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    • By racarate
      Hey everybody!
      I am trying to replicate all these cool on-screen debug visuals I see in all the SIGGRAPH and GDC talks, but I really don't know where to start.  The only resource I know of is almost 16 years old:
      http://number-none.com/product/Interactive Profiling, Part 1/index.html
      Does anybody have a more up-to-date reference?  Do people use minimal UI libraries like Dear ImgGui?  Also, If I am profiling OpenGL ES 3.0 (which doesn't have timer queries) is there really anything I can do to measure performance GPU-wise?  Or should I just chart CPU-side frame time?  I feel like this is something people re-invent for every game there has gotta be a tutorial out there... right?
    • By Achivai
      Hey, I am semi-new to 3d-programming and I've hit a snag. I have one object, let's call it Object A. This object has a long int array of 3d xyz-positions stored in it's vbo as an instanced attribute. I am using these numbers to instance object A a couple of thousand times. So far so good. 
      Now I've hit a point where I want to remove one of these instances of object A while the game is running, but I'm not quite sure how to go about it. At first my thought was to update the instanced attribute of Object A and change the positions to some dummy number that I could catch in the vertex shader and then decide there whether to draw the instance of Object A or not, but I think that would be expensive to do while the game is running, considering that it might have to be done several times every frame in some cases. 
      I'm not sure how to proceed, anyone have any tips?
    • 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!
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OpenGL Some questions regarding PBR and Lighting in general

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So i've been learning OpenGL for a few months and i wrote a simple Engine for the sake of learning and implementing new techniques. I've implemented a considerable amount of stuff like SSAO, HDR, Bloom, Cascaded Shadow Maps, Variance Shadow Maps and so on. I recently started reading up on Physically Based Rendering and i ended up realizing that my knowledge on Lighting itself isn't very good. I live in Sri Lanka and programmers here don't even know what Graphics Programming is, so asking these questions on this forum is my only option. 


  1. What are the Ka, Kd, Ks terms in a usual Blinn-Phong shader? are they Material properties? Because some shaders represent them as floats and some as vec3s. Or is Kd equal to "max(NdotL, 0.0)" and Ks equal to "pow(max(NdotH, 0.0), 32.0)", in which case are they the 'Intensities' of each of them? Or are these 3 terms just constants meant to be controlled by artists? 
  2. In PBR, are the Kd, Ks terms determined using Metallicness and Roughness values? Because i've been reading this article : http://www.codinglabs.net/article_physically_based_rendering_cook_torrance.aspx  , and in this it says the sum of Ks and Kd cannot exceed 1.
  3. I've been trying to implement a Cook-Torrance specular following this article : http://content.gpwiki.org/index.php/D3DBook:(Lighting)_Cook-Torrance but i have some confusion regarding that. Should "pow(max(NdotH, 0.0), 32.0)" be replaced by the "Rs" term from the code on that article? Because when i tried that, the ambient light areas looked pitch black and the specular highlights were all wrong.
  4. Why does the Cook-Torrance shader in the CodingLabs article use multiple samples while the GPWiki article does not? Is it to accurately represent the distribution of light?

...and i think that's all the questions off the top of my head. Really sorry if this is a lot, but i'm still a beginner and need a lot of clarification. Anyways i hope you guys and help me out! Thanks in advance!


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1 - "K" is often used as shorthand for "constant" (konstant??). So Kd would be a material value that's multiplied with the diffuse term.

e.g. diffuse = Kd * max(NdotL, 0);


2 - "metalness" is an alternative workflow where instead of authoring "diffuse" (Kd) and "specular reflectivity" (Ks) colours, they instead author a "colour" and "metalness" values.

You then generate Kd and Ks by something like:

Kd = color * (1-metalness);

Ks = mix( vec3(0.03,0.03,0.03), color, metalness );

You don't have to use this workflow, but it's becomming popular because it's much easier for the artists to get correct results with.


3 - pow(max(NdotH, 0.0), 32.0) is the Blinn-Phong specular function, with a hard-coded "shininess" factor of 32...

That article says that their Rs term = (F*R*G)/((N•V)*(N•L)) ... and that their R term is their "specular function".


4 - there's a lot of different variations on Cook-Torrence. In that article, they call the three main terms F, R and G. In other literature you'll see them called F, D and G (i.e. R = D).

You can use different Fresnel functions, Roughness/Distribution functions, and Geometry functions, and still call it "Cook-Torrence".

Thank you so much! That cleared up a lot of things! 


In your answer to my second question, by "color" do you mean "Albedo"? And what about the values you sample from the Specular Map? Is that no longer useful with PBR? Or do you need both a Specular Map and a Roughness Map?

And is the Final Fragment Color determined like this?

FinalColor = Kd * max(NdotL, 0) + Ks * Rs + Ambient

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Not to come off a sounding rash, but those are basic lighting questions and PBR is a little more involved. How are you currently doing your lighting in your engine ? Before jumping into PBR I would begin with simple Blinn-Phong and something a simple material model.

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Not to come off a sounding rash, but those are basic lighting questions and PBR is a little more involved. How are you currently doing your lighting in your engine ? Before jumping into PBR I would begin with simple Blinn-Phong and something a simple material model.


I actually did a bit more reading and realized that my initial understanding was in fact correct, it's just the wording on some articles that threw me off and confused me a little. Until yesterday i was using Blinn-Phong, but now i got the Cook-Torrance specular working, along with Image Based Lighting. It seems to work, apart from the black spots on the edges, is it something wrong with the Fresnel? 


Edit : This is with a Roughness of 0.1. I guess i'll try a different Distribution and Geometric calculation. 





I found this very useful: https://interplayoflight.wordpress.com/2013/12/30/readings-on-physically-based-rendering/

Especially the SIGGRAPH stuff. The 2006 link is broken, but it can be found here: http://old.siggraph.org/publications/2006cn/course17.pdf


Ahh thank you!! I found those links really helpful! smile.png

Edited by Dihara.W

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