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OpenGL OpenGL Vs Monogame

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So after much thought and a few posts on this site, as well as watching the MicrosoftVirtualAcademy course where they show you Construct 2, Gamemaker and Unity, I decided the best thing for me at this moment is to take a step back and just use a framework to start learning some game development so I can get as much C# experience as I can as I really enjoy the hands on experience.

 

Now, upon further research, it appears that OpenGL and Monogame are similar, and I think I read that Monogame actually uses OpenGL? Is there a benefit to one or the other?

 

I have acquired two books on this subject, one uses OpenGL called C# Game Programming for Serious Game Design and the other uses Monogame, called Learn 2D Game Development with C#. Which should I start out in as a beginner game developer, OpenGL or Monogame and is there a better resource out there? It appears both books cover things like game math and physics pretty well, but the one using OpenGL may be a little more detailed, I've just browsed both books and haven't looked into it fully. 

 

Thanks for any help!

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They are different APIs/Frameworks. Monogame is based on Mono, the crossplattform version of the .NET framework. It might contain some 2d graphics capability, but to utilize 3d graphics capability you would need one of the 3d graphics APIs. Microsofts perferred way would be DirectX for .NET, but with Mono being crossplattform, OpenGL is the way to go for 3d graphics (DirectX is not crossplattform).

 

So, you might use Monogame to start coding your game, and it might be sufficient for 2d games, but once you want 3d, it seems you need OpenGL too.

Edited by Ashaman73

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OpenGL is an API for sending commands to the GPU.

MonoGame is basically a simplistic game engine -- a collection of APIs that deal with graphics, audio, asset loading, user input, etc...
Inside MonoGame's graphics components, it will use OpenGL to send commands to the GPU in order to draw things.
(n.b. Different platforms have different APIs for controlling the GPU, so actually, it will use OpenGL, OpenGL|ES, D3D11 via SharpDX or GNM depending on which platform you're using it on!)

OpenGL deals with low-level commands, like sending texture data to GPU memory, binding shaders, drawing triangles and projecting vertices.
MonoGame deals with high-level commands, like load this 3D model from disc, draw this 3D model to the screen.

If you want to learn how to control a GPU, then use OpenGL.
If you want to learn how to make games, use MonoGame.

DirectX is not crossplattform

Just to be pedantic tongue.png
D3D runs on: 3 game consoles (5 on DC, 9 on Xb360, 11 on XbOne), Windows Phones, and PCs (via Windows/Linux+Wine).
OpenGL runs on: only PCs (via Windows/Mac/Linux) and it's sister GL|ES runs on Android/iOS.
There's also emulation layers to run GL|ES on PC via D3D, and to run D3D on Mac/Linux/PS4 via GL/GNM.
So it depends on how you define cross-platform - depending on your target platforms, either could be more cross-platform than the other laugh.png
Mobile/PC devs will get most reuse by writing a shared GL & GL|ES engine (with ifdef's around the differences) and porting to consoles as a 2ndary concern.
Console/PC devs will get most reuse by writing a shared D3D engine (and porting to Sony) and porting to Mac/Linux/mobile as a 2ndary concern. Edited by Hodgman

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So, you might use Monogame to start coding your game, and it might be sufficient for 2d games, but once you want 3d, it seems you need OpenGL too.

 

Monogame is a full implementation of XNA on Mono, and as such includes all the 3d graphics APIs that are in XNA. These are wrappers over OpenGL or DirectX (depending on the platform).

Edited by phil_t

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D3D runs on: 3 game consoles, Windows Phones, and PCs (via Windows/Linux+Wine).

OpenGL runs on: only PCs (via Windows/Mac/Linux).

 

Oh! I never realized that!

This "OpenGL ES" thingy that I see on 90+% of all mobile phones and tablets is actually based on D3D and not OpenGL, then? ;-)

 

*SCNR*

Edited by sgt_barnes

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No. OpenGL ES runs 'natively' on mobiles. A very common way to emulate OpenGL ES on desktop systems is to use ANGLE (which offers an OpenGL ES interface but renders internally using DirectX). The advantage is that you need less platform-specific code if you work on both desktop. Additionally some OpenGL drivers on desktop are horribly bad (especially when you move towards older cards on extremely casual gamer systems) and using ANGLE can work around that problem.

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(sgt_barnes was joking)

 

The response was valid though....

 

A lot of folks say "cross-platform" when what they really mean is "Unix, Unix and more Unix".

 

One also needs to consider software platforms vs hardware platforms.

 

We can accept that OpenGL has better compatibility across software platforms (bearing in mind the caveats in Hodgman's post above).

But we must also accept that D3D has better compatibility across hardware platforms.

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Monogame is based on Mono, the crossplattform version of the .NET framework. It might contain some 2d graphics capability, but to utilize 3d graphics capability you would need one of the 3d graphics APIs. Microsofts perferred way would be DirectX for .NET, but with Mono being crossplattform, OpenGL is the way to go for 3d graphics

 

So if I want to make a 2D game, should I stick with Mono? Or can OpenGL be used for 2D graphics as well as 3D graphics?

 


MonoGame is basically a simplistic game engine -- a collection of APIs that deal with graphics, audio, asset loading, user input, etc...

 

I'm not sure I want to use even a simplistic game engine. I thought the game engine was the way for me to go, but after really looking into it I found them to be too much point and click and not enough actual coding. I really want to have full access to program user input, save states, collisions, etc on my own. While I know C# syntax I'm still trying to get use to all the useful classes and combining syntax to do certain things. I want as much hands on as possible when I make my games to give myself as much practice as possible, then in the future I can always move over to an engine of choice. 

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So if I want to make a 2D game, should I stick with Mono? Or can OpenGL be used for 2D graphics as well as 3D graphics?


OpenGL can do both 2D and 3D. I'm using OpenGL now and only focus on 2D
 

I'm not sure I want to use even a simplistic game engine. I thought the game engine was the way for me to go, but after really looking into it I found them to be too much point and click and not enough actual coding. I really want to have full access to program user input, save states, collisions, etc on my own. While I know C# syntax I'm still trying to get use to all the useful classes and combining syntax to do certain things. I want as much hands on as possible when I make my games to give myself as much practice as possible, then in the future I can always move over to an engine of choice.


Now this is based on my experiences

Originally when I started coding my games using "only code" I started with Microsoft's XNA which uses C#. And for me that was awesome! I wanted to do 2D games and it had everything I needed. Then when I heard Microsoft dropped XNA, I made the big leap to doing everything by myself from scratch. I ended up switching languages to C++ and moving to DirectX9, then to DirectX11, then to OpenGL for cross-platform support, then to OpenGL ES cause my friend was more comfortable do mobile stuff. And now I'm back at using OpenGL. So I have been across the spectrum of APIs and back. I have to admit doing things from scratch has definitely grown on me

 

I have noticed they all have one thing in common though. No matter what API (OpenGL or DirectX) you choose, when making things from scratch vs using a pre-made game engine/framework there is a huge learning curve. Don't get me wrong, I feel like I have become a better programmer and to me personally it has been rewarding. And I like the feeling that I get, that feeling of complete control. But you need to ask yourself the golden question:

 

Do you have the time and patience to make all the features you need and then all the features you want. When you know that those features are more than likely readily available in another game engine/framework? Plus the time and patience it takes to build and design your game on top of that?

 

Building a game in itself is a difficult task, which requires a starting point. And building this point from scratch is also a difficult task

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Don't get me wrong, I feel like I have become a better programmer and to me personally it has been rewarding. And I like the feeling that I get, that feeling of complete control. But you need to ask yourself the golden question:
 
Do you have the time and patience to make all the features you need and then all the features you want. When you know that those features are more than likely readily available in another game engine/framework? Plus the time and patience it takes to build and design your game on top of that?

 

This is exactly why I am writing a game from scratch. I want to become a better programmer, and using something like OpenGl or Monogame, where some of the behind-the-scenes work is done for me but ultimately I have control, will help me overall become better. I'm writing a game for fun, but also to have a fun project to help increase my skill at programming. In the future, once I am comfortable in programming to where I don't need as much practice, I can try out an engine, but for now I feel I need to get my hands dirty and just code. :)

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MonoGame is still rather low level. It's not a game engine, it just contains a lot more high-level stuff that is useful in game development. MonoGame can be used for 3D with an API that is very similar to Direct3D9. You still draw your own triangles and write your own shaders.

 

You can also use MonoGame for 2D stuff, but it's definitely not 2D only.

 

MonoGame will get you started faster, will be easier to port and work with and will most likely leave you in control over the things you actually care about. OpenGL is graphics only, MonoGame is graphics, sound, resource loading, math, networking and more. There's also alot more support and resources for using MonoGame than using OpenGL _with C#_ in my experience.

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Every game is powered by a "game engine".
Drag'n'drop game-maker GUIs with visual scripting are not the only form of game engine.

If you choose to make a game without one, then you'll have built one by the time you're done.
The parts of your code that power the game, but aren't specific to the gameplay are "the engine".
Even if you make something simple like "pong" from scratch, you'll have built a "pong engine", which you can utilise to make other "pong-style" games, such as breakout.

I thought the game engine was the way for me to go, but after really looking into it I found them to be too much point and click and not enough actual coding. I really want to have full access to program user input, save states, collisions, etc on my own. While I know C# syntax I'm still trying to get use to all the useful classes and combining syntax to do certain things. I want as much hands on as possible when I make my games to give myself as much practice as possible, then in the future I can always move over to an engine of choice.

The first part isn't true - you'll still have to do a tonne of programming when using an existig engine.
If you don't use something like MonoGame, you'll just have to create your own version of it first, AND then build the game on top of your own "NotMonoGame" in exactly the same way that you would have done anyway.

As for the second part, if you're the kind of person who learns by doing, you'll probably be better off building your first games within existing, well designed, proven frameworks. Not only will you actually see results faster, but in the process of using these existing frameworks you'll be reading/using code written by expert game programmers, and gain a good understanding of how these base systems are often structured. Then later, when you try to build a game from scratch (AKA, buildnyour own engine) you'll already be a somewhat experienced game programmer, so you'll know what your engine should look like.

IMHO, trying to build an engine before you've built games is like trying to build a race-car before you've got a drivers license... Actually: before you've even ever driven in a car at all!
Sure it can be done, but an engineer/craftsman will do better to understand the users of their craft.

Even if your goal was to become a game-engine programmer, rather than a game programmer, I'd still advocate learning to make games on many different existing game engines first, so you understand the needs of your users (i.e. Game programmers) before trying to build your own engine.


Also don't underestimate the amount of work involved in either option.
When I worked in the games industry on low-budget games:
* when we used an existig engine, we had 2 engine programmers dedicated to modifying/maintaining that engine, plus a dozen gameplay programmers.
* when we used our own engine, we had two dozen engine/tools programmers and a dozen gameplay programmers.
For a simple 8-month game project, that's somewhere around 10 to 30 man-years of work, just on programming! Also, all of those staff had 5+ years of tertiary education/experience to begin with...

Completing any game as a 1-man band is a huge achievement to look forward to.

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Or can OpenGL be used for 2D graphics as well as 3D graphics?

 

2D is just a special case of 3D.

 

With 3D, each point has a third co-ordinate (representing depth) (I'm simplifying a bit here) whereas with 2D that third co-ordinate is the same for all points.  So anything that can do 3D can also do 2D, no problem at all.

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      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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