• Advertisement
  • Popular Tags

  • Popular Now

  • Advertisement
  • Similar Content

    • By fleissi
      Hey guys!

      I'm new here and I recently started developing my own rendering engine. It's open source, based on OpenGL/DirectX and C++.
      The full source code is hosted on github:

      I would appreciate if people with experience in game development / engine desgin could take a look at my source code. I'm looking for honest, constructive criticism on how to improve the engine.
      I'm currently writing my master's thesis in computer science and in the recent year I've gone through all the basics about graphics programming, learned DirectX and OpenGL, read some articles on Nvidia GPU Gems, read books and integrated some of this stuff step by step into the engine.

      I know about the basics, but I feel like there is some missing link that I didn't get yet to merge all those little pieces together.

      Features I have so far:
      - Dynamic shader generation based on material properties
      - Dynamic sorting of meshes to be renderd based on shader and material
      - Rendering large amounts of static meshes
      - Hierarchical culling (detail + view frustum)
      - Limited support for dynamic (i.e. moving) meshes
      - Normal, Parallax and Relief Mapping implementations
      - Wind animations based on vertex displacement
      - A very basic integration of the Bullet physics engine
      - Procedural Grass generation
      - Some post processing effects (Depth of Field, Light Volumes, Screen Space Reflections, God Rays)
      - Caching mechanisms for textures, shaders, materials and meshes

      Features I would like to have:
      - Global illumination methods
      - Scalable physics
      - Occlusion culling
      - A nice procedural terrain generator
      - Scripting
      - Level Editing
      - Sound system
      - Optimization techniques

      Books I have so far:
      - Real-Time Rendering Third Edition
      - 3D Game Programming with DirectX 11
      - Vulkan Cookbook (not started yet)

      I hope you guys can take a look at my source code and if you're really motivated, feel free to contribute :-)
      There are some videos on youtube that demonstrate some of the features:
      Procedural grass on the GPU
      Procedural Terrain Engine
      Quadtree detail and view frustum culling

      The long term goal is to turn this into a commercial game engine. I'm aware that this is a very ambitious goal, but I'm sure it's possible if you work hard for it.


    • By tj8146
      I have attached my project in a .zip file if you wish to run it for yourself.
      I am making a simple 2d top-down game and I am trying to run my code to see if my window creation is working and to see if my timer is also working with it. Every time I run it though I get errors. And when I fix those errors, more come, then the same errors keep appearing. I end up just going round in circles.  Is there anyone who could help with this? 
      Errors when I build my code:
      1>Renderer.cpp 1>c:\users\documents\opengl\game\game\renderer.h(15): error C2039: 'string': is not a member of 'std' 1>c:\program files (x86)\windows kits\10\include\10.0.16299.0\ucrt\stddef.h(18): note: see declaration of 'std' 1>c:\users\documents\opengl\game\game\renderer.h(15): error C2061: syntax error: identifier 'string' 1>c:\users\documents\opengl\game\game\renderer.cpp(28): error C2511: 'bool Game::Rendering::initialize(int,int,bool,std::string)': overloaded member function not found in 'Game::Rendering' 1>c:\users\documents\opengl\game\game\renderer.h(9): note: see declaration of 'Game::Rendering' 1>c:\users\documents\opengl\game\game\renderer.cpp(35): error C2597: illegal reference to non-static member 'Game::Rendering::window' 1>c:\users\documents\opengl\game\game\renderer.cpp(36): error C2597: illegal reference to non-static member 'Game::Rendering::window' 1>c:\users\documents\opengl\game\game\renderer.cpp(43): error C2597: illegal reference to non-static member 'Game::Rendering::window' 1>Done building project "Game.vcxproj" -- FAILED. ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========  
      #include <GL/glew.h> #include <GLFW/glfw3.h> #include "Renderer.h" #include "Timer.h" #include <iostream> namespace Game { GLFWwindow* window; /* Initialize the library */ Rendering::Rendering() { mClock = new Clock; } Rendering::~Rendering() { shutdown(); } bool Rendering::initialize(uint width, uint height, bool fullscreen, std::string window_title) { if (!glfwInit()) { return -1; } /* Create a windowed mode window and its OpenGL context */ window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL); if (!window) { glfwTerminate(); return -1; } /* Make the window's context current */ glfwMakeContextCurrent(window); glViewport(0, 0, (GLsizei)width, (GLsizei)height); glOrtho(0, (GLsizei)width, (GLsizei)height, 0, 1, -1); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glfwSwapInterval(1); glEnable(GL_SMOOTH); glEnable(GL_DEPTH_TEST); glEnable(GL_BLEND); glDepthFunc(GL_LEQUAL); glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); glEnable(GL_TEXTURE_2D); glLoadIdentity(); return true; } bool Rendering::render() { /* Loop until the user closes the window */ if (!glfwWindowShouldClose(window)) return false; /* Render here */ mClock->reset(); glfwPollEvents(); if (mClock->step()) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glfwSwapBuffers(window); mClock->update(); } return true; } void Rendering::shutdown() { glfwDestroyWindow(window); glfwTerminate(); } GLFWwindow* Rendering::getCurrentWindow() { return window; } } Renderer.h
      #pragma once namespace Game { class Clock; class Rendering { public: Rendering(); ~Rendering(); bool initialize(uint width, uint height, bool fullscreen, std::string window_title = "Rendering window"); void shutdown(); bool render(); GLFWwindow* getCurrentWindow(); private: GLFWwindow * window; Clock* mClock; }; } Timer.cpp
      #include <GL/glew.h> #include <GLFW/glfw3.h> #include <time.h> #include "Timer.h" namespace Game { Clock::Clock() : mTicksPerSecond(50), mSkipTics(1000 / mTicksPerSecond), mMaxFrameSkip(10), mLoops(0) { mLastTick = tick(); } Clock::~Clock() { } bool Clock::step() { if (tick() > mLastTick && mLoops < mMaxFrameSkip) return true; return false; } void Clock::reset() { mLoops = 0; } void Clock::update() { mLastTick += mSkipTics; mLoops++; } clock_t Clock::tick() { return clock(); } } TImer.h
      #pragma once #include "Common.h" namespace Game { class Clock { public: Clock(); ~Clock(); void update(); bool step(); void reset(); clock_t tick(); private: uint mTicksPerSecond; ufloat mSkipTics; uint mMaxFrameSkip; uint mLoops; uint mLastTick; }; } Common.h
      #pragma once #include <cstdio> #include <cstdlib> #include <ctime> #include <cstring> #include <cmath> #include <iostream> namespace Game { typedef unsigned char uchar; typedef unsigned short ushort; typedef unsigned int uint; typedef unsigned long ulong; typedef float ufloat; }  
    • By lxjk
      Hi guys,
      There are many ways to do light culling in tile-based shading. I've been playing with this idea for a while, and just want to throw it out there.
      Because tile frustums are general small compared to light radius, I tried using cone test to reduce false positives introduced by commonly used sphere-frustum test.
      On top of that, I use distance to camera rather than depth for near/far test (aka. sliced by spheres).
      This method can be naturally extended to clustered light culling as well.
      The following image shows the general ideas

      Performance-wise I get around 15% improvement over sphere-frustum test. You can also see how a single light performs as the following: from left to right (1) standard rendering of a point light; then tiles passed the test of (2) sphere-frustum test; (3) cone test; (4) spherical-sliced cone test

      I put the details in my blog post (https://lxjk.github.io/2018/03/25/Improve-Tile-based-Light-Culling-with-Spherical-sliced-Cone.html), GLSL source code included!
    • By Fadey Duh
      Good evening everyone!

      I was wondering if there is something equivalent of  GL_NV_blend_equation_advanced for AMD?
      Basically I'm trying to find more compatible version of it.

      Thank you!
    • By Jens Eckervogt
      Hello guys, 
      Please tell me! 
      How do I know? Why does wavefront not show for me?
      I already checked I have non errors yet.
      using OpenTK; using System.Collections.Generic; using System.IO; using System.Text; namespace Tutorial_08.net.sourceskyboxer { public class WaveFrontLoader { private static List<Vector3> inPositions; private static List<Vector2> inTexcoords; private static List<Vector3> inNormals; private static List<float> positions; private static List<float> texcoords; private static List<int> indices; public static RawModel LoadObjModel(string filename, Loader loader) { inPositions = new List<Vector3>(); inTexcoords = new List<Vector2>(); inNormals = new List<Vector3>(); positions = new List<float>(); texcoords = new List<float>(); indices = new List<int>(); int nextIdx = 0; using (var reader = new StreamReader(File.Open("Contents/" + filename + ".obj", FileMode.Open), Encoding.UTF8)) { string line = reader.ReadLine(); int i = reader.Read(); while (true) { string[] currentLine = line.Split(); if (currentLine[0] == "v") { Vector3 pos = new Vector3(float.Parse(currentLine[1]), float.Parse(currentLine[2]), float.Parse(currentLine[3])); inPositions.Add(pos); if (currentLine[1] == "t") { Vector2 tex = new Vector2(float.Parse(currentLine[1]), float.Parse(currentLine[2])); inTexcoords.Add(tex); } if (currentLine[1] == "n") { Vector3 nom = new Vector3(float.Parse(currentLine[1]), float.Parse(currentLine[2]), float.Parse(currentLine[3])); inNormals.Add(nom); } } if (currentLine[0] == "f") { Vector3 pos = inPositions[0]; positions.Add(pos.X); positions.Add(pos.Y); positions.Add(pos.Z); Vector2 tc = inTexcoords[0]; texcoords.Add(tc.X); texcoords.Add(tc.Y); indices.Add(nextIdx); ++nextIdx; } reader.Close(); return loader.loadToVAO(positions.ToArray(), texcoords.ToArray(), indices.ToArray()); } } } } } And It have tried other method but it can't show for me.  I am mad now. Because any OpenTK developers won't help me.
      Please help me how do I fix.

      And my download (mega.nz) should it is original but I tried no success...
      - Add blend source and png file here I have tried tried,.....  
      PS: Why is our community not active? I wait very longer. Stop to lie me!
      Thanks !
  • Advertisement
  • Advertisement
Sign in to follow this  

OpenGL OpenGL: Working around inability to share VAOs

This topic is 385 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

I'm building a level (map) design tool using Qt, and my user interface will contain multiple different OpenGL-driven viewports. In Qt, each different viewport is created with its own context, and I currently have the application-wide setting enabled so that all contexts share resources with each other. I'm currently targeting OpenGL 4.1 core.

My current implementation uses one "render model" per map - the map's actual geometry (the "model", with planes and texture projection parameters and all that stuff) is converted when required to OpenGL-specific geometry data, which is stored and batched in the render model for that map. Each render model, for better or worse, uses a single VAO - I figured having one VAO per batch would equate to an awful lot of objects.

However, I've just learned today that VAOs cannot be shared between contexts. It's my suspicion that this is what's causing OpenGL to return INVALID_OPERATION when attempting to bind a VAO, or do any other drawing whatsoever, now that I've refactored my code to begin using multiple viewports. Helpfully, Mac doesn't give any errors at all, and just renders in incredibly confusing and undefined ways.

In theory I'd like for any viewport to be considered a rendering destination, so that a map's render model is the one location that stores all the geometry required, and can be drawn onto any renderable surface. If VAOs cannot be shared, I don't think I'll be able to store one per render model.

I have the following questions:

  • Should I be using one VAO per viewport, created when the viewport's context is initialised? Will this obstruct the population process of the render model (ie. does that have to be done in the same context)? Will the data still be shareable with other contexts/VAOs?
  • Alternatively, should I be using one VAO per batch? I'd imagine this would definitely tie the creation of the batch to one of the viewports' contexts, and I'm not sure how I'd manage that.

Share this post

Link to post
Share on other sites

Personally, I would retool everything to render in one context to four FBOs. Then have the four contexts copy the contents of those FBOs to their respective viewports. Seems like that would be a much simpler approach. I guess that won't work if you're running each context in a separate thread... if that's possible.

Edited by Promit

Share this post

Link to post
Share on other sites

OpenGL is fundamently anti threading on the client side. Sure it makes sense to use threading for a few things like big data transfers from or to the client side or shader compilation (thats really more about sync objects, and having a seperate context for the independent sync signal).

I tried to make usable threaded interface for OpenGL but there are just to many non shared objects (Even bindless texture handler states ARG! :[ ) and also the stupid behavior that you can't create sync objects without at the same time inserting them into the work queue.

I would just make one render thread. And use threaded helper functions for the few casses where it makes sense.

Also VAOs are slower except for MESA based drivers. Using old style binding and if available GL_ARB_vertex_attrib_binding and GL_ARB_multi_bind will be faster on AMD and Nvidia blob drivers. In that case you don't even use non-shared objects.

Share this post

Link to post
Share on other sites

You don't need to create multiple contexts.

You can have multiple HDC associated with the same HGLRC (GL context).
When rendering to each window, you need to do:

wglMakeCurrent( hdcWindow0, context0 );
// ... Draw ...
wglMakeCurrent( hdcWindow1, context0 );
// ... Draw ...
wglMakeCurrent( hdcWindow2, context0 );
// ... Draw ...
wglMakeCurrent( hdcWindow3, context0 );

The only caveats are:

  • All windows must have the same pixel formats (i.e. 32bpp/16bpp, MSAA settings)
  • Only use VSync on one of the windows (i.e. the last one), otherwise 4 windows with VSync in all of them will get you 15 fps (assuming a 60hz monitor).

This is far more stable and easier to work with than the clusterf*** that is working with shared contexts.

Share this post

Link to post
Share on other sites

Thanks for the prompt replies! Just for clarity, I'm not actually using different threads, just different contexts created by each of the Qt viewports. I also have one explcitly-created "background" context, which the application uses to perform tasks when viewports aren't currently active. This is to allow OpenGL-related operations to occur if there aren't actually viewports available at the time - if the user hasn't opened a viewport yet, I might still want to create VBOs and the like within the render models, or import textures and other assets.

First of all I think it would be useful for me to go and re-read the Qt OpenGL documentation, to see whether the contexts are actually physically different, or whether a single context is just shared across widgets in the way that Mathias mentioned. All I know at the moment is that a QOpenGLWidget manages its own context, and makes it current before my drawing code is called. Alternatively, Promit's method could potentially be both feasible and scalable, as I'd like to be able (in theory, performance permitting) to allow the user to create as many viewports as they wish.

Share this post

Link to post
Share on other sites

Also your render thread with the gl context does not have to be a windows even thread.



I'm not actually using different threads, just different contexts

Thats actually even worse then multiple threads each with its own context.

EDIT: I read the QT docs and they use a full blown context. So I would strongly advice to not use that!

Edited by Osbios

Share this post

Link to post
Share on other sites
Sign in to follow this  

  • Advertisement