Honestly, this week was quite unproductive, speaking of new features. I managed to resolve most of the problems with textures (but it’s still WIP, there are some minor artifacts). I wrote needed geometry checks for the roads; standard intersections render correctly. The rest of the time went for some refactoring and code cleanup necessary to paint on ground tiles. Pushed 16 commits, total 107 (over 100, yay!).
Selenium is a testing tool used in web development. It emulates user behavior inside a web browser, right in front of you. It can interact with links, move the mouse and so on. As an example, we will make a script that draws a simple shape in Sketchpad. Selenium has many integrations; I will use Python and Google Chrome driver. And everything under 60 lines of code!
A quick reminder based on my experience. Recently I stumbled upon this great snippet, which lets me send graphics card a vector of data:
It is a useful one, but at first I started getting problems when calling OpenGL
drawArrays* methods. Continue reading
Previous week I mentioned road implementation. I started with rendering and got stuck a bit while handling texture atlases (search for
GL_TEXTURE_2D_ARRAY if you’re interested, I even may write an article about it). Roads are half-done then. I moved to easier stuff and made menu state and settings (in code so far). UI renders textures now; it took me quite a lot of time since I missed there is a function for loading images and wrote everything by hand at first 🙂 Use G to turn off the grid. This week I pushed 21 commits (total 91).
Recently I found out about great charting library and I’m astonished to see how easy it was to integrate it into a project. Google Charts is a free, pure-JS library. You embed the script, write about ten lines of code and it works.
Include link to library hosted by Google:
We just add the data and it works:
In this article, I will show basics of geometry shader – useful and easy to use an element of the rendering pipeline.
Geometry shaders in rendering pipeline
Here’s a simple diagram. I marked with orange the parts which we can modify using shaders (click to enlarge).
Our geometry shader goes into action after vertex and tesselation shaders, and inside we can use data passed from these previous stages. Inside our program we will set out variables and emit vertices – all this data will be passed to the vertex shader as if geometry shader was not existent. Let’s see it in action. Continue reading
This week was a bit slower than previous (I pushed 24 commits, total 70) since I needed to introduce some graphical user interface. I went with NanoVG library, which lets me draw basic shapes and text. There’s a new top bar with essential information about the city. You can place buildings now. I worked a bit with geometry to make a foundation for zoning (you assign a zone, e.g. residential, and people build if you provide media, low taxes, etc.).
Newer standards of C++ (starting with C++11) let us enhance templates with variable-length lists of types. We can create simpler method declarations with less copy-pasting.
We all know how to sum multiple numbers, huh? A possible approach:
The most interesting part is
typename... Ts in the template definition. It says the compiler that
Ts is a parameter pack (a list of types). In this function, we take the first argument and sum it with that of the rest. The only thing to remember is that
operator+ must be defined for all the types we used as an argument.
It’s just templates
You may think: “Hey, it’s just a recursion!”. It’s not. All those methods are generated at compile time and will be different ones in the sense of memory address etc. Also, it’s not possible to modify this variadic template function to receive e.g. vector contents. Vector allocates memory for contents in runtime after all the methods are generated. For parameter packs, the number of elements has to be known during compilation.
Look at the example of moving average (of last three items) below:
The output would be:
Example 2: moving average AVG(4, 16, 78) = 32.6667 AVG(16, 78, 0) = 31.3333 AVG(78, 0, 15) = 31 AVG(0, 15, -300) = -95 AVG(15, -300, 680) = 131.667
This approach won’t work for less than 3 elements, because there is no required template and compiler would not know what method to generate.
You can easily count contents of a parameter pack using
sizeof...(ts). With parameter packs, it just says how many elements are there; you will get no information about memory size, etc.
Example 3: Output Message 1 (3 more messages) Message 2 (2 more messages) Message 3 (1 more messages) Message 4
This one was pretty straightforward, I think.
That’s enough to make use of variadic templates. As an example, here’s a simple function working as a logger – it prepends message with current time. The declaration is the same as for
printf (I copied it from the reference in the beginning):
[Sun Mar 05 14:27:29 2017] Example 4: Simple logger [Sun Mar 05 14:27:29 2017] Test message 1 [Sun Mar 05 14:27:29 2017] Multiple elements 10, 152.398 [Sun Mar 05 14:27:29 2017] IO Error: Could not load file hello_variadic.txt
Variadic templates work nicely with
std::tuple and STL containers. There are also new features coming in C++17 like fold expressions. But that’s the topic for another article. You can find more here:
Every Friday I will post updates of what I did. I started eight days ago (so it was longer than a week) and pushed 46 commits (changes) to the repository. The project went from a triangle to buildings.
- Project and dependencies setup
- State manager – currently not used, but will come in handy for main menu, settings, and other screens
- Camera and input handling
- Basic renderer for chunked terrain (first textures ever) and buildings in flat shading manner (will have to add SSAO)
- Selecting fields with mouse, rendering selection on terrain
- Normals preview for debugging
- Linked UI library
It is an open source project; you can find Github repo here: https://github.com/kantoniak/konstruisto. Feel free to build and try, comment on the commits or participate in any other way. I write a game for the first time, so any tips are welcome.
If you don’t know how/don’t want to build, there are x64 binaries for Windows and Linux. I hope everything works fine, please let me know of any problems.
Q, E - rotate view Left click - select Right click and drag - move view Mouse scroll - zoom 1 - toggle normals
I would like to think of simulation part, starting with time speed. I need a little framework behind this. Another thing is geometry – buildings of different sizes, checking for collisions. Also, I wrote a lot of bad code; I would like to refactor it a bit.