Nicolas Paton npaton

The Liang-Barsky algorithm is a cheap way to find the intersection points between a line segment and an axis-aligned rectangle. It's a simple algorithm, but the resources I was pointed to didn't have particularly good explanations, so I tried to write a better one.

Consider a rectangle defined by x_min ≤ x ≤ x_max and y_min ≤ y ≤ y_max, and a line segment from (x_0, y_0) to (x_0 + Δ_x, y_0 + Δ_y). We'll be assuming at least one of Δ_x and Δ_y is nonzero.

(I'm working with Flash, so I'll be using the convention that y increases as you go down.)

We want to distinguish between the following cases:

For more information see:

pointInEllipse(test, center, width, height) {
	dx = test.x - center.x
	dy = test.y - center.y
	return ( dx * dx ) / ( width * width ) + ( dy * dy ) / ( height * height ) <= 1
}

Installing a Gem on Heroku from a Private GitHub Repo

Sometimes you want to use a gem on Heroku that is in a private repository on GitHub.

Using git over http you can authenticate to GitHub using basic authentication. However, we don't want to embed usernames and passwords in Gemfiles. Instead, we can use authentication tokens.

Get an OAuth Token from GitHub

First you will need to get an OAuth Token from GitHub using your own username and "note"

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	# source : http://code.google.com/p/natvpn/source/browse/trunk/stun_server_list
	# A list of available STUN server.

	stun.l.google.com:19302
	stun1.l.google.com:19302
	stun2.l.google.com:19302
	stun3.l.google.com:19302
	stun4.l.google.com:19302
	stun01.sipphone.com
	stun.ekiga.net

	/*************************************************
	* This is a simple Monte Carlo simulation to see
	* whether we should
	* go for X BIG deal and/or Y SMALL deals.
	*
	* What is the best blend?
	*
	* Author: Ido Green \| plus.google.com/+greenido
	* Date: 16 July 2013
	*

	func HttpConnect(proxy, url_ string) (io.ReadWriteCloser, error) {
	p, err := net.Dial("tcp", proxy)
	if err != nil {
	return nil, err
	}

	turl, err := url.Parse(url_)
	if err != nil {
	return nil, err
	}

	#cloud-config

	write_files:
	- path: /home/core/journal2logentries.sh
	permissions: '0744'
	owner: root:root
	content: \|
	#!/usr/bin/env bash
	# CoreOS on Google Compute Engine: push systemd journal logs to logentries.com
	# get your private token from logentries.com, see https://logentries.com/doc/input-token

Nicolas Paton npaton

Installing a Gem on Heroku from a Private GitHub Repo

Business Models

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Powerlevel10k

	license: gpl-3.0
	redirect: https://observablehq.com/@d3/d3-color-schemes