• Advertisement

Advice Leaning how to make a game engine in OpenGL SDL/GLFW

Recommended Posts

A friend of mine and I are making a 2D game engine as a learning experience and to hopefully build upon the experience in the long run.

-What I'm using:

  •     C++;. Since im learning this language while in college and its one of the popular language to make games with why not.
  •     Visual Studios; Im using a windows so yea.
  •     SDL or GLFW; was thinking about SDL since i do some research on it where it is catching my interest but i hear SDL is a huge package compared to GLFW, so i may do GLFW to start with as learning since i may get overwhelmed with SDL.

 

-Questions

  • Knowing what we want in the engine what should our main focus be in terms of learning.
  • File managements, with headers, functions ect. How can i properly manage files with out confusing myself and my friend when sharing code.
  • Alternative to Visual studios: My friend has a mac and cant properly use Vis studios, is there another alternative to it?

 

Share this post


Link to post
Share on other sites
Advertisement

I'm actually making a C framework with OpenGL and GLFW. So, here are my cents.

2 minutes ago, AyeRonTarpas said:

SDL or GLFW; was thinking about SDL since i do some research on it where it is catching my interest but i hear SDL is a huge package compared to GLFW, so i may do GLFW to start with as learning since i may get overwhelmed with SDL.

SDL is a larger library compared with GLFW. It isn't big to the point that will make you "overwhelmed", though. If your game engine will be exclusively 2D, it's a doable option. But, if you want something for 3D, too, then SDL is in my opinion a "waste", since some of its features are dedicated for 2D. It wouldn't impede you from making a 3D engine, but there would be that "waste" of unused features. That said, GLFW is cleaner for doing a single job.

2 minutes ago, AyeRonTarpas said:

Knowing what we want in the engine what should our main focus be in terms of learning.

Is you engine going to manage all assets? Textures, scenes, camera, meshes, animation, shaders/material? You can go with two options, let the engine manage these assets and be responsible for creating and destroying them, or give more power to the user and let the user decide the life time of assets. There's a trade-off here, which is the more power the user have, the more they have to write their own implementations.

How much of OpenGL you two know? If not much, start with "modern" OpenGL (a.k.a. OpenGL with shaders). Don't go with fixed function pipeline (old style OpenGL). OpenGL version 3.3 is a good candidate as I mentioned in other thread: 

Also, how much of OpenGL you will wrap? You certainly will wrap to a degree, since functions to create/delete textures/framebuffers/shaders/VBOs/VAOs will have to use OpenGL.

Quote
  • File managements, with headers, functions ect. How can i properly manage files with out confusing myself and my friend when sharing code.

For each type off asset, have a header (.h/.hpp) and a source (.c/.cpp). Then having a central header (myengine.h/pp) that include the header of the types. If this is a possibility, it helps for who uses your engine to include only a single header.

Use git for version control. There are several workflows to work with git (for example: http://nvie.com/posts/a-successful-git-branching-model/). Some might be too complex for a team of 2 people. Check what works better for you. You will probably make mistakes with your workflow, so just start using it and learn the best approach for you early.

14 minutes ago, AyeRonTarpas said:
  • Alternative to Visual studios: My friend has a mac and cant properly use Vis studios, is there another alternative to it?

He can use clang or gcc with some editor (Atom is a nice one with good integrations). I don't use Visual Studio (Linux), but it seems like it has support for CMake since 2016. Couldn't you use the CMake instead and make the work with the two platforms easier?

Share this post


Link to post
Share on other sites
7 minutes ago, ferreiradaselva said:
7 minutes ago, ferreiradaselva said:

Is you engine going to manage all assets? Textures, scenes, camera, meshes, animation, shaders/material? You can go with two options, let the engine manage these assets and be responsible for creating and destroying them, or give more power to the user and let the user decide the life time of assets. There's a trade-off here, which is the more power the user have, the more they have to write their own implementations.

How much of OpenGL you two know? If not much, start with "modern" OpenGL (a.k.a. OpenGL with shaders). Don't go with fixed function pipeline (old style OpenGL). OpenGL version 3.3 is a good candidate as I mentioned in other thread: 

The engine is going to be more personal between the two we have no plan yet to share the engine unless its within the group ill be working with so i may just have the engine do it entirely.

Both of us are very fresh to OpenGL we know little to nothing, im currently doing research but still know the bare bones i would say. Still learning as i go from video tuts to some discussion. Though some website would be nice if you know some.

 

15 minutes ago, ferreiradaselva said:

He can use clang or gcc with some editor (Atom is a nice one with good integrations). I don't use Visual Studio (Linux), but it seems like it has support for CMake since 2016. Couldn't you use the CMake instead and make the work with the two platforms easier?

I use to exclusively code in Java since highschool so never really explored in any IDEs for C++ i will check out CMake if it makes it easier for us to work on two platforms.

 

Share this post


Link to post
Share on other sites
1 minute ago, AyeRonTarpas said:

Both of us are very fresh to OpenGL we know little to nothing, im currently doing research but still know the bare bones i would say. Still learning as i go from video tuts to some discussion. Though some website would be nice if you know some.

https://learnopengl.com/ is great. And the examples are in C++, since it is what you are going to work with.

Share this post


Link to post
Share on other sites

For a real deep learning purpose, I wrote my own GLFW like wrapper generator that grabbs the khronos specs from github and creates the functions/enums from the xml file that you find there. Otherwise GLFW is a good library to go for, especially for the benefit features of creating window and input handling when the focus isnt going into real cross-platform development (in this case I would also do it on my own because it is very simple to implement that few features you need for each platform using the system APIs, especially when one companion lives on a unix system)

SDL in my opinions is too heavy because it has grown for a full all-in-one solution utilizing OpenGL and DX over the years and it lacks for the learning purpose when not doing certains tuff on your own.

A good point to start is to setup your project first before doing anything else so you initially setup your code reposetory the right way. There are thousands of people doing millions of different reposetory structure so find the one that suits best for you. I have gone with a modular based approach giving each module an own sub-folder and project file so you could work in parallel on different projects that might not influence each other and setup an engine core project anything is put into that any other module is referring to. I have also written an own build tool in C# that helps me setup my project files from a single buildfile (that is some kind of mixed JSON with C++) and is able to trigger the build pipeline (compiler, linker and further steps) from the command line. I'm targeting different OS'es and also console platforms so this seemed to be a good solution for me, you might go with something simple (make for example except that it is too Unix based as it needs a unix shell emulation on Windows). That worked best for me and my engine.

You then have to decide how deep you are planning to go into engine development. One could go for years doing anything on your own with only some help from the OS APIs or a few months using any third party library you could get. It should not be the focus to get buitfull graphics very early rather than a robust and general environment as the main goal of your game engine (this is a quote from someone I couldnt find yet but he's right about that) and dont be frustrated from people telling you to "show" something when doing this. This is the most reasoned part for people quitting because they do not "see" any progress. A game engine consists of much more than graphics that is different management structures for memory, assets, render pipeline and so on, a huge ammount of math (without that you cant render anything) and some utility classes that make life easier.

I personally would also go for at least OpenGL 4 Core profile while I agree to ferreiradaselva that it dosent make any sense any more to learn the good old fixed function pipeline, it dosent make sense either to learn old/outdated GL while most hardware supports it but vendors are now stronger focussing on DX12/Vulkan (and of course VR). There are some major differences for example writing shaders using the obsolete varying qualifier type in GL3.3 vs in / out keywords in GL4+ to at least name one.

To the management point I could recommend the coding guidelines of existing successfull engines like Unreal 4 or Cry as a reference how good code should look like (except the prefix letter from unreal) So that you always choose expressive names to whatever the class/function does and name the file in relation to what is inside. A class providing streamed access to an asset file should be named AssetStream.h or <AssetType>Stream.h while I prefer to store the .cpp files in the same location, there might some project structures use different ones like Include for headers and Source for implementation files. You will loose overview in my opinion especially working on large code bases so I avoid doing this.

A last advice I could provide is to forgett about the straight class oriented model that high languages like Java or C# lead. Use classes when needed but do not wrap classes arround pure static functions while a namespace does the same trick and will provide a little more performance

namespace GL
{
    void Enable(GLenum cap);
}

//instead of

class GL
{
   public:
      static void Enable(GLenum cap);
};

//while access is still the same

GL::Enable(GLDepthTest);

 

Some people might disagree with parts or all of my post but this is my opinion and people out there will have there own one otherwise this questions wouldnt have been asked ;)

Share this post


Link to post
Share on other sites

Hi there,

I think you guys should try to implement by your own every module of a usable engine, this means IO, rendering, sound, input, etc. This way you will learn a lot and will have a good basis of engine development and how videogames work behind the scenes. In the meantime you will face struggles with C++ due to how write the code, dependencies among files, etc. so this will growth your C++ skill too.

I'm not quiet sure you mean in your second question, but I would say you refering how to fix the issue of working together in a same software project, so if I undertood well you both guys should learn some control version like GIT. This allows that several persons work together in same project with no (maybe some haha) issues meanwhile having a consistent track of the development.

Doesn't should a problem find some remplace to Visual Studio-like-editor in MacOS, but the important thing here is use the same compiler, It's not mandatory but for newbies won't add extra hassle in the development.

Also my two cents about SDL vs GLFW: for sure SDL is larger library with tons of functionalities, still doesn't remplace entire modules that in other way you would write by your own and also has a own 2D rendering API so you can put aside OpenGL. GLEW is just a wrapper for OpenGL functions and also offers system events.

I left you here a post I wrote recently about issues you may face at the start of development of a SDL-OpenGL engine.

Edited by vonflaken

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

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

Create an account

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

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Advertisement
  • Advertisement
  • Popular Tags

  • Advertisement
  • Popular Now

  • Similar Content

    • By Ward Correll
      I include the source code from what I am playing with. It's an exercise from Frank Luna's DirectX 12 book about rendering a skull from a text file. I get a stack overflow error and the program quits. I don't know where I went wrong it's messy programming on the parts I added but maybe one of you masterminds can tell me where I went wrong.
      Chapter_7_Drawing_in_Direct3D_Part_II.zip
    • By EddieK
      Hello. I'm trying to make an android game and I have come across a problem. I want to draw different map layers at different Z depths so that some of the tiles are drawn above the player while others are drawn under him. But there's an issue where the pixels with alpha drawn above the player. This is the code i'm using:
      int setup(){ GLES20.glEnable(GLES20.GL_DEPTH_TEST); GLES20.glEnable(GL10.GL_ALPHA_TEST); GLES20.glEnable(GLES20.GL_TEXTURE_2D); } int render(){ GLES20.glClearColor(0, 0, 0, 0); GLES20.glClear(GLES20.GL_ALPHA_BITS); GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT); GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT); GLES20.glBlendFunc(GLES20.GL_ONE, GL10.GL_ONE_MINUS_SRC_ALPHA); // do the binding of textures and drawing vertices } My vertex shader:
      uniform mat4 MVPMatrix; // model-view-projection matrix uniform mat4 projectionMatrix; attribute vec4 position; attribute vec2 textureCoords; attribute vec4 color; attribute vec3 normal; varying vec4 outColor; varying vec2 outTexCoords; varying vec3 outNormal; void main() { outNormal = normal; outTexCoords = textureCoords; outColor = color; gl_Position = MVPMatrix * position; } My fragment shader:
      precision highp float; uniform sampler2D texture; varying vec4 outColor; varying vec2 outTexCoords; varying vec3 outNormal; void main() { vec4 color = texture2D(texture, outTexCoords) * outColor; gl_FragColor = vec4(color.r,color.g,color.b,color.a);//color.a); } I have attached a picture of how it looks. You can see the black squares near the tree. These squares should be transparent as they are in the png image:

      Its strange that in this picture instead of alpha or just black color it displays the grass texture beneath the player and the tree:

      Any ideas on how to fix this?
       
      Thanks in advance
       
       
    • By DiligentDev
      This article uses material originally posted on Diligent Graphics web site.
      Introduction
      Graphics APIs have come a long way from small set of basic commands allowing limited control of configurable stages of early 3D accelerators to very low-level programming interfaces exposing almost every aspect of the underlying graphics hardware. Next-generation APIs, Direct3D12 by Microsoft and Vulkan by Khronos are relatively new and have only started getting widespread adoption and support from hardware vendors, while Direct3D11 and OpenGL are still considered industry standard. New APIs can provide substantial performance and functional improvements, but may not be supported by older hardware. An application targeting wide range of platforms needs to support Direct3D11 and OpenGL. New APIs will not give any advantage when used with old paradigms. It is totally possible to add Direct3D12 support to an existing renderer by implementing Direct3D11 interface through Direct3D12, but this will give zero benefits. Instead, new approaches and rendering architectures that leverage flexibility provided by the next-generation APIs are expected to be developed.
      There are at least four APIs (Direct3D11, Direct3D12, OpenGL/GLES, Vulkan, plus Apple's Metal for iOS and osX platforms) that a cross-platform 3D application may need to support. Writing separate code paths for all APIs is clearly not an option for any real-world application and the need for a cross-platform graphics abstraction layer is evident. The following is the list of requirements that I believe such layer needs to satisfy:
      Lightweight abstractions: the API should be as close to the underlying native APIs as possible to allow an application leverage all available low-level functionality. In many cases this requirement is difficult to achieve because specific features exposed by different APIs may vary considerably. Low performance overhead: the abstraction layer needs to be efficient from performance point of view. If it introduces considerable amount of overhead, there is no point in using it. Convenience: the API needs to be convenient to use. It needs to assist developers in achieving their goals not limiting their control of the graphics hardware. Multithreading: ability to efficiently parallelize work is in the core of Direct3D12 and Vulkan and one of the main selling points of the new APIs. Support for multithreading in a cross-platform layer is a must. Extensibility: no matter how well the API is designed, it still introduces some level of abstraction. In some cases the most efficient way to implement certain functionality is to directly use native API. The abstraction layer needs to provide seamless interoperability with the underlying native APIs to provide a way for the app to add features that may be missing. Diligent Engine is designed to solve these problems. Its main goal is to take advantages of the next-generation APIs such as Direct3D12 and Vulkan, but at the same time provide support for older platforms via Direct3D11, OpenGL and OpenGLES. Diligent Engine exposes common C++ front-end for all supported platforms and provides interoperability with underlying native APIs. It also supports integration with Unity and is designed to be used as graphics subsystem in a standalone game engine, Unity native plugin or any other 3D application. Full source code is available for download at GitHub and is free to use.
      Overview
      Diligent Engine API takes some features from Direct3D11 and Direct3D12 as well as introduces new concepts to hide certain platform-specific details and make the system easy to use. It contains the following main components:
      Render device (IRenderDevice  interface) is responsible for creating all other objects (textures, buffers, shaders, pipeline states, etc.).
      Device context (IDeviceContext interface) is the main interface for recording rendering commands. Similar to Direct3D11, there are immediate context and deferred contexts (which in Direct3D11 implementation map directly to the corresponding context types). Immediate context combines command queue and command list recording functionality. It records commands and submits the command list for execution when it contains sufficient number of commands. Deferred contexts are designed to only record command lists that can be submitted for execution through the immediate context.
      An alternative way to design the API would be to expose command queue and command lists directly. This approach however does not map well to Direct3D11 and OpenGL. Besides, some functionality (such as dynamic descriptor allocation) can be much more efficiently implemented when it is known that a command list is recorded by a certain deferred context from some thread.
      The approach taken in the engine does not limit scalability as the application is expected to create one deferred context per thread, and internally every deferred context records a command list in lock-free fashion. At the same time this approach maps well to older APIs.
      In current implementation, only one immediate context that uses default graphics command queue is created. To support multiple GPUs or multiple command queue types (compute, copy, etc.), it is natural to have one immediate contexts per queue. Cross-context synchronization utilities will be necessary.
      Swap Chain (ISwapChain interface). Swap chain interface represents a chain of back buffers and is responsible for showing the final rendered image on the screen.
      Render device, device contexts and swap chain are created during the engine initialization.
      Resources (ITexture and IBuffer interfaces). There are two types of resources - textures and buffers. There are many different texture types (2D textures, 3D textures, texture array, cubmepas, etc.) that can all be represented by ITexture interface.
      Resources Views (ITextureView and IBufferView interfaces). While textures and buffers are mere data containers, texture views and buffer views describe how the data should be interpreted. For instance, a 2D texture can be used as a render target for rendering commands or as a shader resource.
      Pipeline State (IPipelineState interface). GPU pipeline contains many configurable stages (depth-stencil, rasterizer and blend states, different shader stage, etc.). Direct3D11 uses coarse-grain objects to set all stage parameters at once (for instance, a rasterizer object encompasses all rasterizer attributes), while OpenGL contains myriad functions to fine-grain control every individual attribute of every stage. Both methods do not map very well to modern graphics hardware that combines all states into one monolithic state under the hood. Direct3D12 directly exposes pipeline state object in the API, and Diligent Engine uses the same approach.
      Shader Resource Binding (IShaderResourceBinding interface). Shaders are programs that run on the GPU. Shaders may access various resources (textures and buffers), and setting correspondence between shader variables and actual resources is called resource binding. Resource binding implementation varies considerably between different API. Diligent Engine introduces a new object called shader resource binding that encompasses all resources needed by all shaders in a certain pipeline state.
      API Basics
      Creating Resources
      Device resources are created by the render device. The two main resource types are buffers, which represent linear memory, and textures, which use memory layouts optimized for fast filtering. Graphics APIs usually have a native object that represents linear buffer. Diligent Engine uses IBuffer interface as an abstraction for a native buffer. To create a buffer, one needs to populate BufferDesc structure and call IRenderDevice::CreateBuffer() method as in the following example:
      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 GameDev.net
      This is an extract from Practical Game AI Programming from Packt. Click here to download the book for free!
      When humans play games – like chess, for example – they play differently every time. For a game developer this would be impossible to replicate. So, if writing an almost infinite number of possibilities isn’t a viable solution game developers have needed to think differently. That’s where AI comes in. But while AI might like a very new phenomenon in the wider public consciousness, it’s actually been part of the games industry for decades.
      Enemy AI in the 1970s
      Single-player games with AI enemies started to appear as early as the 1970s. Very quickly, many games were redefining the standards of what constitutes game AI. Some of those examples were released for arcade machines, such as Speed Race from Taito (a racing video game), or Qwak (a duck hunting game using a light gun), and Pursuit (an aircraft fighter) both from Atari. Other notable examples are the text-based games released for the first personal computers, such as Hunt the Wumpus and Star Trek, which also had AI enemies.
      What made those games so enjoyable was precisely that the AI enemies that didn't react like any others before them. This was because they had random elements mixed with the traditional stored patterns, creating games that felt unpredictable to play. However, that was only possible due to the incorporation of microprocessors that expanded the capabilities of a programmer at that time. Space Invaders brought the movement patterns and Galaxian improved and added more variety, making the AI even more complex. Pac-Man later on brought movement patterns to the maze genre – the AI design in Pac-Man was arguably as influential as the game itself.
      After that, Karate Champ introduced the first AI fighting character and Dragon Quest introduced the tactical system for the RPG genre. Over the years, the list of games that has used artificial intelligence to create unique game concepts has expanded. All of that has essentially come from a single question, how can we make a computer capable of beating a human in a game?
      All of the games mentioned used the same method for the AI called finite-state machine (FSM). Here, the programmer inputs all the behaviors that are necessary for the computer to challenge the player. The programmer defined exactly how the computer should behave on different occasions in order to move, avoid, attack, or perform any other behavior to challenge the player, and that method is used even in the latest big budget games.
      From simple to smart and human-like AI
      One of the greatest challenges when it comes to building intelligence into games is adapting the AI movement and behavior in relation to what the player is currently doing, or will do. This can become very complex if the programmer wants to extend the possibilities of the AI decisions.
      It's a huge task for the programmer because it's necessary to determine what the player can do and how the AI will react to each action of the player. That takes a lot of CPU power. To overcome that problem, programmers began to mix possibility maps with probabilities and perform other techniques that let the AI decide for itself how it should react according to the player's actions. These factors are important to be considered while developing an AI that elevates a games’ quality.
      Games continued to evolve and players became even more demanding. To deliver games that met player expectations, programmers had to write more states for each character, creating new in-game and more engaging enemies.
      Metal Gear Solid and the evolution of game AI
      You can start to see now how technological developments are closely connected to the development of new game genres. A great example is Metal Gear Solid; by implementing stealth elements, it moved beyond the traditional shooting genre. Of course, those elements couldn't be fully explored as Hideo Kojima probably intended because of the hardware limitations at the time. However, jumping forward from the third to the fifth generation of consoles, Konami and Hideo Kojima presented the same title, only with much greater complexity. Once the necessary computing power was there, the stage was set for Metal Gear Solid to redefine modern gaming.
      Visual and audio awareness
      One of the most important but often underrated elements in the development of Metal Gear Solid was the use of visual and audio awareness for the enemy AI. It was ultimately this feature that established the genre we know today as a stealth game. Yes, the game uses Path Finding and a FSM, features already established in the industry, but to create something new the developers took advantage of some of the most cutting-edge technological innovations. Of course the influence of these features today expands into a range of genres from sports to racing.
      After that huge step for game design, developers still faced other problems. Or, more specifically, these new possibilities brought even more problems. The AI still didn't react as a real person, and many other elements were required, to make the game feel more realistic.
      Sports games
      This is particularly true when we talk about sports games. After all, interaction with the player is not the only thing that we need to care about; most sports involve multiple players, all of whom need to be ‘realistic’ for a sports game to work well.
      With this problem in mind, developers started to improve the individual behaviors of each character, not only for the AI that was playing against the player but also for the AI that was playing alongside them. Once again, Finite State Machines made up a crucial part of Artificial Intelligence, but the decisive element that helped to cultivate greater realism in the sports genre was anticipation and awareness. The computer needed to calculate, for example, what the player was doing, where the ball was going, all while making the ‘team’ work together with some semblance of tactical alignment. By combining the new features used in the stealth games with a vast number of characters on the same screen, it was possible to develop a significant level of realism in sports games. This is a good example of how the same technologies allow for development across very different types of games.
      How AI enables a more immersive gaming experience
      A final useful example of how game realism depends on great AI is F.E.A.R., developed by Monolith Productions. What made this game so special in terms of Artificial Intelligence was the dialog between enemy characters. While this wasn’t strictly a technological improvement, it was something that helped to showcase all of the development work that was built into the characters' AI. This is crucial because if the AI doesn't say it, it didn't happen.
      Ultimately, this is about taking a further step towards enhanced realism. In the case of F.E.A.R., the dialog transforms how you would see in-game characters. When the AI detects the player for the first time, it shouts that it found the player; when the AI loses sight of the player, it expresses just that. When a group of (AI generated) characters are trying to ambush the player, they talk about it. The game, then, almost seems to be plotting against the person playing it. This is essential because it brings a whole new dimension to gaming. Ultimately, it opens up possibilities for much richer storytelling and complex gameplay, which all of us – as gamers – have come to expect today.
       
    • By mister345
      Hi guys, so I have about 200 files isolated in their own folder [physics code] in my Visual Studio project that I never touch. They might as well be a separate library, I just keep em as source files in case I need to look at them or step through them, but I will never actually edit them, so there's no need to ever build them.
      However, when I need to rebuild the entire solution because I changed the other files, all of these 200 files get rebuilt too and it takes a really long time.
      If I click on their properties -> exclude from build, then rebuild, it's no good because then all the previous built objects get deleted automatically, so the build will fail.
      So how do I make the built versions of the 200+ files in the physics directory stay where they are so I never have to rebuild them, but
      do a normal rebuild for everything else? Any easy answers to this? The simpler the better, as I am a noob at Visual Studio settings. Thanks.
  • Advertisement