Save the penguin! (Ludum dare jam 46)

It’s been some months I am only writing code for work (I am going to post soon about the cool things we are doing there) and have stopped the hobby projects. But this weekend (that was Easter for Greeks) there was a Ludum Dare jam with theme “Keep it alive”. Easter in quarantine was the perfect time for a break. 🙂

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Holy-Days experiments 🌊 🌴 🌞 (Installing TempleOS/Holy-C on VirtualBox)

This post is mostly instructions on how to install the Temple OS on Debian using VirtualBox. Temple OS is an operating system written from scratch by Terry A. Davis in order to make programming and the creation of games more fun. Its shell is a Holy-C compiler where users can write commands in Holy-C and see the generated assembly. Temple OS lacks networking and security. Every program runs in ring-0 mode, which means that it has full access to the hardware. This is on purpose, “because it’s fun”. As Terry said, he didn’t want to write another UNIX and his goal was to create a modern Commodore64-like OS where the users can start writing code immediately after boot. If you are not familiar with the Temple OS and Terry A. Davis’s story, you can check the links at the end of this post.

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A simple pixel shader viewer

In a previous post, I wrote about Vkrunner, and how I used it to play with fragment shaders. While I was writing the shaders for it, I had to save them, generate a PPM image and display it to see the changes. This render to image/display repetition gave me the idea to write a minimal tool that automatically displays my changes every time I save the file with the shader code and use it when the complexity of the scene is increasing. And so, I’ve written sdrviewer, the minimal OpenGL viewer for pixel shaders of the video below:

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Having fun with Vkrunner!

Vkrunner is a Vulkan shader testing tool similar to Piglit, written by Neil Roberts. It is mostly used by graphics drivers developers, and was also part of the official Khronos conformance tests suite repository (VK-GL-CTS) for some time [1]. There are already posts [2] about its use but they are all written from a driver developer’s perspective and focus on vkrunner’s debugging capabilities. In this post, I’m going to show you an alternative use I’ve found for it, in order to have fun with pixel shaders during my holidays! 🙂

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A system to reject phone calls from my laptop

This post is about a system we devised and set up at home for me to be able to reject all the annoying phone calls I receive during the day from my laptop, without having to go pick up the phone. If you are also working from home like I do (yes, this is another cool option we have at Igalia!) you might find this hack useful. 😀


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Hair simulation with a mass-spring system (punk’s not dead!)

Hair rendering and simulation can be challenging, especially in real-time. There are many sophisticated algorithms for it (based on particle systems, hair mesh simulation, mass-spring systems and more) that can give very good results. But in this post, I will try to explain a simple and somehow hacky approach I followed in my first attempt to simulate hair (the mohawk hair of the video below) using a mass-spring system.


The code can be found here:

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A terrain rendering approach (part 1)

There are several methods to create and display a terrain, in real-time. In this post, I will explain the approach I followed on the demo I’m writing for my work at Igalia. Some work is still in progress.

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A helloworld kernel module

Today, I experimented with the linux kernel modules for the first time and I’ve written a simple module that prints a message (helloworld :P) every time that someone reads from the /dev/ktest (a custom character device) and counts how many times the device was opened for reading.

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Morphing test

So far, I hadn’t try to morph 3D objects to other 3D objects and I thought it’s something tricky to do. Today, I realized how simple and easy it is when I wrote this small test:

If you carefully choose the 3D models to have the same number of polygons, and to meet a few topological requirements, then you only need to interpolate the values of the meshes’ vectors, normals (and materials, textures, whatever you need) and draw the intermediate mesh every time. As interpolation parameter you can choose the values of a positive function that varies from 0 to 1 and backwards (I used (sin(msecs/factor) + 1)/2) to have that continuously changing effect. And that’s all!

The test is here: and it includes an obj with a scene with 3 meshes that meet the morphing requirements  (I only used the first two meshes here).