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OpenGL Inspired By The Demoscene: Beginner Starting His Journey In Graphics Programming.. Seeking Advice

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Hi everyone!

 

So ever since I watched a few youtube videos of demos created by people from the demoscene, I have been fascinated by Graphics Programming. The way it allows us to express our creativity, artistic vision, and at the same time, showcase our programming prowess is something that have made a big impression on me.

 

 However, knowing how ardous this road is, I was hoping if anyone who have taken the plunge into Graphics Programming could share some advice, or point me in the right direction ?

 

I have some programming experience (namely Python) though I wouldn't call myself a very 'experienced' programmer. In addition, I have done majority of the college level math classes in the past: calculus, linear algebra, discrete mathematics- though I'll have to admit, that's largely forgotten by now ^_^

 

From my understanding, I would need to:

 

1. Learn C++:

I will be picking up a book or two on the subject soon, but if anyone have any good suggestions of a book on C++ that they think would be perfect for a beginner please let me know!

 

I know that C++ is one of the more complex languages when it comes to programming and that one never stops learning when it comes to C++ because of the plethora of libraries it has, but for Graphics Programming, what are some of the key programming concepts or area of focus I should pay more attention to while learning C++? And just how much fluency I would need to acquire before I should even attempt to learn about Graphics Programming? (once I have the fundamentals down? once I have reached an intermediate level?)

 

2. Brush up on Linear Algebra and more specifically, have a solid understanding of the use and applications of Vectors and Matrices?    (these seems to be the most important mathematical concepts when it comes to Graphics Programming right? as they are related to transformation and animation.

Are there anything else beside these two? Quaternions? Trigonometry?

   

3. Choose between DirectX or OpenGL

Personally I would probably pick OpenGL as it's crossplatform, so what comes next is understanding the entire openGL pipeline, its libraries, etc? glsl, shaders?

 

 

With so many things yet to learned, and how much depth Graphics Programming actually covers, it truly feels a little daunting.

If you were to advice a novice on how he should get started, what would be the step by step approach you would suggest? What would you recommend him to learn first, second, third.. etc. What learning materials would you recommend?

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Welcome to the wonderful world of graphics programming! I'll try to answer some of those questions for you.

 

1. Learn C++:

Any language which has access to a well-documented graphics library will do, so you don't necessarily have to go for C++. Honestly, if this is your first experience with programming I'd actually recommend going for something like C#. There's plenty of awesome libraries or wrappers available to do graphics related programming and it'll allow you to get up and running more quickly. It's going to be a while before you can get any real benefit out of working in C++ anyway, so it might be a smaller hurdle to get over by sticking with a more "approachable" language. I know a lot of people have different opinions on this though, so I'll let others add their opinions to this as well.

 

2. Brush up on Linear Algebra and more specifically, have a solid understanding of the use and applications of Vectors and Matrices?

Absolutely! Understanding linear algebra and trigonometry is going to help you out a lot if you want to make any progress. Once you advance a bit further it can become useful to have a good grasp of some elementary concepts in calculus, like differentials and integrals. Once you're at the point where you need those you should have an understanding of the following mathematical concepts you're going to need to advance. It's best not to worry about very complex things for now, just basic linear algebra can already get you far.

 

3. Choose between DirectX or OpenGL Personally I would probably pick OpenGL as it's crossplatform, so what comes next is understanding the entire openGL pipeline, its libraries, etc? glsl, shaders?

The fact that the OpenGL standard is supported on multiple platforms does not mean that it will work out of the box across multiple platforms or even across multiple graphics hardware vendors. OpenGL is notorious for being very inconsistent in these cases. If you're starting out I wouldn't focus on getting things to work on multiple platforms just yet. Start off with one and see how far you get. Worry about the mess that is cross-platform graphics development later.

 

If you want to focus on actually implementing graphical techniques (i.e. you actually want to write code and shaders to get thing to show up on screen asap) I'd actually recommend going with something a little higher level than plain DirectX or OpenGL. I'm a bit out of the loop on publicly available graphics engines, but there's plenty of them out there. I know libraries like Ogre used to be very popular, but I haven't had a look at any of those libraries in years. Even working in Unreal and Unity for experimenting with shaders and such can be a great introduction without too much stuff getting in your way.

I'd recommend looking at OpenGL and DirectX once you understand the needs and requirements of graphical applications a bit better, or if you're just really passionate about having a look at more architectural stuff.

 

The most important thing is to experiment a lot and to not worry about not getting things right immediately. Don't be intimidated by the complex looking math and such. Find sample implementations for things, play around with them, try to understand them and try to connect them mentally to their mathematical description.

 

Good luck!

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If you are focused on graphics programming, then I would suggest you try a different approach first.

 

It will take you a long time to learn enough to have a graphics framework you can experiment in if you write everything yourself.

 

I would suggest you start by looking at online sites that let you play without having to re-invent the wheel.

 

For example spend some time looking at shadertoy. Look at some of the simpler shaders until you think you understand them. Then change them and see if you are right. You can change the code in the browser and instantly see the effect your changes have had.

 

Once you are comfortable doing that, then you can start looking at what to do next.

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The most beautyful part of demoscene is, in my opinion, the old demos for ZX Spectrum , C64, and MS-DOS. That old taste is the most genuine for the Spirit of what demoscene really means. With that perspective, it is not a bad idea to use old versions of Allegro libraries (DOS) or SDL, though those are for C. For C++ we have SFML in any version. Of course may be possible to be even more rewarding to do all yourself or with little help from high level libraries, but I reccomend to be fluent in 2D before try 3D. I read very good critics about Pygame, the all famous lib for Python

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Are you trying to get into the demo scene or real-time video game graphics or offline rendering?

 

Trying to get into the demo scene, what they do is real time rendering via procedural generated graphics i believe.

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shadertoy looks really awesome. I will definetly play around with that first !

 

In regards to learning a new language, I was planning on learning a new language anyway so I really don't mind spending the extra time.

 

In your opinion, would it be better to start out with C or C++ ? I know C++ and C# are heavily used for game development, but for Demoscene, and Graphics Programming where one actually makes all his stuff, and where efficiency, size and speed are also more of a concern, then C or a Cish C++ is often used right?

 

When looking around online, some people have said that it's better to start out with C as C is a lot smaller in comparison to C++ and is stricter, which makes C a little easier to learn. But, on the other hand, there's also the opinion that starting with C sometimes makes people fall into bad habbits when they do try to write code in C++ as they often fall back to writing in a more C style code. is this true?

 

Lastly, does anyone know of any other Graphics Programming communities or forums? (other than this one of course.)

Edited by glober

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When looking around online, some people have said that it's better to start out with C as C is a lot smaller in comparison to C++ and is stricter, which makes C a little easier to learn. But, on the other hand, there's also the opinion that starting with C sometimes makes people fall into bad habbits when they do try to write code in C++ as they often fall back to writing in a more C style code. is this true?

 

Being C++ an extension of C, at the core there's really not much difference between both of them... C++ just adds new stuff to the language, abstracts some others and fixes a few little things here and there, to the point that you could almost compile C code on a C++ compiler without problems... so, by learning C you're already learning the basics of C++...

 

Also C makes you think more at the metal level, you could easily figure out the assembly produced by your code in C... and that's good... if you then move to C++ and see how it abstracted some things, you can figure out what's going on on those abstractions (nothing is pure magic), and you can decide if it's good for what you're doing or not...

 

But don't give it too much thought, as long as you understand what's going on with the code you write no matter what you learn first or after... the important thing is to take the next step in your career ;)

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Being C++ an extension of C, at the core there's really not much difference between both of them... C++ just adds new stuff to the language, abstracts some others and fixes a few little things here and there, to the point that you could almost compile C code on a C++ compiler without problems... so, by learning C you're already learning the basics of C++...

 

I really don't want to start a language war here, but this is a very common misconception. C++ is not a superset of C. It might have been at one point a long time ago, but it's absolutely not true anymore these days.

 

There's a ton of difference between C++ and C, learning C does not teach you anything about how to properly write and structure code in C++. If you go into C++ with a C mindset you'll probably just end up writing something that looks like C but with classes.

 

I'm going to leave it at this. It's really not my intention to start a language flame war.

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      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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