Chymeric Tutorials

Do awesome stuff - awesomely.

Stack Bracketed Photos

| Comments

Bracketed pictures are commonly taken to enhance the dynamic range (and sometimes the sharpness) of a photographic scene. The former type of bracketing is also known as exposure bracketing, and is what we will be dealing with in this article. There are many software products offering this functionality, including but not limited to Hugin, digiKam and Adobe Photoshop. A major drawback of these programs, however, is that they are designed mainly for graphical interface use; and will have you click through their interface for every set of bracketed images you wish to stack. Here we present a rapid and easily-batchable way to stack your exposure bracketed images via a one-liner from the command line.

1v1 Risk Strategy

| Comments

Risk is a board game, variations of which can also be played online, as for instance on Dominating12, Conquer Club, or MajorCommand. Though the gameplay mechanism is consistent, there are many variations between these websites - occasionally extending even to the rule terminology. As a general reference therefor we would recommend the succinct Dominating12 terminology glossary.

While we try to accommodate for rule variations in the following instructions, please be aware that they are meant specifically for 2-player (1v1) games (optimal gameplay is very different for multiplayer games). We follow the most popular battle mechanism, where the attacker rolls up to 3 and the defender up to 2 dice (with the defender winning ties). Our notation for attack configurations is AvD, with A being the number of attackers (troops on the attacking territory minus one) and D being the number of defenders (total troops on the defending territory).

Per-attack Risk Dice Odds

| Comments

In Risk-like games, players face off against each other on maps divided into territories. One player may conquer the territories of another by eliminating all of the other’s units from a said territory. Units can be eliminated with the throwing of the dice, and a unit is lost for every instance where the attacking player has a higher score on one cast die. The throwing of the die is governed by the following rules:

  • The defender rolls a maximum of 2 dice (one per unit - contingent on the unit number on the attacked territory).
  • The attacker rolls a maximum of 3 dice (one per unit - excluding the last unit and contingent on the unit number on the attacking territory).
  • Only the top dice are considered if a player throws more dice than his opponent.
  • Dice are paired with each other in an ordinal fashion.

There are already texts providing more wide-ranging whole-battle predictions (as for instance here), and closed-source (and in this particular case, also inaccurate) battle simulators. Here we try to offer a transparent formulaic reference and odds table for all single-attack scenarios.

Per-photo Model Release Form

| Comments

Model release forms help photographers secure the freedom to publish and sell their photography work. One common issue with model release forms (especially in the context of informal photo sessions) is that they are tailored to the practice of professional photography, and commonly grant the photographer all rights to all pictures they may have taken of the model. While for professional models this might not be an issue, for relatives, friends, and acquaintances of the photographer such a commitment becomes daunting.

Here we present a model release form concept based on encryption technology which you can use to transfer rights for single photographs.

Raspberry Pi Stage 4 Gentoo Tarball

| Comments

Tarballs (a term for .tar archives) are a common medium for installing the Gentoo Linux operating system. The standard Gentoo installation starts with a non-bootable “stage 3” tarball, which includes only very limited software. As discussed in a previous article, on the Raspberry Pi - and other embedded systems - it is in certain respects better to start off with a bootable (and wifi-capable) tarball.

For these purposes we are publishing a stage 4 tarball with all the basic software you need on the Raspberry Pi - including the sys-kernel/linux-firmware package for broad wifi-device support and a Git repository for customizing and deploying the newest Raspberry Pi kernel sources from upstream. Though the archives total under 1 GB in size, we recommend you use at least an 8 GB SD card for use with your Raspberry Pi.

Gentoo for the Raspberry Pi

| Comments

Gentoo is a Linux distribution which excels at flexibility and recommends itself for easy customization. These qualities make it especially well-suited for scientific computing or for dedicated systems. The Raspberry Pi is one of the most popular (though not the only - see Cubieboard as an alternate example) single-board computers to date, and is often deployed for dedicated tasks: scientific computing, home automation, etc.

Installing Gentoo on a dedicated platform makes it easy for the user to strip down his system to suit his needs precisely - e.g. in the guise of an ultra-minimalist installation. Here we provide an overview of current means of installing Gentoo on your Raspberry Pi.

Mkstage4 - Stage 4 Tarballs Made Easy

| Comments

Stage 4 tarballs are bootable, fully working, self-sufficient Gentoo Linux distributions. They include a complete Gento environment, which you can directly boot up and use.

Stage 4 tarballs are very well suited for system backups or use cases where chrooting and emerging your basic system requirements can become very tedious. Situations in which stage 3 installation is difficult include:

  • Installing Gentoo on machines with limited resources for compilation (e.g. many ARM family platforms)
  • Installing Gentoo for machines which do not support standard live CD/USB distributions

Free and Open Science for Your Thesis

| Comments

Topics such as open peer review, open data, and open notebook science are of increasing interest to the scientific community. Many of the concepts behind this new spin on science are rooted in the FOSS (Free and Open Source Software) world and draw credibility from its staggering success. As such, we would refer to the aforementioned set of trends in science as FOS (Free and Open Science).

With so much talk about FOS going on - and even spilling over into high-profile editorials about publication review - it is distressing how little FOS is actually taking place. Talking about the next big thing is indeed quickening, but we would rather show you how to become a part of it. And what better place to start your voyage into both academia and the FOS world than your thesis or dissertation?

Bash Cheat Sheet

| Comments

This is a collection of bash scripts solving a series of eclectic use cases which we have encountered in the past. These instructions use linux commands and directory structures.

Portage Cheat Sheet

| Comments

This is a small sample of commands dealing with a series of simple use cases involving Portage. For all the code examples please note that emerge needs to be run as root. Other commands such as equery can be run as user. The Gentoo Wiki hosts a longer (though different) Portage/Gentoo cheat sheet on this page.