David | Learn C Games Programming Blog

Author: David

Building Asteroids on a Raspberry-Pi

Posted on April 17, 2020April 10, 2020 by David

Silly me completely forgot that Raspberry Pis have a different CPU architecture compared to my PC. You just get used to something working on Linux and it was only after copying and it didn’t run that I realised my mistake. So I now have to recompile Asteroids (from Chapter-48.zip).

I’ve had a Raspberry-Pi 3 B+ for a year and wanted to run the Linux asteroids on it, now that I have it working on Ubuntu.

To do that I had to setup Pi, running Raspbian downloaded from the Raspberry Pi website onto my Windows PC and then I used Win32 DiskImager (free Windows software) to burn the Raspbian OS onto a SD Card. Raspberry-Pis boot from SD Cards and the better and faster the SD card, the quicker the OS runs. Get a class 10 with A1 SD Card if you can.

After the Pi booted and Raspbian was installed and configured I had to enable SSH on the Pi; it’s disabled by default.

So now my PC was talking to the Pi using the excellent free WinSCP. I copied all the files over, including the masks, sounds and images folders and all the source code and my exe built on Ubuntu which was the wrong file type. (Trying to run Intel code on an ARM- good luck with that!)

Now it turns out that the Raspbian version I installed (I’d gone for the Raspbian Buster with desktop and recommended software-2.5 GB download) included the non-dev version of SDL2. But as I needed to recompile the whole program, I had to install Visual Studio Code, Clang and the dev versions of SDL2, image and mixer.

Visual Studio Code on Arm?

Microsoft don’t do an official version for Raspberry-Pi or other ARM boards. However I discovered that a developer called Jay Rodgers has taken their source code (VS Code is open source) and you can get a version from his site. It’s very usable on the Pi. Almost but not quite identical.

After installing the dev versions of libsdl2, image and mixer, I was almost able to compile it. I’d installed Clang but unlike the version on Ubuntu which was Clang-6, the version on Raspbian (based on Debian Buster) is Clang-7.

This means you have to edit the tasks.json file in the hidden .vscode folder. On line 25 where it says “command”: change the path to “/usr/bin/clang-7”.

That built ok, but when I ran it, it stopped with an error in the errorlog.txt file. For some reason, it failed loading the file “masks/am2.msk”. Now I’d had no errors copying files from Windows to the Pi. This had been a very intermittent problem when copying several files in one go from Windows 10 to Ubuntu running under Hyper-V. Occasionally it would come up with some weird error but usually copied OK on the second go.

Despite several attempts, I could not get it to load that mask so as a temp fix I commented the line out. This means that one of the four asteroids sizes can never collide with anything. But it now ran.

However, I’m only getting about 25-27 fps with it in the early levels, not the 60 fps that I get on Ubuntu on other hardware. Given that the bulk of the work is blitting graphics, I suspect the GPU is just a bit under powered. Apparently on the Raspberry Pi 4, the GPU is newer and twice as fast as on the 3B+ so I’ll have to try it on a 4 when I get one. But the game works and is just about playable.

Now I’ll have to try and figure out why it won’t load that one mask. This has the makings of an interesting bug…

Here’s the cover of e-book 2

Posted on April 16, 2020April 8, 2020 by David

Pretty eh! My thanks to Olivia Pro Design.

Install Clang and Visual Studio Code on Ubuntu

Posted on April 15, 2020December 2, 2020 by David

Clang is very easy to install. Open a terminal and issue this command:

sudo apt install clang

It takes a little bit more for Visual Studio Code (aka VS Code). Start on the download page of VS Code. Just google for download Visual Studio Code or click here. Click the Deb rectangle and pick the Open with Software install (default) and that will install it.

After that is installed, run VS Code (open a terminal and type code) and click the extensions icon (5th down on the left) and type in C++ in the search box. The first result is by Microsoft so select it and click install.

Now I created a Projects folder under my home, so click on open Folder in the File menu and select Projects. You can create individual folders for applications under that. If you look closely you can see Asteroids, AsteroidsDND and Examples with Asteroids being open and containing two .c files.

To compile, make sure the open tab is the file you wish to compile then click Terminal on the top menu and Run Build Task… You’ll see the compiled programs on the left under the Asteroids folder (decnot and ex1).

There’s a bit more for configuring Builds and Debugging but I’ll cover that another time.

Why C and not C++?

Posted on April 14, 2020April 5, 2020 by David

Confession, I can program in C++ though I’m a bit rusty and my C++ knowledge stops short of creating template classes but I can use them. But given that probably most games these days are programmed in C++ why is this site about C?

Well it’s been mostly personal preference. I like C; it is a heck of a lot simpler than C++ (understatement!) and compilations are very fast! I know most of C though to my chagrin I admit I got include guards wrong for quite a while. I was using them in .c files rather than .h.

Plus, I haven’t really looked into WebAssembly enough. I know it will work with both C and C++. But it has to be said that there is probably only so much you can write about C, so I will be including C++ in the future. I’d planned to do a C++ conversion of my Ebook(s).

Besides which if you google for something involving C, you’d be amazed how many C++ and even C# websites are in the results!

How I write my ebooks

Posted on April 13, 2020April 3, 2020 by David

My secret: is I use a piece of software called Jutoh from a Scottish software house. It costs £35 and if you are writing a book or e-book I highly recommend it.

Note I have no connection with them except as a very satisfied customer.

It’s all the little things, inserting pictures, tables, handling source code that make it particularly good for non-fiction books.

It also includes formatting for various programming languages and is cross-platform with versions for Linux, Mac and Windows.

The current version of the Linux e-book has 55144 words, (307407 characters). It takes about 10 seconds to compile that into a .mobi (Amazon) or .epub file with all sorts of warnings.

Originally I started writing the first e-book in a text editor then imported it to MS-Word. But Word is not exactly great software for publishing non-fiction as it’s not desktop publishing. Actually you don’t need desktop publishing per se because Kindle reflows the text, but having pictures, source code and tables makes it more complicated.

I looked about, found Jutoh and consider myself very fortunate; it makes life much easier. I’ve also had excellent support from Jutoh’s creator Dr. Julian Smart who is also well known as a creator of wxWidgets.

Writing an e-book is a multi-pass project that takes me roughly 3-4 months part-time.

Pass 1. Develop the software and e-book structure i.e. chapters.
Pass 2. Write the chapters.
Pass 3. Look for typos. For now this is just me, but eventually I hope to be able to afford a technical editor.
Pass 4. Tidy up the layout. This is probably the slowest phase. Because of the images, tables and shortish code listings, it might look neat and tidy at one size, but if you change the viewing font size, it looks er not quite so neat! I can’t see any way round that.

A friend drew the original book cover but I’ve decided to pay for the cover for the Linux version.

A little trick in Visual Studio Code

Posted on April 12, 2020April 4, 2020 by David

If you have a bit of nesting and you want to make sure your braces match up, Visual Studio code (VSC) can help you with that.

Just drag the cursor over the left or right brace and it will highlight the corresponding brace. In the screenshot you can see the brace on the 2nd line and 5th lines are highlighted.

Here’s a second trick. You can quite easily collapse code blocks. On the left below is uncollapsed code. Now move the cursor between 3 and typedef and a down arrow should appear. Click it and it will collapse the block. It now shows a right arrow and you click it to expand it back.

Made it to the end of the Linux EBook

Posted on April 11, 2020April 1, 2020 by David

Tux with books — Image by OpenClipart-Vectors from Pixabay

That is, I have completed every one of the 13 stages in the game’s development and each is up and running on Ubuntu. It turned out easier than I thought though I still need to fix one or two things.

Because Clang doesn’t support the MSVC fopen_s, I did a quick fix and removed the error checking and when it first ran, it did another segmentation fault because the high score table file didn’t exist. D’oh!

That’s fixed now. Crashing because a file is missing is a very bad practice! Also for some reason last night, Windows and Ubuntu fell out and copy/paste between them wasn’t working. It is working today. I’ve noticed this can be a little bit sensitive at times and I think it was the Windows side that fell over.

However I’ve also been playing with Ubuntu 19.10 and Copy/Paste appears to be disabled on that. That kind of thing I find extremely irritating. I have Guest services ticked, so why does nothing I do enable it? 18.04 LTS apart from last night’s glitch is perfectly happy. And 20.04 Focal Fossa (I know!) is due out on April 23rd. It’s not quite ready but you can try it an early version if you like. I will be upgrading.

Laptop vs Hyper-V

Posted on April 10, 2020March 31, 2020 by David

As a way of checking that the stuff I’m posting on GitHub, I’ve been downloading them onto a laptop and testing them.

The laptop is a seven year old Toshiba that was re-purposed from Windows to Ubuntu 18.04 LTS, the same version as I’m running in a Hyper-V session on my main development PC.

Although the laptop is older and only running an i3 chip, it still outperforms the game code running under Hyper-V code on my five year old i7-5930K PC. I think the difference is purely because the GPU code is run in a software layer not on the real GPU. But I might be wrong.

When I tested it with 255 asteroids on screen the laptop still maintained 60 fps but the Hyper-V running version dropped below 60 fps once there were 125 asteroids on screen. I have a suspicion that C code that isn’t calling any SDL routines would run faster under Hyper-V because it’s virtualised.

How to view disassembled C/C++ code in Visual Studio Code

Posted on April 9, 2020April 3, 2020 by David

There are four steps to do this. That’s assuming that you have successfully compiled your C or C++ program and have the source file handy.

Install Disassembly Explorer extension into Visual Studio Code.
Set a configuration setting.
Run a single line command in terminal.
Select a command in the Visual Studio Code command palette.

Install Disassembly Explorer.

In Visual Studio Code just switch to the extension tab and search for Dissassembly Explorer and click the install button.

Next is configuration

View the installed extensions and click the cogwheel for Disassembly Explorer then click Extension Settings at the bottom of the popup menu. A Settings tab will open, click Edit in settings.json.

You should see a few settings but only this one matters: “compilerexplorer.compilationDirectory”: “${workspaceFolder}/.vscode” . That path is where the compile etc. .json files are located.

Now open a terminal

I’ve assumed that you are running on Linux or Mac. If you are on Windows, you can also use Visual Studio Community Edition which includes disassembly features and why I’m not mentioning it here.

In the folder with your source files issue this command in the terminal.

clang -g -o asteroids.S -S asteroids.c

If OTOH you are running gcc then just substitute gcc for clang.

Finally, back in Visual Studio Code select your source file as the open tab then press F1 and in the menu that appears type in enough of Disassembly Explorer: Show until you can select it and a second tab should open with the disassembly. Click on a function in the source tab and it will jump to the correct place in the disassembled code.

Just a picture post!

Posted on April 8, 2020March 30, 2020 by David

In the chapter 42 of both e-books when the first collision detection is introduced, I added a SHOWOVERLAP #define. If this is uncommented, instead of things blowing up, it shows every pixel where two objects pixel’s overlap in bright green.

In the picture above you can see the player ship in the centre and all those green bits where things overlap. You don’t normally see this and it is so intensive that it drops the frame rate from the usual 60 fps to about 3 or 4. But I think it’s quite cool!