How many holes does a straw have?
@i-send-you-random-asks
(asking you specifically cause i think you'd have an interesting answer)
Ohhh, yes, this is my question! Thank you, dear!
Short answer:
That depends on your definition of 'hole'. Topology says 1.
Long answer:
Since this depends on your definition of hole, I can think of 5 answers that can be rationalised and make some flavour of sense:
(@marvellouspinecone helped me with some of these a while back and might have additional info, so I am going to credit her here.)
0 holes
You can define a hole as something that makes an object broken, or at least as something you have to put into a finished object AFTER construction. This could be something like a tear in the fabric or a hole you have drilled into the 'wall' of the straw. Ergo, a functioning straw does not have any holes. It looks exactly as it was designed to be.
1 hole
This is the math answer. As said in the infamous post, a straw is 'topologically equivalent' to a torus. To be precise, it is homotopic to a torus.
First question: What is a torus?
Answer: Basically a donut. It looks like this:
[ID: image of a torus. It looks like a donut with a checkered surface. end ID]
Second question: What does 'homotopic' mean?
Answer: This is where it gets math-y technical, but in a way it means that we can continuously transform either of the objects into the other - in a nice way.
Imagine, our straw was made of super-clay: we can't rip it or glue it together at any point, but we can pull and push it together however we like, even changing its density. So we could stretch some parts to become very big and shrink others a lot. We can also bend and twist it a little.
So, we take our straw and we push it together in the direction of its length until the very long straw becomes short like a ring. And then we pull on the 'walls' to make them nice and fat and round. Tada! We have made a donut!
(We can do this in the other direction, too, pull the torus (donut) out long and then make the walls thin - then we get a straw.)
The thing about such homotopies is, they preserve the number of holes an object has. Hence, the straw has exactly as many holes as the torus (donut)!
Third question: How many holes does a torus have?
Answer: In topology, we have something called the Euler characteristic. It is a number that gets assigned to surfaces based on their properties (you can calculate it via triangulation but let's not go there.) A sphere (ball) has Euler characteristic 2. Each hole in a surface lowers the Euler characteristic by 2. The torus (is an orientable surface and) has Euler characteristic 0, so it has one hole.
(If you'd like to have the more exact explanation, it is attaching handles to a surface that reduce the Euler characteristic by 2 and add a hole. And a torus is homotopic to a sphere with one handle attached.)
Thus, a straw has one hole.
2 holes
If we define a hole as an indentation in an object that allows us (or something else) to enter a certain distance into the object, a straw has two holes. One on the top and one on the bottom.
This definition actually makes sense, since we call holes we dig into the Earth 'holes'. In the mathematic sense, they aren't, they're indentations that can (with the super clay idea) be flattened out. But with these holes we don't care about whether it will lead somewhere or just have a floor somewhere at the bottom, you can go in, so it's a hole.
If we forget about the fact that the straw leads 'one hole into the other', so like, if we were very small (or the straw very big) and we would merely walk across the outside and look into the holes, we would find two holes on the straw, one on the bottom, one on the top. If we don't enter, we wouldn't even know they were connected.
With this definition you have to be a little bit careful about when you start calling something a hole. I would reckon there needs to be a certain percentage-relation between depth of hole vs circumference of entrance to hole before you call it such. And maybe also something about size and shape and sharpness of edge - like, you wouldn't call a valley a hole, probably? But like, the straw fulfils the requirements of this hole easily, and twice.
3 holes
Okay, this one is merely for fun and play, don't get mad at me. But, say we define a hole kinda like above, as an entrance to the inside of an object. And we further define hole as any way through an object. Then we end up with something I like to call a 'hole-interval' through the straw.
So, we have one hole (rim at the top) to get into the straw, one hole (the straw, basically) to get through the straw and a third whole (rim at the bottom) to get out of the straw.
This is nonsense, obviously, but I like it, because there is a very nice mathematical feeling to it, resembling a closed interval. A closed interval [a, b] is just one object, but it has three parts that are often regarded independently of the others: the open interval (a, b) in the middle and the edge points {a} and {b}. For example, if you were to test the continuity of a function, you would often regard these three cases separately. So, in a way, there is beauty in regarding the 'three holes' of the straw as separate as well.
Infinitely many holes
This one is kinda nonsense as well, but I like the implications. If we define a hole as any instance of an object that is part of a tunnel through the object - I am using the word 'tunnel' here because actually, that tunnel would be the one hole in this case but for the sake of the definition, it can't be - then a straw is an infinite number of holes, stacked on top of each other. It is important to notice here that a hole cannot possibly have any depth in this case, just like the top and bottom holes in the last case.
This leads to two likely interpretations:
A) We have a hole at any real number (if we consider the straw as an interval along its length again). Then the straw would be made from uncountably infinitely many holes - which I think is an awesome concept.
B) We have a hole at any rational number. This would only give us a countably infinite number of holes in the straw and since Q is dense in R (don't worry about what that means), it would LOOK like the whole straw is made of holes, when in reality most of the straw would actually NOT HAVE ANY holes in it. Now isn't that the best thing you have heard all day?
And the best part : By this definition, not only would any straw be made of infinitely many holes, but any object with a hole in it would have infinitely many holes in it. Remember, for this to make sense, we needed to have holes with 0 depth. But any hole in reality has some depth. Punch a hole into a piece of paper: BAM infinitely many holes stacked on top of each other! :D
What have we learnt?
The most likely answers are 1 hole or 2 holes, depending on whether you take a more mathematical or more language-oriented approach. I think those were the two opinions most vocal in the original post as well.
But if you want to have fun, you can come up with very nice concepts and definitions to count holes by that give you a range of correct answers. Just make sure to think of the implications :)
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so you want to use OBS
hello! i’ve decided to compile information on my OBS setup and some resources that have helped me along the way. this is mostly for personal reference, but maybe others can make use of this information!
some notes before i get into it:
i use OBS for both offline recording and (twitch) streaming. any footage i record is edited using DaVinci Resolve 18, which is free.
most of my OBS captures are of video games (through a USB capture card, specifically elgato), and the occasional screen/application capture (like clip studio paint, and sometimes PC games).
as such, the information here is reflective of these experiences. this post is not comprehensive to all of OBS’s features- this is just an overview of the settings and configurations that are most relevant to me.
with that out of the way, all the information will be under the cut!
Basic Setup
file format:
how to change: settings -> output -> recording -> recording format -> press “apply” once finished!
I save most of my recordings as .mkv files- it supports multi-track audio! i prefer .mkv over .mp4 because if your power goes out, you still have a recording to work with.
.mkv files can be read by DaVinci Resolve without an issue- but for Adobe software, they'll need to be remuxed to .mp4 within OBS! (file -> remux recordings -> press the … to select a file -> press the “remux” button)
video resolution and framerate:
how to change: settings -> video -> output (scaled) resolution
my obs canvas is @ 1920 x 1080p (16:9)
i switch between 720p and 1080p as needed! if you're concerned about space, you can probably just go for 720p. i also record at 30 fps, simply because that’s what my capture card supports.
video bitrate:
how to change: settings -> output -> encoder settings (located in both the streaming and recording tab) -> press “apply” once finished!
bitrate is a bit of a doozy to explain, but the most important thing to know is that bitrate affects your video’s quality. lower numbers = lower quality, while higher numbers = higher quality.
generally speaking, you'll want higher bitrate when you're recording things with high depth of information (e.g. you’d want a higher bitrate for something fast-paced like splatoon, compared to a slower-paced game like animal crossing).
my video bitrate is either set to 3000 or 4000 kbps! and here's some of my other (related) settings while i'm at it:
you can put your bitrate at much higher values than me if you're a stickler for quality- but keep in mind that a higher bitrate means:
bigger file size
more information to upload (when streaming)
your computer will need to encode more
i’d recommend reading twitch’s guidelines on encoding, bitrate, resolution, and framerate to get an idea of what values to pick. for people who are doing offline recording or streaming on a different platform, i suggest googling the appropriate resources!
multi-track audio:
this is mostly applicable to anyone looking to do video editing!
multi-track audio basically allows you to separate your audio sources (e.g. discord, game audio, and your own microphone) into different tracks.
this is an immensely helpful tool because it lets you adjust audio levels in post-production (editing). some examples of how this can be used:
increasing someones microphone volume if they speak too softly
increasing/decreasing game audio
muting swear words/sensitive information
completely muting voice call + microphone if you want to upload a no commentary video
and more!
to set this up, take a look at your audio mixer panel, and press the ⚙ icon. this will bring up advanced audio properties.
by checkmarking a track box, it puts the audio on that track. to make the above screenshot easier to digest:
track 1 consists of ALL three audio sources- desktop, elgato, and microphone.
track 2 only has the microphone audio.
track 3 only has desktop audio (i use this for voice calls)
track 4 only has the elgato capture card audio (game audio). the volume has also been lowered so that any speaking voices can be heard clearly.
tracks 5 and 6 are unused.
you might be wondering, “why do all three of these have 1 checked off?” this is what i call the universal audio track. i recommend having a universal audio track for a few reasons:
when you stream from OBS onto twitch/youtube- you have to select ONE audio track.
it’s also a nice backup in case you didn’t separate your audio correctly.
if for whatever reason you need to move around your individual audio tracks in editing, the universal track acts as a nice reference point.
mark off your audio tracks for each audio source as you see fit! once you’re finished with the advanced audio properties, go to settings > output.
for the streaming tab, you’ll want to have the number of your universal audio track selected. in my case, that will be audio track 1.
for the recording tab, checkmark all the audio tracks that are applicable to you (in my case, audio tracks 1, 2, 3, and 4). by default, only audio track 1 is selected.
if you don’t check off the additional audio tracks in the output > recordings section, you will not have access to those audio tracks in editing, and you won’t be able to edit your audio tracks independently of each other. so don’t forget to do this! 👍
custom browser docks
custom browser docks are a great tool for when you’re streaming and want to have access to your twitch chat and/or activity feed! (or if you wanted to have some other web browser on OBS).
to create one, go to docks -> custom browser docks.
you’ll be given a table interface that asks you to put the dock name and URL. for streamers who want to have chat and alerts available, do the following:
on twitch’s homepage, go to the upper right and click your icon
then, click creator dashboard
once you’re on your dashboard, go to stream manager
click the vertical “...” on my chat OR activity feed.
press “pop-out chat” OR “pop-out activity feed”
copy and paste the link into the table back into OBS
press apply once you’re done
click and drag the docks around at your leisure to put them where you like!
if you ever decide you don’t want to have something on your OBS dock (or want to bring something back), go to the toolbar, click “docks,” and click the appropriate dock!
third party things
a section of optional things that you may enjoy having.
streamlabs alerts
this is basically for anyone who streams and wants to have their chat and/or follower notifications visualized on screen!
streamlab alerts can be added to OBS by adding a browser source into your scene, and the specifics can be customized on streamlabs itself. it’s pretty self-explanatory, so i’ll just leave a link to streamlabs website, where you can log in using the streaming platform of your choice: https://streamlabs.com/
discord overlay
this is a browser source that can be set up to show people who are in a server's voice chat and who speaks. i recommend this to people who make multiplayer content- it can help viewers distinguish who is who but also it can be helpful in editing.
to set this up, go to https://streamkit.discord.com/overlay, click “install for OBS,” and after logging in with discord, go to “voice widget” and click the server and voice channel you want.
you are able to apply CSS if you'd like more control over the visuals, but the standard layout tends to work fine for me! a search of “discord overlay css” on youtube can help you get more information.
veadotube mini
this is a pngtuber software that a friend recommended to me! no webcam is required- mouth opening and closing is based on your microphone input!
you can download it here (it’s pay what you want!): https://olmewe.itch.io/veadotube-mini
for a proper tutorial on how to use it, i recommend checking out the app's documentation, which you can read here: https://veado.tube/help/
source record
have you ever wanted to stream something with a chat overlay/layout, but wanted your recording to ONLY be the gameplay? or maybe you wanted to record BOTH your gameplay AND your webcam so that you can have a crisp zoom-in on your webcam!
source record is a third party plugin that can help you with that!
the general gist of source record involves applying the “source record” filter on either a scene or source, and customizing the encoding settings accordingly. the exact details of how to set it up is beyond the scope of this post, so I'll just direct people to this video instead (it was very helpful to me):
⚠ a quick note about source record: this plugin can be intense for your computer. be sure to do test recordings and the like to see what your computer can handle (and see if the recordings come out the way you like). it took me a few tests before i settled onto something i liked!
you can download and install source record here: https://obsproject.com/forum/resources/source-record.1285/
vdo.ninja
have you ever wanted to do a collaborative video or stream where you feature someone else’s video on your stream? or maybe you’re doing a multi-person streaming event! vdo.ninja is the perfect tool for you!
vdo.ninja turns your OBS virtual camera into a browser source link- which your collaborator can add on their stream! this is a new tool that i’ve added to my arsenal recently- since my friend and i are planning to stream a side order challenge together! i’ve still got to iron it out a bit more, but i like what i’ve used of it so far.
try it out for yourself at their website here (with documentation and demos available on the homepage!): https://vdo.ninja/ (no downloads required!)
ok! i’m set up! what now?
and with that, that’s all of the settings and tools that i thought would be worth mentioning! while most of my setup was written with video games in mind, some of these plugins and setups may be applicable to other types of videos (e.g. tabletop gaming with a physical camera)!
now that i’ve outlined all these settings, i have one more thing i have to say: regardless of what you're using OBS for, do a test recording before doing anything “official” with it. this recording can be as short as 30 seconds. it’s a good habit to develop that can make sure your streams/recordings turn out the way you want them to!
here are the kinds of things i like to check! it’s not an exhaustive list, but this can be a starting point:
video:
does my video look the way i want it to (and can my computer handle that)?
can my computer handle the load of encoding? - OBS will note in the bottom if the encoding is overloaded. if it can’t handle it, turn down your bitrate or adjust other encoding settings (e.g. i had to toggle psycho visual tuning OFF because it was causing lag)
this is especially the case if you're recording PC games- you don’t want to have slowdown on either your game or the recording!
audio:
are my audio sources (e.g. desktop audio and microphone) correct? - if you plug/unplug devices a lot, be sure to check this (settings -> audio).
are any of my audio sources muted? - make sure you don’t have anything on 🔇 if you don’t want it to be muted! otherwise the audio will be lost forever… (i lost my friend’s VC audio once… it was sad)
are my audio tracks separated properly? - requires you to boot up your editing software, but it's worth doing! for the test recording, just have something from all your sources playing at once, and see if your editor has things separated into tracks.
can i hear the voices clearly? or does the music and/or game overpower them?
if for whatever reason your OBS crashes, or you want more information on anything “critical” or “warning” worthy in your set-up, you can go to help > log files > upload current log file > analyze. crash logs currently can’t be analyzed by the log analyzer- but they’re a valuable tool when asking for help on the OBS forums!
and that’s all! for real, this time. i hope that some of these tools and settings can help anyone wanting to get more out of OBS. there’s definitely other things i didn’t touch upon (e.g. audio filters for noise compression, suppression, etc.), so i suggest doing your own research and trying things out!
happy recording/streaming, and thanks for reading! ✨
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