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OpenGL OpenGL, Versions, and the Fixed-Function Pipeline

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I'm just starting to look into the world of OpenGL. A couple of things confuse me. 1. How does the versioning work. It's not like with Direct3D where I download an SDK version. Right now, I'm just using the libraries in the Windows SDK. I know my graphics card supports OpenGL 2.0, but how do I tap into its features and such. Is it just a series of specifications, or do I need a new SDK? 2. I know the Direct3D world is getting rid of the fixed-function pipeline. Is the OpenGL community doing the same? I've noticed in all the tutorials I find, there's the PIXELFORMATDESCRIPTOR, with what looks like a lot of fixed-function settings. Is there a clean way to work around this, or should I just forget all those values? Is there any reason I should use it, and if I shouldn't, what are my guidelines for not doing so. 3. I've noticed the WGL stuff only works in WindowProc. Why is this? Is there a workaround? What if I set up an HDC and HGLRC, make them current, but never use them because my app also supports Direct3D. Would this hurt anything? Thanks for reading my post. I hope you can answer my questions.

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Original post by jbizzler
I'm just starting to look into the world of OpenGL. A couple of things confuse me.

1. How does the versioning work. It's not like with Direct3D where I download an SDK version. Right now, I'm just using the libraries in the Windows SDK. I know my graphics card supports OpenGL 2.0, but how do I tap into its features and such. Is it just a series of specifications, or do I need a new SDK?

2. I know the Direct3D world is getting rid of the fixed-function pipeline. Is the OpenGL community doing the same? I've noticed in all the tutorials I find, there's the PIXELFORMATDESCRIPTOR, with what looks like a lot of fixed-function settings. Is there a clean way to work around this, or should I just forget all those values? Is there any reason I should use it, and if I shouldn't, what are my guidelines for not doing so.

3. I've noticed the WGL stuff only works in WindowProc. Why is this? Is there a workaround? What if I set up an HDC and HGLRC, make them current, but never use them because my app also supports Direct3D. Would this hurt anything?

Thanks for reading my post. I hope you can answer my questions.


1) You can just use extensions.

2) AFAIK OpenGL:ES 2.0 doesn't support the old fixed function pipeline.

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A little more info on point #2:

Both OpenGL|ES and "Desktop" OpenGL are moving away from the fixed-function pipeline. There are future plans to provide a "lean and mean" version of OpenGL which will basically mirror the hardware implimentation of 3D hardware, with the old fixed-function model moving into an optional software layer. Other examples of things that are to be moved include Quad and Polygon primitives, for instance.


Basically, OpenGL is moving to resemble modern hardware more closely; this is what comprises the "Lean and Mean" version. Legacy features and interfaces will become optional and be implimented in software, such as drivers, which may or may not make use of the programmable pipeline (quads/n-sided primitives could be triangulated using a shader program for instance, but its not required).


Khronos.org is the new home of OpenGL, read the last issue of their Pipeline newsletter for more information.

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Quote:
Original post by jbizzler
2. I know the Direct3D world is getting rid of the fixed-function pipeline. Is the OpenGL community doing the same? I've noticed in all the tutorials I find, there's the PIXELFORMATDESCRIPTOR, with what looks like a lot of fixed-function settings. Is there a clean way to work around this, or should I just forget all those values? Is there any reason I should use it, and if I shouldn't, what are my guidelines for not doing so.

As people above said, OpenGL is moving away from the fixed function pipeline. However, PIXELFORMATDESCRIPTOR has nothing to do with OpenGL, nor with the fixed function pipeline. It's simply a Win32 structure used to define the pixel format of a rendering window.

Quote:
Original post by jbizzler
3. I've noticed the WGL stuff only works in WindowProc. Why is this?

It isn't. WGL functions work fine outside of a WinProc.

Quote:
Original post by jbizzler
What if I set up an HDC and HGLRC, make them current, but never use them because my app also supports Direct3D. Would this hurt anything?

That would be very bad. Either use OGL, or use D3D. Do not partially initialize one, and then continue with the other. This will seriously mess things up. OGL and D3D are mutually exclusive within the same application. They cannot be used simultaneously.

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1.) BAD NEWS: Unfortunately, because of the old "spec only" mentality, the current way versioning works in the API is based on the platform's implementation. For Windows, Microsoft has kept it lagging behind at OGL v1.2 for ages. And the only way to access functions of newer versions is through a slightly messy process of identifying whether the extension is supported or not by searching through a large string of available extensions on your platform. Then, manually loading all the functions associated with it via the clunky "wglGetProcAddress()". Before doing that, you'd also have to have downloaded the "glext.h" header file from opengl.org and included it in your project.

GOOD NEWS: The GLEW and GLEE libraries make this pitifully easy to work around. GLEE just loads every available extension, while GLEW lets you pick and choose the extensions you want, and/or the version of OGL you want via macros. Fortunately, the newer, more involved mentality of OpenGL promises to make the process less troublesome in future versions.

2.) The new "lean and mean" version of OGL, code-named Longs Peak, will be removing all the fixed-function capabilities and layering them on top of the core functionality.

As a clarification, the PIXELFORMATDESCRIPTOR, and the wgl* functions are part of how you configure Windows to receive and display drawing commands from OGL. It's somewhat akin to setting up the caps in D3D. Similarly, you're also setting up HDC (device context) and HGLRC (rendering context), which may look a little different, but is the same idea.

For a better idea of all this, check out NeHe's tutorials @ http://nehe.gamedev.net/ .

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I didn't know OpenGL was so active. These soon-to-be updates sound very exciting. How will they end up on my system, though? Will my graphics card just have a driver update, and I access it through extensions, or will they release their own SDK outside of the Windows SDK?

wglMakeCurrent fails if I do it anywhere outside of WindowProc's WM_CREATE. I don't know why.

If I start programming now, how different will any OpenGL future updates be? I want the cleanest, forward-looking implementation possible. Docs on OpenGL from 2000 don't look much different than they do now.

Okay, so PIXELFORMATDESCRIPTOR is a Windows thing? How does all its info affect OpenGL though? I haven't looked too deep, but why does it have stuff for depth and stencil buffers? Shoudl I just set these to zero and control them myself like I would with Direct3D 10, or do they have to match?

The extension/specs idealogy is going to take some getting used to. I just feel like when I'm reading a tutorial, like I don't know if it's the most modern, politically correct way of doing things.

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Right now, all updates are in driver revisions. The way forward for the new version is currently unclear, however the hope is that Khronos will release a lib/header set for people to link to for each platform; updates and hardware functionality will come in drivers still; the lib is likely to be a stub which just lets you talk to the hardware.

The new version (Longs Peak or LP) is going to be VERY different from the OpenGL people are used to; gone (or "emulated") are all the 'nice' functions such as glVertex, instead everything is buffers of data; however this is a Good Thing(tm) as it represents how the hardware works better which means better speed [smile]

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Some info on using GL 2.0 here, how to use it, etc.
http://www.opengl.org/wiki/index.php/Main_Page

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Okay, so I'm not the only one hoping for a header/static library package. I'd feel much cleaner that way.

Thanks everyone. I feel I have a better understandig of the world now.

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      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 reenigne
      For those that don't know me. I am the individual who's two videos are listed here under setup for https://wiki.libsdl.org/Tutorials
      I also run grhmedia.com where I host the projects and code for the tutorials I have online.
      Recently, I received a notice from youtube they will be implementing their new policy in protecting video content as of which I won't be monetized till I meat there required number of viewers and views each month.

      Frankly, I'm pretty sick of youtube. I put up a video and someone else learns from it and puts up another video and because of the way youtube does their placement they end up with more views.
      Even guys that clearly post false information such as one individual who said GLEW 2.0 was broken because he didn't know how to compile it. He in short didn't know how to modify the script he used because he didn't understand make files and how the requirements of the compiler and library changes needed some different flags.

      At the end of the month when they implement this I will take down the content and host on my own server purely and it will be a paid system and or patreon. 

      I get my videos may be a bit dry, I generally figure people are there to learn how to do something and I rather not waste their time. 
      I used to also help people for free even those coming from the other videos. That won't be the case any more. I used to just take anyone emails and work with them my email is posted on the site.

      I don't expect to get the required number of subscribers in that time or increased views. Even if I did well it wouldn't take care of each reoccurring month.
      I figure this is simpler and I don't plan on putting some sort of exorbitant fee for a monthly subscription or the like.
      I was thinking on the lines of a few dollars 1,2, and 3 and the larger subscription gets you assistance with the content in the tutorials if needed that month.
      Maybe another fee if it is related but not directly in the content. 
      The fees would serve to cut down on the number of people who ask for help and maybe encourage some of the people to actually pay attention to what is said rather than do their own thing. That actually turns out to be 90% of the issues. I spent 6 hours helping one individual last week I must have asked him 20 times did you do exactly like I said in the video even pointed directly to the section. When he finally sent me a copy of the what he entered I knew then and there he had not. I circled it and I pointed out that wasn't what I said to do in the video. I didn't tell him what was wrong and how I knew that way he would go back and actually follow what it said to do. He then reported it worked. Yea, no kidding following directions works. But hey isn't alone and well its part of the learning process.

      So the point of this isn't to be a gripe session. I'm just looking for a bit of feed back. Do you think the fees are unreasonable?
      Should I keep the youtube channel and do just the fees with patreon or do you think locking the content to my site and require a subscription is an idea.

      I'm just looking at the fact it is unrealistic to think youtube/google will actually get stuff right or that youtube viewers will actually bother to start looking for more accurate videos. 
    • By Balma Alparisi
      i got error 1282 in my code.
      sf::ContextSettings settings; settings.majorVersion = 4; settings.minorVersion = 5; settings.attributeFlags = settings.Core; sf::Window window; window.create(sf::VideoMode(1600, 900), "Texture Unit Rectangle", sf::Style::Close, settings); window.setActive(true); window.setVerticalSyncEnabled(true); glewInit(); GLuint shaderProgram = createShaderProgram("FX/Rectangle.vss", "FX/Rectangle.fss"); float vertex[] = { -0.5f,0.5f,0.0f, 0.0f,0.0f, -0.5f,-0.5f,0.0f, 0.0f,1.0f, 0.5f,0.5f,0.0f, 1.0f,0.0f, 0.5,-0.5f,0.0f, 1.0f,1.0f, }; GLuint indices[] = { 0,1,2, 1,2,3, }; GLuint vao; glGenVertexArrays(1, &vao); glBindVertexArray(vao); GLuint vbo; glGenBuffers(1, &vbo); glBindBuffer(GL_ARRAY_BUFFER, vbo); glBufferData(GL_ARRAY_BUFFER, sizeof(vertex), vertex, GL_STATIC_DRAW); GLuint ebo; glGenBuffers(1, &ebo); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,GL_STATIC_DRAW); glVertexAttribPointer(0, 3, GL_FLOAT, false, sizeof(float) * 5, (void*)0); glEnableVertexAttribArray(0); glVertexAttribPointer(1, 2, GL_FLOAT, false, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glEnableVertexAttribArray(1); GLuint texture[2]; glGenTextures(2, texture); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageOne = new sf::Image; bool isImageOneLoaded = imageOne->loadFromFile("Texture/container.jpg"); if (isImageOneLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageOne->getSize().x, imageOne->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageOne->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageOne; glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageTwo = new sf::Image; bool isImageTwoLoaded = imageTwo->loadFromFile("Texture/awesomeface.png"); if (isImageTwoLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageTwo->getSize().x, imageTwo->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageTwo->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageTwo; glUniform1i(glGetUniformLocation(shaderProgram, "inTextureOne"), 0); glUniform1i(glGetUniformLocation(shaderProgram, "inTextureTwo"), 1); GLenum error = glGetError(); std::cout << error << std::endl; sf::Event event; bool isRunning = true; while (isRunning) { while (window.pollEvent(event)) { if (event.type == event.Closed) { isRunning = false; } } glClear(GL_COLOR_BUFFER_BIT); if (isImageOneLoaded && isImageTwoLoaded) { glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glUseProgram(shaderProgram); } glBindVertexArray(vao); glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr); glBindVertexArray(0); window.display(); } glDeleteVertexArrays(1, &vao); glDeleteBuffers(1, &vbo); glDeleteBuffers(1, &ebo); glDeleteProgram(shaderProgram); glDeleteTextures(2,texture); return 0; } and this is the vertex shader
      #version 450 core layout(location=0) in vec3 inPos; layout(location=1) in vec2 inTexCoord; out vec2 TexCoord; void main() { gl_Position=vec4(inPos,1.0); TexCoord=inTexCoord; } and the fragment shader
      #version 450 core in vec2 TexCoord; uniform sampler2D inTextureOne; uniform sampler2D inTextureTwo; out vec4 FragmentColor; void main() { FragmentColor=mix(texture(inTextureOne,TexCoord),texture(inTextureTwo,TexCoord),0.2); } I was expecting awesomeface.png on top of container.jpg

    • By khawk
      We've just released all of the source code for the NeHe OpenGL lessons on our Github page at https://github.com/gamedev-net/nehe-opengl. code - 43 total platforms, configurations, and languages are included.
      Now operated by GameDev.net, NeHe is located at http://nehe.gamedev.net where it has been a valuable resource for developers wanting to learn OpenGL and graphics programming.

      View full story
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