# WinFontRender - my new library
Displaying text is a common problem in graphics applications where all you can do is to render textured quads. I've implemented my solution already back in 2007, as part of my old engine The Final Quest 7, which was my master thesis. I've recently come back to this code and improved it because I needed it for the personal project I now work on. Then I thought: Maybe it's a good idea to extract this code into a library? So here it is:
It does two things:
1. It renders characters of the font to a texture, tightly packed.
2. It calculates vertices needed to render given text.
Here are more details about the library:
# Vulkan Memory Allocator Survey March 2019
Are you a software developer, use Vulkan and the Vulkan Memory Allocator library (or at least considered using it)? If so, please spend a few minutes and help to shape the future of the library by participating in the survey:
Your feedback is greatly appreciated. The survey is anonymous - no personal data is collected like name, e-mail etc. All questions are optional.
# Programming FreeSync 2 support in Direct3D
AMD just showed Oasis demo, presenting usage of its FreeSync 2 HDR technology. If you wonder how could you implement same features in your Windows DirectX program or game (it doesn’t matter if you use D3D11 or D3D12), here is an article for you.
But first, a disclaimer: Although I already put it on my “About” page, I’d like to stress that this is my personal blog, so all opinions presented here are my own and do not reflect that of my employer.
Radeon FreeSync (its new, official web page is here: Radeon™ FreeSync™ Technology | FreeSync™ 2 HDR Games) is an AMD technology that covers two different things, which may cause some confusion. First is variable refresh rate, second is HDR. Both of them need to be supported by a monitor. The database of FreeSync compatible monitors and their parameters is: Freesync Monitors.
# Programming HDR monitor support in Direct3D
I got an HDR supporting monitor (LG 32GK850F), so I started learning how I can use its capabilities programatically. I still have much to learn, as there is a lot of theory to be ingested about color spaces etc., but in this blog post I’d like to go straight to the point: How to enable HDR in your C++ DirectX program? To test this, I used 3 graphics chips from 3 different PC GPU vendors. Below you can see results of my experiments.
# How to design API of a library for Vulkan?
In my previous blog post yesterday, I shared my thoughts on graphics APIs and libraries. Another problem that brought me to these thoughts is a question: How do you design an API for a library that implements a single algorithm, pass, or graphics effect, using Vulkan or DX12? It may seem trivial at first, like a task that just needs to be designed and implemented, but if you think about it more, it turns out to be a difficult issue. They are few software libraries like this in existence. I don’t mean here a complex library/framework/engine that “horizontally” wraps the entire graphics API and takes it to a higher level, like V-EZ, Nvidia Falcor, or Google Filament. I mean just a small, “vertical”, plug-in library doing one thing, e.g. implementing ambient occlusion effect, efficient texture mipmap down-sampling, rendering UI, or simulating particle physics on the GPU. Such library needs to interact efficiently with the rest of the user’s code to be part of a large program or game. Vulkan Memory Allocator is also not a good example of this, because it only manages memory, implements no render passes, involves no shaders, and it interacts with a command buffer only in its part related to memory defragmentation.
I met this problem at my work. Later I also discussed it in details with my colleague. There are multiple questions to consider:
VK_IMAGE_USAGE_flags. If the library should allocate them internally, how should it do it? By just grabbing new pieces of
VkDeviceMemoryblocks? What if the user prefers all GPU memory to be allocated using a complex allocator of his choice, like Vulkan Memory Allocator?
VkDescriptorPool, but what if the user prefers all the descriptors to be allocated from his own descriptor pool?
vkGetDeviceProcAddr, possibly with help of something like volk? The library should be able to use those.
VkAllocationCallbacks) to all Vulkan functions? The library should be able to do it.
This is a problem similar to what we have with any C++ libraries. There is no consensus about the implementation of various basic facilities, like strings, containers, asserts, mutexes etc., so every major framework or game engine implements its own. Even something so simple as min/max function is defined is multiple places. It is defined once in
<algorithm> header, but some developers don’t use STL.
<Windows.h> provides its own, but these are defined as macros, so they break any other, unless you
#define NOMINMAX before the include… A typical C++ nightmare. Smaller libraries are better just configurable or define their own everything, like the Vulkan Memory Allocator having its own assert, vector (can be switched to standard STL one), and 3 versions of read-write mutex.
All these issues make it easier for developers to just write a paper, describe their algorithm, possibly share a piece of code, pseudo-code or a shader, rather than provide ready to use library. This is a very bad situation. I hope that over time patterns emerge of how the API of a library implementing a single pass or effect using Vulkan/DX12 should look like. Recently my colleague shared an idea with me that if there was some higher-level API that would implement all these interactions between various parts (like resource allocation, image barriers) and we all commonly agreed on using it, then authoring libraries and stitching them together on top of it would be way easier. That’s another argument for the need of such new, higher-level graphics API.
# Thoughts on graphics APIs and libraries
Warning: This is a long rant. I’d like to share my personal thoughts and opinions on graphics APIs like Vulkan, Direct3D 12.
Some time ago I came up with a diagram showing how the graphics software technologies evolved over last decades – see my blog post “Lower-Level Graphics API - What Does It Mean?”. The new graphics APIs (Direct3D 12, Vulkan, Metal) are not only a clean start, so they abandon all the legacy garbage going back to ‘90s (like
glVertex), but they also take graphics programming to a new level. It is a lower level – they are more explicit, closer to the hardware, and better match how modern GPUs work. At least that’s the idea. It means simpler, more efficient, and less error-prone drivers. But they don’t make the game or engine programming simpler. Quite the opposite – more responsibilities are now moved to engine developers (e.g. memory management/allocation). Overall, it is commonly considered a good thing though, because the engine has higher-level knowledge of its use cases (e.g. which textures are critically important and which can be unloaded when GPU memory is full), so it can get better performance by doing it properly. All this is hidden in the engines anyway, so developers making their games don’t notice the difference.
Those of you, who – just like me – deal with those low-level graphics APIs in their everyday work, may wonder if these APIs provide the right level of abstraction. I know it will sound controversial, but sometimes I get a feeling they are at the exactly worst possible level – so low they are difficult to learn and use properly, while so high they still hide some implementation details important for getting a good performance. Let’s take image/texture barriers as an example. They were non-existent in previous APIs. Now we have to do them, which is a major pain point when porting old code to a new API. Do too few of them and you get graphical corruptions on some GPUs and not on the others. Do too many and your performance can be worse than it has been on DX11 or OGL. At the same time, they are an abstract concept that still hides multiple things happening under the hood. You can never be sure which barrier will flush some caches, stall the whole graphics pipeline, or convert your texture between internal compression formats on a specific GPU, unless you use some specialized, vendor-specific profiling tool, like Radeon GPU Profiler (RGP).
It’s the same with memory. In DX11 you could just specify intended resource usage (
D3D11_USAGE_DYNAMIC) and the driver chose preferred place for it. In Vulkan you have to query for memory heaps available on the current GPU and explicitly choose the one you decide best for your resource, based on low-level flags like
VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT etc. AMD exposes 4 memory types and 3 memory heaps. Nvidia has 11 types and 2 heaps. Intel integrated graphics exposes just 1 heap and 2 types, showing the memory is really unified, while AMD APU, also integrated, has same memory model as the discrete card. If you try to match these to what you know about physically existing video RAM and system RAM, it doesn’t make any sense. You could just pick the first
DEVICE_LOCAL memory for the fastest GPU access, but even then, you cannot be sure your resource will stay in video RAM. It may be silently migrated to system RAM without your knowledge and consent (e.g. if you go out of memory), which will degrade performance. What is more, there is no way to query for the amount of free GPU memory in Vulkan, unless you do hacks like using DXGI.
Hardware queues are no better. Vulkan claims to give explicit access to the pieces of GPU hardware, so you need to query for queues that are available. For example, Intel exposes only a single graphics queue. AMD lets you create up to 3 additional compute-only queues and 2 transfer queues. Nvidia has 8 compute queues and 1 transfer queue. Do they all really map to silicon that can work in parallel? I doubt it. So how many of them to use to get the best performance? There is no way to tell by just using Vulkan API. AMD promotes doing compute work in parallel with 3D rendering while Nvidia diplomatically advises to be “conscious” with it.
It's the same with presentation modes. You have to enumerate
VkPresentModeKHR-s available on the machine and choose the right one, along with number of images in the swapchain. These don't map intuitively to a typical user-facing setting of V-sync = on/off, as they are intended to be low level. Still you have no control and no way to check whether the driver does "blit" or "flip".
One could say the new APIs don’t deliver to their promise of being low level, explicit, and having predictable performance. It is impossible to deliver, unless the API is specific to one GPU, like there is on consoles. A common API over different GPUs is always high level, things happen under the hood, and there are still fast and slow paths. Isn’t all this complexity just for nothing? It may be true that comparing to previous generation APIs, drivers for the new ones need not launch additional threads in the background or perform shader compilation on first draw call, which greatly reduces chances of major hitching. (We will see how long this state will persist as the APIs and drivers evolve.) Still there is no way to predict or ensure minimum FPS/maximum frame time. We are talking about systems where multiple processes compete for resources. On modern PCs there is even no way to know how many cycles will a single instruction take! Cache memory, branch prediction, out-of-order execution – all of these mechanisms are there in the CPU to speed up average cases, but there can always be cases when it works slowly (e.g. cache miss). It’s the same with graphics. I think we should abandon the false hope of predictable performance as a thing of the past, just like rendering graphics pixel-perfect. We can optimize for the average, but we cannot ensure the minimum. After all, games are “soft real-time systems”.
Based on that, I am thinking if there is a room for a new graphics API or top of DX12 or Vulkan. I don’t mean whole game engine with physical simulation, handling sound, input controllers and all, like Unity or UE4. I mean an API just like DX11 or OGL, on a similar or higher abstraction level (if higher level, maybe the concept of persistent “frame graph” with explicit pass and resource dependencies is the way to go?). I also don’t think it’s enough to just reimplement any of those old APIs. The new one should take advantage of features of the explicit APIs (like parallel command buffer recording), while hiding the difficult parts (e.g. queues, memory types, descriptors, barriers), so it’s easier to use and harder to misuse. (An existing library similar to this concept is V-EZ from AMD.) I think it may still have good performance. The key thing needed for creation of such library is abandoning the assumption that developer must define everything up-front, with nothing allocated, created, or transferred on first use.
See also next post: "How to design API of a library for Vulkan?"
Update 2019-02-12: I want to thank all of you for the amazing feedback I received after publishing this post, especially on Twitter. Many projects have been mentioned that try to provide an API better than Vulkan or DX12 - e.g. Apple Metal, WebGPU, The Forge by Confetti.
# Global Game Jam 2019 - my impressions
Last weekend the 2019 edition of Global Game Jam took place - a worldwide event where teams od developers gather in different sites all around the world to make games during two days and two nights. There was a large site in my city (Warsaw) - PolyJam, but I decided to go to Gda˝sk to participate it their local site called Hackerspace Game Jam together with my friends.
Theme this year was "what home means to you". As always, participants interpreted it very differently. Those who have families associated home with all kinds of troubles caused by the other residents. Pooplers - the game I liked the most - is about babies crawling around the house and pooping competitively to cover as much surface as possible with their specific color, while avoiding the mother :) Home Alone: Cat edition is about a cat that can destroy and drop stuff from the shelves, all in first person perspective. KapeŠ Defender is about a man who throws slipper (pol. "kapeŠ") at the wife and other people to be able to just sit and watch TV. There were more sci-fi settings as well. I liked the game Gwiezdni Somsiedzi a lot. It is the only one with multiplayer over network. Players have to control satellites flying in space, catch asteroids and throw them at the other players. Another space game was Glop where players have to cooperatively control various devices on the surface of a planet to make it fly, as well as shoot at incoming obstacles.
Our team was a group of friends from the demoscene - 2 ex-Intel C++ developers and 2 DevOps currently working in a bank. Unfortunately we had no graphics artists. Although I would prefer to use Unity or Unreal Engine these days, we eventually decided to go the hard way and code in C++ using dxfw - the old framework developed by Krzysiek K., based on Direct3D 9. I had to remind myself this old technology before the jam, including all these
D3DRS_ fixed-function pipeline states and D3DX math library. By the way: If the last version of DirectX SDK for DX9 was released in June 2010, can we already consider it a retro platform, along with Atari and Amiga? ;)
We used FMOD library for playing sound and music and Gainput for handling input from gamepads. We started from having a ray-traced sphere, so we had to code all the game logic and rendering from scratch, including displaying characters, UI, collisions, etc. We've developed some of the logic in C++ and some in Squirrel, because we had this scripting language already integrated with the framework. I had no previous experience with Squirrel, so I had to learn it very quickly. After going through the documentation, I concluded that I love it! It looks like a great scripting language for simple applications. It's not perfect, e.g. it lacks vector and matrix types so necessary in game development (just like pretty much every other programming language except HLSL/GLSL), but I like its simplicity and syntax. It is very similar to Lua in its overall philosophy - dynamically typed, object oriented, and based on key-value arrays. The syntax is not that weird though. It seems to follow the "principle of least astonishment" - it's very similar to C++, arrays are indexed from 0, plus ending statements with a semicolon is optional - end of line also works.
Participating in an event such as GGJ is always an adventure and an opportunity for many new experiences - much better than just sitting on the Internet at home. During this jam I not only learned Squirrel as a new programming language, but I've also heard what is it like to work as a programmer at a bank, I've registered on Asana (a web service for organizing TODO lists, just like Trello which I used before), and of course I had an opportunity to practice quick and dirty programming, as opposed to code carefully thought out and tested, like it has to be done in a regular job.
Finally, the game we've made is here: LazerBugz. It is a twin-stick shooter happening on a spherical surface of a planet. The "home" is the cosmic base that you have to defend while shooting at alien bugs and going out to gather randomly placed gems. It supports local co-op for any number of players using Xbox gamepads or keyboard and mouse. Some screenshots and a photo of people playing our game:
There was a competition on our site. We didn't take any of the first 3 places. We just got mention among the games who received a good number of votes. The game that won was Clash of T-Rexes - kind of Pong with two dinosaurs standing on two planets.
Official photo gallery from the event: Hackerspace Game Jam 2019
# Why I think it is worth studying
In 2018, it's been 10 years since I graduated Czestochowa University of Technology, becoming M.S. Computer Science. I don't regret it. There is endless debate among programmers about whether it is worth studying at some university or is it better to start professional career as early as possible and become fully self-taught specialist. Below is my personal opinion about this. (A little disclaimer: my views may be biased because my father is a professor of electrical engineering, so I had lots of contact with the scientific world since my childhood.)
One concern that arises often is the significance of having a university diploma for potential employers. From my experience, I would say that while formal education is not necessary for getting a job as a programmer, it may matter for some companies. It's important especially at the beginning of the career, when there is not much in your CV, because after many years of professional work the education takes second place after work experience. Smaller companies may favor skills and experience in specific technologies and don't require a degree too often, because they want to find an employee who can just start doing his tasks right away. Big corporations may prefer candidates with a degree because they look for talented people who can learn required skills after they are hired, plus they often have extensive HR department with people who are nontechnical and filter incoming CVs just based on keywords and simple criteria, like being a university graduate.
Another frequent question is whether the knowledge taught at the university is practical. Surely there are many courses teaching specific topics that you may never find useful in your career. Surely there is also much you will need to learn in each workplace that was not covered during the studies. It's true that software technologies evolve fast, so what you learn now may become irrelevant in few years (although not always - e.g. C has more than 40 years and it's still the 2nd most important programming language). But I think that studying gives more than just practical knowledge useful for future job, or a diploma.
1. It gives you theoretical basis. While you can learn a new programming language or a framework from a book or some materials you find on the Internet, it's not that easy with more theoretical subjects like algebra, calculus, physics, algorithms and data structures, electronics, digital signal processing etc. Would you spend long time learning these on your own, rather than focusing on something more practical? I bet most people wouldn't, while having some theoretical foundation is essential when you need to understand some practical subjects, e.g. how velocity is a derivative and acceleration is second derivative of displacement with respect to time, when programming a car simulation game.
2. It teaches you a bit of everything. For example, if your professional interests involve systems programming and C, or data science and Python, you probably prefer to deepen your knowledge in this area rather than learning about something that is less interesting to you. At the university you have to get at least some basics of various subjects, whether it's web development, databases, computer networks and security, computer hardware, operating systems and shell scripts etc. Each of these subjects may turn out to be unexpectedly useful someday, and the basic knowledge will be a good starting point for learning more about it when necessary.
3. It teaches you, and proves to others, that you are able to carry out and finish a large project. That's an important skill on its own. There are many visionary-type people with their heads full of new, high-level ideas, who start something new every day, but never finish anything, because they find it boring or too difficult to do the actual work. There are also those over-thinkers who theorize and plan everything in smallest details, but never even start doing. These are not effective employees. At university, every course is like a project. Passing exams of every semester is like a project with strict deadline. Finally, writing thesis and graduating is also like one, large project. It may be your first such big and successful accomplishment and a good start for challenges that await in your professional work.
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