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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:
      https://github.com/fleissna/flyEngine

      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.

      Bye,

      Phil
    • 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 ==========  
       
      Renderer.cpp
      #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; }  
      Game.zip
    • 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!
       
      Eric
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OpenGL State Change Management in D3D11

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Can anyone tell me how important state change management is, when the parameters actually do not change?

e.g. when several calls to "ID3D11DeviceContext::IASetPrimitiveTopology" are done with the same topology parameter.

Are such redundant state 'changes' handled quickly in D3D11 or should it be managed by the client program,

e.g. by just storing the parameter and then check if it must be changed or not:

StateManager::IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY topology)
{
    if (m_currentTopology != topology)
    {
        m_deviceContext->IASetPrimitiveTopology(topology);
        m_currentTopology = topology;
    }
}

That is actually what I currently do with OpenGL, to reduce the state changes. But I guess D3D11 is not such a heavy weighted state-machine as OpenGL is.

 

Thanks in advance.

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you should manage your state and only set what is needed (when it is needed). 

Depending on the rendering design, I have seen performance boost up to 15% just by managing state properly.

One think I would do differently in the code above is only actually setting the state (on the device context) just before draw/dispatch.

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State management isn’t as consequential as in OpenGL, but it still helps a bit or a lot depending on the state(s).
As mentioned above, set your states only when the draw call is issued. Otherwise it is easy to get redundant states even with your tracking method.

SetDepth( 1 );
Draw();
SetDepth( 0 ); // Just called after every draw call so that one draw call's state does not leak into another.

SetDepth( 1 );
Draw();


L. Spiro

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I would recommend filtering out redundant states. Just do yourself a favor, and don't track the current state using global variables. Global variables won't work if you every switch to an API that supports multi-threaded command list generation.

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To expand upon Spiro's point:

Don't use if-statements for state management. The if-statement alone is not free (and the D3D layer is already doing that for you, albeit behind a few more layers of abstraction/overhead). The checks also imply that your higher-level code doesn't know what state is being used and when.

For your example, if you have different topologies then that implies you're rendering rather vastly different things. Things should be rendered in like groups. e.g., render your meshes, then render your debug line overlays, etc. You never need an if-check then, because your draw code transforms like so:

// NOT GOOD
for (auto& object : objects) {
  render.set_state(object.material);
  render.draw(object);
}

// GOOD
for (auto& group : material_groups) {
  render.set_state(group.state);
  for (auto& object : group.objects)
    render.draw(object);
}

Of course, efficiently handling those groups takes some work. The gains can be quite worth it, though. Especially as it then enables automatic instancing/batching of your draw calls which keeps the hardware fed.

The hardware thing is key to remember. A lot of hardware can only run ~one program (with one set of state) at a time. If you're drawing e.g. quads, the vertex stage has all of 6 vertices to process, leaving potentially the rest of your 64-core wavegroup unused (if not the whole pipeline of hundreds or thousands of shader cores). You want all of the hardware working; you want to hand large chunks of data to the GPU and let it chew through the whole chunk in one go, rather than handing it many little chunks that it must inefficiently process sequentially. Basically, redundant state changes aren't your real problem; your renderer even making it possible to have redundant state changes in the first place is your problem. :)

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I store a 64-bit integer with all the state ID's packed into it, and then XOR two of them to see what needs to change.
e.g.

raster_mask = 0xF;
raster_shift = 42;
u64 SetRaster( u64 packed, int rasterId ) { return (packed&~(raster_mask<<raster_shift)) | (rasterId << raster_shift); }
int GetRaster( u64 packed ) { return (packed>>raster_shift) & raster_mask; }
bool HasRaster( u64 packed ) { return 0!=(packed & (raster_mask<<raster_shift)); }

u64 oldState = ..., newState = ...;
u64 dirty = oldState ^ newState;
oldState = newState;
if( HasRaster(dirty) )
  SubmitRaster(device, GetRaster(newState));

Don't use if-statements for state management. The if-statement alone is not free (and the D3D layer is already doing that for you, albeit behind a few more layers of abstraction/overhead). The checks also imply that your higher-level code doesn't know what state is being used and when.

Eh, the overhead of those if statements is some number of nanoseconds per draw on a PC. In my D3D11 engine, a draw call (including state changes for it) takes somewhere on the order of a microsecond (mostly spent inside D3D), so a few nanosecond of extra if statements is pretty negligible :wink:
I'm also not sure if D3D will do the same check internally, or if it just forwards the redundant commands onto the driver anyway.

should be rendered in like groups. e.g., render your meshes, then render your debug line overlays, etc. You never need an if-check then, because your draw code transforms like so:

You can get that grouping automatically by sorting your draw calls before you submit them.

Also, while grouping to reduce state changes is good in general, it's not always the best strategy. e.g. for alpha-blended translucency it's not even a valid solution :) or for forward-rendered opaques without a depth-pre-pass, you often want to do a coarse front to back sort combined with a least-state-changes sort within each coarse depth range.

Edited by Hodgman

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I store a 64-bit integer with all the state ID's packed into it, and then XOR two of them to see what needs to change.
e.g.

raster_mask = 0xF;
raster_shift = 42;
u64 SetRaster( u64 packed, int rasterId ) { return (packed&~(raster_mask<<raster_shift)) | (rasterId << raster_shift); }
int GetRaster( u64 packed ) { return (packed>>raster_shift) & raster_mask; }
bool HasRaster( u64 packed ) { return 0!=(packed & (raster_mask<<raster_shift)); }

u64 oldState = ..., newState = ...;
u64 dirty = oldState ^ newState;
oldState = newState;
if( HasRaster(dirty) )
  SubmitRaster(device, GetRaster(newState));

Don't use if-statements for state management. The if-statement alone is not free (and the D3D layer is already doing that for you, albeit behind a few more layers of abstraction/overhead). The checks also imply that your higher-level code doesn't know what state is being used and when.

Eh, the overhead of those if statements is some number of nanoseconds per draw on a PC. In my D3D11 engine, a draw call (including state changes for it) takes somewhere on the order of a microsecond (mostly spent inside D3D), so a few nanosecond of extra if statements is pretty negligible :wink:
I'm also not sure if D3D will do the same check internally, or if it just forwards the redundant commands onto the driver anyway.

should be rendered in like groups. e.g., render your meshes, then render your debug line overlays, etc. You never need an if-check then, because your draw code transforms like so:

You can get that grouping automatically by sorting your draw calls before you submit them.

Also, while grouping to reduce state changes is good in general, it's not always the best strategy. e.g. for alpha-blended translucency it's not even a valid solution :) or for forward-rendered opaques without a depth-pre-pass, you often want to do a coarse front to back sort combined with a least-state-changes sort within each coarse depth range.

Just a follow up question: What's the guidance on dx12 PSO state management? Individual states get merged into one PSO object, what's the strategy for cases where we have lots of objects with unique PSOs, does the switch cost related to how different two PSOs are?

 

Thanks 

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That was actually all I wanted to know:

The if-statement alone is not free (and the D3D layer is already doing that for you, albeit behind a few more layers of abstraction/overhead).

 

I know the basics of reasonable rendering state management, but I'm currently only writing a thin abstraction layer to have a unified interface for Direct3D and OpenGL.

So within this project, I have no render loops or material managment, just the basic render states.

 

Thanks and greetings,

Lukas

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