Piero V.

Some tricks with range-diff

The workflows we use for Tor Browser are kinda peculiar.

When you manage a fork, you need a strategy to stay updated with upstream. We create a new branch for every new Firefox release and cherry-pick our previous commits on top of it.

The advantage over merging is that our patches always stay in a single and compact block of commits. So, it is trivial to tell our commits from upstream, and users can easily verify we do not modify Firefox outside those commits (we keep the commit hashes of gecko-dev, the official GitHub mirror of Mozilla's mercurial repositories).

There are also disadvantages: keeping fewer commits helps with this workflow. Therefore, our commits have a meaning of “feature”, not of “change”. Thus, we constantly update them, and the history of a patch becomes hard to follow.

And most importantly, this workflow requires frequent rebases, with the risk of losing some changes. To mitigate it, every new branch goes through a review process before we switch to it.

The main tools we use are git range-diff to check single commits and “diff-of-diffs” to check the patch set as a whole. … [Leggi il resto]

Customize NSIS MUI2's welcome page

Recently, I had to customize NSIS installers for work.

It was my first time, and I had to get to know this tool first. While this system already offers many functionalities, if you want to change anything in its built-in pages, you must rely on Win32 APIs.

The welcome and finish pages are an exception, up to a certain sense, because they are made with nsDialogs, NSIS’s plugin for creating completely custom pages.

As a result, it is possible to pass to add new widgets using the same API in a function passed MUI_PAGE_CUSTOMFUNCTION_SHOW. However, I encountered a major problem: the default widgets fill the available space. Therefore, any new widgets will be hidden, and it will not be possible to interact with them with the mouse. I looked for a solution online - NSIS is more than 20 years old, so you can find a lot of documentation - but I did not find an answer that worked for me.

Eventually, I found that you can resize widgets on Win32 with MoveWindow. … [Leggi il resto]

RealSense D400 and infrared streams

A while ago, I started working on a dataset I captured a few years ago with a Microsoft Kinect One.

I immediately realized the data looked much cleaner than the newer datasets I created with my Intel RealSense D435.

I had already noticed that, above a certain distance, the depth data was full of craters. I already knew the error is proportional to the squared distance, but for me, it was much bigger than expected. Therefore, I calibrated the sensors and now I stay closer to my targets during the acquisitions.

But for the last dataset I captured, I tried another strategy: I decided to save also the raw IR footage to process it offline.

Stereo vision

RealSense cameras are RGBD sensors: they provide simultaneously a color (RGB) and depth (D) stream.

There are several types of techniques to measure depth. For example, the original Kinect for the Xbox 360 uses “structured light”, and the Kinect One included a time-of-flight camera.

The RealSense D400 series is based on stereo vision, which works by matching the same point in frames captured by two different cameras. There is a relation between the displacement of this point (disparity), the relative position of the two cameras, and the depth. … [Leggi il resto]

My RGBD toy box

In the last few months, in my free time, I have been developing a small application to elaborate RGBD datasets capturing people. In particular, my goal is to create 3D scans of heads. I do not expect these models to be well-made or even usable without some processing, but I wonder if I can transform this data at least to starter models.

I first started to work with RGBD cameras during my internship at Altair. At the time, I built a small pipeline to reconstruct models based on Kinect Fusion.

Sadly, Kinect Fusion is an online method. The advantage is that it will give immediate feedback if it loses the camera tracking. But the disadvantage is that it needs a pretty powerful GPU. I have one on my desktop, but I took all my datasets using laptops.

Also, in my experience, getting a usable dataset with Kinect Fusion requires several attempts and time (the acquisition must proceed very slowly), which, generally speaking, is not always compatible with… people 😄️. They might move, or lose patience, etc etc… … [Leggi il resto]

Un tuffo nel passato

Devo ammettere di essere un po’ un accumulatore.

In tanti anni, non ho mai buttato via i miei computer vecchi, pur sapendo che realisticamente non li riaccenderò mai. Soprattutto quelli degli anni ‘90, che sono potenziali bombe a causa della piaga dei condensatori. Ma alla fine ho deciso di buttare via quelli che un tempo erano stati protagonisti della categoria muletto di questo sito.

Prima, però, ho deciso di creare un’immagine dei loro dischi. E, dato che c’ero, ho deciso di avviarle con Qemu per vedere cosa avevo lasciato dentro.

Il primo computer era dotato di un Pentium MMX. Probabilmente risaliva a circa il 1996, ma non sono troppo sicuro perché mi è stato donato da una conoscente di famiglia, che altrimenti lo avrebbe buttato. Se ben ricordo, aveva 64MB di RAM, che io avevo portato a 128MB (di più non supportava). Mi sembra che proprio per comprarla fossi andato per la prima volta alla fiera dell’elettronica di Pordenone. E quella volta avevo comprato anche la scheda wireless Edimax EW-7128g, che mi aveva fatto tribolare non poco. … [Leggi il resto]