but make sure your excitment for something "fun" does not let you loose sight of your goal. Which is to finish your work, and get good marks.

...

You can always make something cooler, more exciting later on in your free time. Better to take risks then, when nothing else than your time left for other hobbies is at stake.

You're right, I'll try to set small goals. My teacher (who doesn't, but especially) loves cool stuff, and something really cool could shoot my mark up in the sky :)


I think you make the usual newbie mistake in overestimating what a game engine does. [...] If you want interactivity, you need to write code.

... the game logic, AI code and Physics engine glue code still is left for you to write. You can copy it from some example, but you don't have to.

You can dive deeper

Getting to better results for our eyes without spending years. I made that mistake :-) Now I understand it couldn't be that bad idea


As a possible route for you to go, find an idea that interests you, lay out what makes it special / where it needs special code, research it thouroughly to make sure you don't overcommit and understand possible solutions, then you try to find a way to solve the problem in the most efficient way that still leaves enough room for you to show your coding skills.Make sure you have a CLEAR chunk of the project layed out for you to implement, that sounds about right in complexity [...] And then concentrate on that, and make sure you don't get distracted

You can always make something cooler, more exciting later on in your free time. Better to take risks then, when nothing else than your time left for other hobbies is at stake.

That's the main problem. Finding that idea is my main issue right now. I will try to think about something; I've seen too many AAA games and thinking about something smaller doesn't satisfy me, but it needs to :P

(looking into SDL right now!)

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      BufferDesc BuffDesc; BufferDesc.Name = "Uniform buffer"; BuffDesc.BindFlags = BIND_UNIFORM_BUFFER; BuffDesc.Usage = USAGE_DYNAMIC; BuffDesc.uiSizeInBytes = sizeof(ShaderConstants); BuffDesc.CPUAccessFlags = CPU_ACCESS_WRITE; m_pDevice->CreateBuffer( BuffDesc, BufferData(), &m_pConstantBuffer ); While there is usually just one buffer object, different APIs use very different approaches to represent textures. For instance, in Direct3D11, there are ID3D11Texture1D, ID3D11Texture2D, and ID3D11Texture3D objects. In OpenGL, there is individual object for every texture dimension (1D, 2D, 3D, Cube), which may be a texture array, which may also be multisampled (i.e. GL_TEXTURE_2D_MULTISAMPLE_ARRAY). As a result there are nine different GL texture types that Diligent Engine may create under the hood. In Direct3D12, there is only one resource interface. Diligent Engine hides all these details in ITexture interface. There is only one  IRenderDevice::CreateTexture() method that is capable of creating all texture types. Dimension, format, array size and all other parameters are specified by the members of the TextureDesc structure:
      TextureDesc TexDesc; TexDesc.Name = "My texture 2D"; TexDesc.Type = TEXTURE_TYPE_2D; TexDesc.Width = 1024; TexDesc.Height = 1024; TexDesc.Format = TEX_FORMAT_RGBA8_UNORM; TexDesc.Usage = USAGE_DEFAULT; TexDesc.BindFlags = BIND_SHADER_RESOURCE | BIND_RENDER_TARGET | BIND_UNORDERED_ACCESS; TexDesc.Name = "Sample 2D Texture"; m_pRenderDevice->CreateTexture( TexDesc, TextureData(), &m_pTestTex ); If native API supports multithreaded resource creation, textures and buffers can be created by multiple threads simultaneously.
      Interoperability with native API provides access to the native buffer/texture objects and also allows creating Diligent Engine objects from native handles. It allows applications seamlessly integrate native API-specific code with Diligent Engine.
      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.
    • By turanszkij
      I am doing a DX12 graphics wrapper, and I would like to update constant buffers. I found the ID3D12GraphicsCommandList2::WriteBufferImmediate method, which is apparently available from a Windows 10 Creators update only. I couldn't really find any info about this (and couldn't try it yet), am I correct to assume this would be useful for writing to constant buffers without much need to do synchronization? It seems to me like this method copies data to the command list itself and then that data will be copied into the DEFAULT resource address which I provided? The only synchronization needed here would be transition barriers to COPY_DEST before WriteBufferImmediate() and back to GENERIC_READ afterwards? I could be totally off though, I'm still wrapping my head around a lot of things.
      What other use cases would this method allow for?
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