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OpenGL Best way to get 2D overlays or images on screen (for a GUI).

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I am finally putting some effort towards my open source GUI library, which is meant to be generic but has OpenGL 3.x as the main focus for now since that's what my engine uses.

 

I decided to do away with a lot of cruft it had accumulated, doing away with OpenGL 1.5 support and focus on OpenGL 3.2+ core profile.

 

In order to keep the library generic enough that it could eventually be used with D3D, SDL or some other graphics API, I have separated the library into modules, a core, which does all graphic API (GAPI) independent operations and a renderer which does the specific API operations.

 

I keep an image buffer that represents the screen or the drawable area of the window hosting the GAPI, and the base renderer class draws lines, rects and so on to this buffer.

 

On the specific GAPI renderer, OpenGL in this case, I keep a texture object and each frame (for now, I will be doing it only when necessary later on), I issue a glTexSubImage2D with the contents of the image system buffer, then I render a quad (triangle strip really) textured with this texture over the whole screen.

 

So, I was wondering if this is the way to go or if I should be looking for some of the new fancy stuff on OpenGL 3.x+, it would be nice to keep image data entirely on the GPU, I don't think there is a simple way to access that memory for example to only change 15 pixels worth of a text caret, is there?

 

I considered keeping multiple textures (one per window/widget), but I don't know how optimal would that be, I guess as long as the window dimensions don't change much, it may be an improvement.

 

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Thanks, I read that page before, but couldn't figure out exactly how it could help, looking at it, it seems that PBO's would replace the calls to glTexSubImage, am I correct?

 

I'll look further into it.

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Ok, I see, I can create a PBO to which I would copy over my client-side pixel buffer data and then call glTexSubImage on it, which would immediately return firing the transfer from PBO to texture memory asynchronously. As the article says, this may not be much of an improvement depending on what I do after the call to glTexSubImage since it likely already copies over the client memory to do the upload.

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As a general rule, a PBO is really only useful if you don't need to do anything until a frame or more after the transfer.  Otherwise you're incurring the transfer overhead twice - once from system memory to the PBO and once from the PBO to the texture - and both must complete before you can draw anything.  You'd also have a hard time porting it to D3D as the concept of PBOs doesn't even exist there (they're not needed as the specific problems they solve don't exist in the same way).

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Yes, I was thinking about that, and thinking that maybe if I made all changes to the client buffer and fire the transfer at the end of a frame, doing a deferred render of the overlay on the next frame, in other words, fill the buffer and start the transfer, do all other rendering operations and then render the overlay, the overlay would always be a frame behind though.

 

Anyway, it seems that the way I am doing it is the way to go, I tried before using OpenGL primitives (for example use GL_LINES to draw a line, GL_QUADS to draw rectangles, etc), but that was never consistent between different graphic cards. I also tried glRasterPos and glDrawPixels, but I read somewhere that doing that was far from optimal...

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glDrawPixels can be reasonably optimal; I wouldn't rule it out.  If you've a simple enough use case (i.e. no alpha blending, no scaling) and if you match the format and type parameters to what your framebuffer uses natively (commonly GL_BGRA and GL_UNSIGNED_INT_8_8_8_8_REV), and if you remember to disable all texturing/lights/etc before issuing the call, it can do quite a fast transfer, and is probably the simplest way to get the job done.

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Well, I do support alpha blending, in fact I have a software implementation in the library to blend at the client buffer, I can't recall if this was one of the reasons to drop it.

 

I do think one of the main reasons for the drop is that with glDrawPixels I have to make the call each single frame, even if no widget changes are recorded, with a texture, if no changes are recorded, then no changes to the texture are required, no call to glTexSubImage and you can just render the overlay quad with the same texture as it was on the previous frame.

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If you look for alternative approaches, my opengl gui lib is based solely on immediate OGL calls (OGL2.x), even every single char is rendered this way. Though this is highly unoptimized, I can render 1000 gui elements this way without any problem per frame. When seeing the optimization potential (using VBO to store larger collections of elements, e.g. windows or panels), you can see, that there's a really hi-potential in here.

 

IMHO the greatest benefit of all this is the use of shaders.

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immediate OGL calls? what exactly do you mean? did you mean as I said before render lines with GL_LINES, rects with GL_QUADS, on DrawArrays/DrawElements?

 

I did that once, but it was not consistent, depending on the card nvidia/ati/intel, a line would end a pixel short or a pixel too long, an outline rect would not exactly match a filled rect, etc, even with the 0.375f pixel offset trick, I wouldn't get pixel perfect matches and would have to compensate one way or another.

 

I am not seeing any issues right now with my approach either, I am not really looking for alternatives right now, but its kind of something you don't see talked about too much, I've seen all kinds of shaders for example, but not one specific to GUI rendering, so I was just wondering if there was some sort of defacto way to do it I didn't knew about.

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immediate OGL calls?

More like single vertex calls like glColor(1,1,0,1) etc.

 

I am not seeing any issues right now with my approach either, I am not really looking for alternatives right now

There's nothing wrong with your approach.

 

but its kind of something you don't see talked about too much, I've seen all kinds of shaders for example, but not one specific to GUI rendering, so I was just wondering if there was some sort of defacto way to do it I didn't knew about.

In fact you can render your whole gui as 3d mesh (consisting of multilayered quads in front of a orthogonal camera). This way you could utilize some interesting effects, e.g. dynamic lighting of the gui, where the cursor is the light source, or automatic highlighting/bloom outlines of selected elements, gui shadows etc. This is not for pure functional guis, but it is really nice to pimp your gui visuals :)

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I see, immediate mode, there is no reason why my GUI won't work with that, but since is no longer on core profile, I decided to drop it. but you're right, the amount of vertex calls for a single quad are too few in comparison to a full mesh that immediate mode shouldn't have that much of an impact in this situation.

 

In fact you can render your whole gui as 3d mesh (consisting of multilayered quads in front of a orthogonal camera). This way you could utilize some interesting effects, e.g. dynamic lighting of the gui, where the cursor is the light source, or automatic highlighting/bloom outlines of selected elements, gui shadows etc. This is not for pure functional guis, but it is really nice to pimp your gui visuals smile.png

 

I hadn't though much about that, It is nice, and you gave me a reason to expose shaders to the user, its all pimping of the UI as you said though, what I meant was that you never see any shaders for the basic operations, for example doing the bulk of the drawing on the fragment shader rather than just effects, but I guess its not really practical, and the way to do it is still the same as it was before the dynamic shader pipeline.

 

Thanks for your help! :)

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      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
    • By TheChubu
      The Khronos™ Group, an open consortium of leading hardware and software companies, announces from the SIGGRAPH 2017 Conference the immediate public availability of the OpenGL® 4.6 specification. OpenGL 4.6 integrates the functionality of numerous ARB and EXT extensions created by Khronos members AMD, Intel, and NVIDIA into core, including the capability to ingest SPIR-V™ shaders.
      SPIR-V is a Khronos-defined standard intermediate language for parallel compute and graphics, which enables content creators to simplify their shader authoring and management pipelines while providing significant source shading language flexibility. OpenGL 4.6 adds support for ingesting SPIR-V shaders to the core specification, guaranteeing that SPIR-V shaders will be widely supported by OpenGL implementations.
      OpenGL 4.6 adds the functionality of these ARB extensions to OpenGL’s core specification:
      GL_ARB_gl_spirv and GL_ARB_spirv_extensions to standardize SPIR-V support for OpenGL GL_ARB_indirect_parameters and GL_ARB_shader_draw_parameters for reducing the CPU overhead associated with rendering batches of geometry GL_ARB_pipeline_statistics_query and GL_ARB_transform_feedback_overflow_querystandardize OpenGL support for features available in Direct3D GL_ARB_texture_filter_anisotropic (based on GL_EXT_texture_filter_anisotropic) brings previously IP encumbered functionality into OpenGL to improve the visual quality of textured scenes GL_ARB_polygon_offset_clamp (based on GL_EXT_polygon_offset_clamp) suppresses a common visual artifact known as a “light leak” associated with rendering shadows GL_ARB_shader_atomic_counter_ops and GL_ARB_shader_group_vote add shader intrinsics supported by all desktop vendors to improve functionality and performance GL_KHR_no_error reduces driver overhead by allowing the application to indicate that it expects error-free operation so errors need not be generated In addition to the above features being added to OpenGL 4.6, the following are being released as extensions:
      GL_KHR_parallel_shader_compile allows applications to launch multiple shader compile threads to improve shader compile throughput WGL_ARB_create_context_no_error and GXL_ARB_create_context_no_error allow no error contexts to be created with WGL or GLX that support the GL_KHR_no_error extension “I’m proud to announce OpenGL 4.6 as the most feature-rich version of OpenGL yet. We've brought together the most popular, widely-supported extensions into a new core specification to give OpenGL developers and end users an improved baseline feature set. This includes resolving previous intellectual property roadblocks to bringing anisotropic texture filtering and polygon offset clamping into the core specification to enable widespread implementation and usage,” said Piers Daniell, chair of the OpenGL Working Group at Khronos. “The OpenGL working group will continue to respond to market needs and work with GPU vendors to ensure OpenGL remains a viable and evolving graphics API for all its customers and users across many vital industries.“
      The OpenGL 4.6 specification can be found at https://khronos.org/registry/OpenGL/index_gl.php. The GLSL to SPIR-V compiler glslang has been updated with GLSL 4.60 support, and can be found at https://github.com/KhronosGroup/glslang.
      Sophisticated graphics applications will also benefit from a set of newly released extensions for both OpenGL and OpenGL ES to enable interoperability with Vulkan and Direct3D. These extensions are named:
      GL_EXT_memory_object GL_EXT_memory_object_fd GL_EXT_memory_object_win32 GL_EXT_semaphore GL_EXT_semaphore_fd GL_EXT_semaphore_win32 GL_EXT_win32_keyed_mutex They can be found at: https://khronos.org/registry/OpenGL/index_gl.php
      Industry Support for OpenGL 4.6
      “With OpenGL 4.6 our customers have an improved set of core features available on our full range of OpenGL 4.x capable GPUs. These features provide improved rendering quality, performance and functionality. As the graphics industry’s most popular API, we fully support OpenGL and will continue to work closely with the Khronos Group on the development of new OpenGL specifications and extensions for our customers. NVIDIA has released beta OpenGL 4.6 drivers today at https://developer.nvidia.com/opengl-driver so developers can use these new features right away,” said Bob Pette, vice president, Professional Graphics at NVIDIA.
      "OpenGL 4.6 will be the first OpenGL release where conformant open source implementations based on the Mesa project will be deliverable in a reasonable timeframe after release. The open sourcing of the OpenGL conformance test suite and ongoing work between Khronos and X.org will also allow for non-vendor led open source implementations to achieve conformance in the near future," said David Airlie, senior principal engineer at Red Hat, and developer on Mesa/X.org projects.

      View full story
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