整理了一下RSS和Podcast

之前Google Reader挂了之后我基本一直用Feedly，后来也开始用Google Now看新闻，用Google Podcast听Podcast。

这几天决定切换到自己的服务器上，有若干原因：

越来越不喜欢Google Now的自动推送。感觉我的眼界越来越窄。
Feedly经常遇到收费功能。
Google Podcast要关闭了。
我正好也有服务器了

RSS抓取用的Tiny Tiny RSS，这个之前就搭建好了，作为Feedly的备份。最近升级发现docker compose文件有若干变化，数据库版本也变了，稍微折腾了一下。

类似的还有几个

Miniflux
FreshRSS
NewBlur

不过这些其实都大同小异。主要Tiny Tiny RSS导入导出备份都挺方便。

手机端用的Feedme，直接支持Tiny Tiny RSS的API，也可以放Podcast

我的RSS源都很老了，有好多都没法用了，Feedly也不提示我。发现了两个不错的RSS网站

https://docs.rsshub.app/
https://feedx.net/

Podcast回头也得整理一下，不过目前问题不大。

Comments

Determine Perspective Lines With Off-page Vanishing Point

In perspective drawing, a vanishing point represents a group of parallel lines, in other words, a direction. For any point on the paper, if we want a line towards the same direction (in the 3d space), we simply draw a line through it and the vanishing point. But sometimes the vanishing point is too far away, such that it is outside the paper/canvas. In this example, we have a point P and two perspective lines L1 and L2. The vanishing point VP is naturally the intersection of L1 and L2. The task is to draw a line through P and VP, without having VP on the paper. I am aware of a few traditional solutions: 1. Use extra pieces of paper such that we can extend L1 and L2 until we see VP. 2. Draw everything in a smaller scale, such that we can see both P and VP on the paper. Draw the line and scale everything back. 3. Draw a perspective grid using the Brewer Method. #1 and #2 might be quite practical. #3 may not guarantee a solution, unless we can measure distances/p...

Chasing an IO Phantom

My home server has been weird since months ago, it just becomes unresponsive occassionally. It is annoying but it happens only rarely, so normally I'd just wait or reboot it. But weeks ago I decided to get to the bottom of it. What's Wrong My system set up is: Root: SSD, LUKS + LVM + Ext4 Data: HDD, LUKS + ZFS 16GB RAM + 1GB swap Rootless dockerd The system may become unresponsive, when the IO on HDD is persistantly high for a while. Also: Often kswapd0 has high CPU High IO on root fs (SSD) From dockerd and some containers RAM usage is high, swap usage is low It is very strange that IO on HDD can affect SSD. Note that when this happens, even stopping the IO on HDD does not always help. Usually restarting dockerd does not help, but rebooting helps. Investigation: Swap An obvious potential root cause is the swap. High CPU on kswapd0 usually means the free memory is low and the kernel is busy exchanging data between disk and swap. However, I tried the following steps, none of the...

Moving Items Along Bezier Curves with CSS Animation (Part 2: Time Warp)

This is a follow-up of my earlier article. I realized that there is another way of achieving the same effect. This article has lots of nice examples and explanations, the basic idea is to make very simple @keyframe rules, usually just a linear movement, then use timing function to distort the time, such that the motion path becomes the desired curve. I'd like to call it the "time warp" hack. Demo See the Pen Interactive cubic Bezier curve + CSS animation by Lu Wang ( @coolwanglu ) on CodePen . How does it work? Recall that a cubic Bezier curve is defined by this formula :

B (t) = (1 - t)^{3} P_{0} + 3 (1 - t)^{2} t P_{1} + 3 (1 - t) t^{2} P_{2} + t^{3} P_{3}, 0 \leq t \leq 1.

In the 2D case,

B (t)

has two coordinates,

x (t)

and

y (t)

. Define

x_{i}

to the be x coordinate of

P_{i}

, then we have:

x (t) = (1 - t)^{3} x_{0} + 3 (1 - t)^{2} t x_{1} + 3 (1 - t) t^{2} x_{2} + t^{3} x_{3}, 0 \leq t \leq 1.

So, for our animated element, we want to make sure that the x coordiante (i.e. the "left" CSS property) is \(...

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