Building a Physics Engine with C++ and Simulating Machines

[@itskittyme]

"i wrote this advanced physics simulator" "oh and then i ran into some problems with making the video" "thus i quickly built my own screen capturing software which works better than this giant open source program that's been around since 2012" okay

[@abeecee]

if this is my competition looking for swe jobs, I might as well give up now lmao

[@deathTurgenev]

Then proceeds to say, sorry the code isn't optimized, I'm not an expert

[@EmergencyTemporalShift]

To be fair, taking a bunch of screenshots is easier than physics

[@HAWXLEADER]

Getting a raw image sequence out of your renderer is NOT "better" than this giant open source thing. It just does 1 thing and does it really well.

[@atypicalambience3487]

He uses ffmpeg which does all the hard work for you. You can literally feed it image files and it will just make it into a video.

[@theDemong0d]

No sleeping here, there is a huge lack of technical content on youtube at this level, these videos are killer. Keep it up. Would love to see the deep-dive on your fluid sims for your engine project.

[@Alexander_Sannikov]

I don't think you actually realize how much effort goes into creating a video like this. "At this level" there's extremely little content on the entire youtube.

[@theDemong0d]

@@Alexander_Sannikov I'm not sure exactly how to interpret this, but I never said it was easy. Also, that is not strictly true since there is an immense amount of highly technical content on youtube, just not in the realm of individuals writing interesting things from scratch, and not laid out to present novel experiments, Sebastian Lague-style.

[@Alexander_Sannikov]

@@theDemong0d what I mean is that 99% of sebastian league style content requires much less knowledge and effort than a video like this. UPD nvm, I think I read your original post wrong. I think I read "huge lack" as "huge block", or something like that.

[@RodyDavis]

+1000

[@dnull]

well, unfortunately, views explain why there's no much tech-focused game dev vids on youtube.

[@JubaProductionsStudios]

"OBS was making me nuts, so I made my own screen recorder" this guy is a legend haha

[@magmacodes9143]

You can do too. FFMPEG has been a fairly straightforward framework for making small screen recorders for a long time now.

[@vedantkanoujia]

@@magmacodes9143 ffmpeg is most vulnerable due to multiple support of library

[@dudearlo]

xD

[@XENON2028]

@@vedantkanoujia what

[@jakosloth]

Man's living my dream lol

[@AngeTheGreat]

Useful or pointless video? You tell me :D Thanks for watching 💪

[@puppergump4117]

Very useful, I will surely use it

[@Dicklesberg]

All your stuff is incredible. You’re going to have a million subs in the next 2 years if you keep it up. My advice is to not abandon your long form content in favor of shorts. Your issue earlier with the car rendering video was that you didn’t have critical mass of viewership. Now that your channel is blowing up, a long term project requiring a lot of work will likely be rewarded even more.

[@Mocorn]

I know exactly zero about programming and still watched the whole thing. Physics are fundamentally interesting stuff :)

[@isuckatthisgame]

For me, somewhat useless now, but very prompting to revise my old, long-forgotten knowledge and to learn even more.

[@user-yy3ki9rl6i]

im learning modeling and simulations next semester and this pretty much hypes me up! thanks for the content man, you just got a new sub.

[@lukewellcash]

Your videos should seriously get more attention then they do. Awesome work!

[@AngeTheGreat]

Thank you! As long as there are people out there that like my stuff and find it useful, I'm good ✌

[@marilynlucas5128]

@@AngeTheGreat You're truly great.

[@jojodi]

Awesome stuff! Highly recommend you look into iterative techniques (Gauss-Seidel, or more complex Conjugate Gradient). They are probably in fact easier to implement than the Gaussian Elimination, and you can terminate iterative approaches when the error is low enough. Convergence rates are almost always related to conditioning of the system being solved, which will depend on what combination of constraints you have in your simulation. Note that isn't worse than the elimination case: poor conditioning also causes numerical instability in that algorithm as well.

[@AngeTheGreat]

Excellent suggestion, you definitely know your stuff! I actually did implement Gauss-Seidel but I didn't mention it in the video because I didn't want to confuse people haha... But you're right that iterative approaches are great. Next step will be to implement Conjugate Gradient since that'll be faster and also slightly more robust (for redundant constraints, etc.). Thanks for watching and thanks for the suggestion!

[@GeorgeTsiros]

@@AngeTheGreat i saw no Gauss in the video, in fact, I don't think I saw any weapon of _any_ kind!

[@GeorgeTsiros]

oooh. nice.

[@chriswalsh5925]

Hey @brandon, what do you think of LevenBerg-Marquadt (probably mis-spelled!). I have read several papers recently where they use that for solving systems (not physics) as it is supposed to be very fast and more 'optimisable', removing zeros etc. Wondering if you thought it would be good for a physics engine?

[@GeorgeTsiros]

@@chriswalsh5925 there is only one way to find out... code it and test it! :> There _should_ be implementations online, already.

[@thierrybeaulieu4403]

I've studied physics for 2 years and computer science for another 3 years. I'm already thought of doing something like that, but it's very impressive to see how well you've done it. There are so many layers of complexity to what you're showing

[@Alexander_Sannikov]

A note on implementation: your RK solver is very tightly coupled with the design of the system you're integrating. Usually it's best to try to decouple the integrator from the system itself and implement it more generically. For ordinary ODE's you just need a function that calculates a vector of derivatives from a vector of coordinates, and that's all your integrator needs. And your physics engine can _index_ into those arrays to access coordinates of any given rigid body.

[@AngeTheGreat]

Good idea! Might refactor that part, thanks for the suggestion

[@HilbertXVI]

Ordinary ordinary differential equations

[@revealingfacts4all]

He's also using public virtuals which tells me he's not very knowledgeable of c++

[@AngeTheGreat]

@@revealingfacts4all I don't claim to know it all and I like to assume that I know nothing anyway. What do you recommend I change?

[@Alexander_Sannikov]

@@revealingfacts4all I am curious as well as to why you think using public virtual functions somehow reflects his lack of C++ knowledge.

[@Cathal7707]

This is incredible. Constraint solving is stuff you do early on in an engineering degree but I never cared for it because I was always into the more computational stuff. Seeing you come at this from the computational side first has given me a whole new perspective.

[@IONYVDFC]

Interesting to see someone reviving the (at least my) experience of writing a physics engine. It was really a brain crushing journey for me to do this in the 90' with less accuracy, much less computing power, my very immature knowledge of math, let alone internet resources on this topic. But I have strong memories indeed from my eureka moment after real-time simulating a cloth, and a few weeks later seeing the same idea rendered on a Silicon Graphics cluster on a computer fair in Brussels.

[@scremeo8522]

As I'm currently preparing for an upcoming exam in numerical analysis, I find it interesting to see this really cool application of most of the methods I've learned! I'd like to write my own physics-engine right now, if I didn't have to study at the moment 😅

[@basile5490]

Just discovered your channel, and i see a lot of advanced, neat projects that really sparks my interest. This physics engine is very cool ! Im impressed to see that you make all that in C++, it genuinely makes me want to make similar stuff on a low level. That's really inspiring (even the nerdy mathematical details ! Along with the sources in the descriptions, those are the crunchy bit for me). Keeps up the awesome work !

[@AngeTheGreat]

Welcome to the channel! I try to work on projects that really challenge me and I'm glad that you enjoy my content. Hopefully my channel continues to help/inspire you in your software journey. Thanks for watching!

[@davidmc971]

KZbin algorithm please! Your content is an absolute gold mine of well explained experience in technical topics!

[@Ahsan_Fazal]

You're my new favorite KZbin content creator. WOW! This level of knowledge and expertise is something I rarely see on KZbin. KEEP UP THE GOOD WORK!!!

[@Alphaa101]

Where you are from?

[@opti12]

All this goes far over my head but it's so impressive to see someone make things like this and to share it online, even creating a screenrecorder in the meantime. Crazy!

[@Alexander_Sannikov]

Some constraints (such as rolling constraint, universal joint, etc) can be represented both as an extra body with simpler constraint attached to the bodies that you want to connect to start with, or with a more involved jacobian and no extra body. I recommend initially not wasting time implementing complex jacobians for joints that are not experiencing heavy load and implement them using just an extra body. If/when they become a problem, you can replace the extra body with a page of code for its jacobian, but they must converge to the same exact result in the limit of the extra body having zero mass.

[@AngeTheGreat]

Oh I see, might look into that. I think I might have gotten carried away with the rolling constraint, I really wanted to make it work for some reason lol

[@DBFIU]

Keep doing good work Ange, this is what youtube was made for.

[@AngeTheGreat]

Thanks 🙏

[@grevel1376]

You got a new subscriber. I arrived to your channel by a reddit post with a link to your engine simulation video, and I guess now I'm binge watching all your videos. Amazing work man.

[@theastuteangler]

probably the best video on programming I've seen

[@actuallydaneel]

every vid you make is just such a joy to watch, from the content to the editing it's just sublime. sincerely, good job.

[@AngeTheGreat]

Thank you, that means a lot to me! Glad you enjoyed it and hopefully I'll put out videos more consistently this year :)

[@actuallydaneel]

@@AngeTheGreat honestly, consistency isn't something i care about. take it at your own time and i'll enjoy whatever you put out, whenever you put it out.

[@physicist1994]

One of the most underrated channels on youtube. Subscribed immediately with notifications on. Best wishes.

[@tamp1o]

Holy hell this is one of the greatest videos I have seen, especially for your sub count. These are better than my uni degree!

[@krunkle5136]

Writing your own screen capture program? Legendary stuff.

[@JoBot__]

This is pretty much my favorite kind of content.

[@Skeffles]

These simulations look awesome! Can't wait to hear about the project you're making this for.

[@AngeTheGreat]

Thank you! The follow-up should be out within the next few weeks :)

[@stupidguy97]

Amazing quality. Subbed!

[@vintyprod]

Oh god that first animation you showed triggered my rigid body dynamics ptsd No but this video is actual gold. Thank you for making this. I’m so glad I found it. Also, thank you for including some of the math.

[@neutron417]

The perfect intersection of Physics, Computer Science and Math

[@AlexFlorias]

In the best way you’re content reminds me of those calming sessions in college studying on khan academy. Some things go over my head but your approach is so cool to watch, your content is criminally slept on!’

[@David-ng9qh]

"Oh yeah by the wa. On a completely unrelated sidenote, OBS sucks, so I made my own video capture software." legend

[@willi00willi]

I just got recommended this video today, and I am blown away! Can't wait to explore more of your channel's content

[@mastershooter64]

4:46 absolute madlad!! obs wasn't working properly and he just became thanos and was like "Fine, I'll do it myself" lmao

[@garrettjensen4817]

I think 1 of 3 people who got excited when he talked about the Runge Kutta ODE method. One of the best imo

[@willianvinagre3338]

That's an amazing project! I loved the video, even though I couldn't understand the mathematical stuff, it was still entertaining. Great job with your content, I think you should get more attention with how good your videos are made!

[@AngeTheGreat]

Thank you! Don't worry about not understanding the math immediately, I didn't either. It's one of those things where I had to really sit down and study it seriously before I understood. It's also why I didn't talk about it much in the video 😂

[@gaydogs]

man ur videos are so well made, i cant get enough of them

[@roothacker4404]

Really incredible that these type of information is available for free!

[@Jamie-il1qu]

Man, such a good video, I found it genuinely very exciting. For me, this is like the idealized form of Nova, thanks for making it!

[@rubixmc7320]

Why is it allways just linear algebra

[@TheGiantHog]

I can’t believe how you just glossed over some of the incredible work you did just to make this, easy sub man you’re killing it

[@freevbucksinthehoodprankgo4993]

I really enjoy watching your videos and trying to understand everything. I find that there is something satisfying in the way you explain things. Keep up the amazing work!

[@jroseme]

Super interesting and nice visuals to boot. It’s a relief to see an actual software application of this linear algebra stuff I’m learning.

[@fabianmuhlberger6153]

Wow, this would make a fantastic tool to teach technical mechanics. I would have loved to have an animation showing me this when learning dynamic

[@ir3turnz675]

You deserve so much more subs keep it up man

[@dragonminz602]

Absolutly loved the video. Honestly it is great to have some technical explanation. I have been writing some simple physics engines and now i know how to expand them. Many thanks

[@hicham2668]

Working on my 3D engine in C++, this level of results was always my dream. Thank you for sharing.

[@thatgaming1940]

It's almost midnight I'm tired and I'm watching someone build a Physics Engine but then he drops the word "Jacobian" and my mind shoots awake for a few minutes.

[@klibe]

the most i've done is remade 3d wireframe projection, and rotation of the camera is still not working, and you can see behind you, etc.. this is impressive and has blow my mind

[@NordicFrog]

You deserve millions of views.

[@AngeTheGreat]

Perhaps this will be the video that the algorithm blesses 🙏

[@Turbonuotti]

@@AngeTheGreat the algorithm will bless your latest engine sound simulator video, it is the most impressive work i have ever seen. Great things and huge potential in your work!

[@mani_mincraft]

Honestly, this video is highly inspirational. Heck, I have even started studying derivatives and I hope to begin learning force constraints (like you were talking about in your video) next. thank you for being so inspiring.

[@eustoliafukuyo6481]

I started to learn Vim at one work experience (who used also Linux like I did privately) and managed to finally code only with Vim. Then I got mocked on my second work experience where they hate everything except the only one thing they use (Windows and just shortcuts in IDEs) and said that I know nothing and Linux is not for Professionals (It's the first time I saw such a dirty code in a company). It felt great to watch this video and seeing that Vim is used.

[@regapasyafebriansyah9532]

I don't understand a single shit, but this man, THIS MAN IS DESERVE MORE ATTENTION

[@sripradpotukuchi9415]

really cool engine! the sims with the rolling constraint look awesome, so the tedious math was totally worth it 😅 physics aside, i really loved the visuals. great job!

[@AngeTheGreat]

I knew as soon as I started this project that rolling constraints were gonna be a thing, no matter how painful it was haha... Thanks for watching and glad you enjoyed it!

[@novidtoshow]

Great work! Just a small nit, here... There are many ways to discretise the vector system: dx/dt = f(x,t) 1 - LHS: -------------- First, we can discretise the lefthand-side using the base definition of the derivative: dx/dt = (x(t+dt) - x(t) )/dt This one-side difference is the part they call "Euler". It's first order accurate, with errors being proportional to dt^2. 2 - RHS: -------------- Where in time you choose to evaluate the RHS is also important. The Forward-Euler method evaluates the RHS at t=t, thus: (x(t+dt) - x(t))/dt = f(x,t)

[@deotexh]

Such a genius, ahhhhh, I'll probably never get there if I wanted to Good job for your hard work to have gotten to that point!

[@seesoftware]

What a madlad, obs didnt work, so he made his own version :D

[@coopercone4293]

Love this video. You had a great balance between explaining the math deep enough to understand the video, but not too deep to the point where it became a math video and not a physics engine video. I also agree with others that there's a lack of high-quality and highly technical content. I will definitely be going through some of your other videos.

[@marcus9157]

Awesome high quality video and explanation wise, I hope to see more content like this :)

[@AngeTheGreat]

Thank you! There will definitely be more content like this in the future :)

[@chriswalsh5925]

excellent, I remember trying to understand that witkin paper like 20 years ago, eventually gave up and stuck with rigid body physics for the project I was on. Nice to see someone actually got it working! Great video!

[@Aethier-lostwoods]

I'm convinced you only uploaded this as a flex. And it worked.

[@Daekanoid]

When you talked about the difficulty of differentiating the equations without making small mistakes, i got applied mechanics flashbacks. Oh god the hours I've spent trying to find the mistake only to assess that the problem was a misplaced exponent

[@PathikritGhosh007]

This is bloody brilliant, mate. Awesome video. Going through your github right now. Was looking to learn how to make something as complex as a physics engine, and this came in super handy.

[@rafaellisboa8493]

awesome video, I LOVE the mathematical explanations, differential equations are my passion.

[@CurtisHamilton101]

Really cool to see the math behind it all.

[@MrChaluliss]

Yo this is awesome. I know nothing about simulating physics, and am just now getting through the necessary maths and CS skills, so seeing it happen and actually wrapping my head around things is really amazing. Thanks for the cool video!

[@miroslavdimitrov5451]

Great work Ange. Keep it up, definitely a useful video!

[@AngeTheGreat]

Thanks Miro, glad it was useful to you and thanks for watching!

[@thomascromwell6840]

I'm amazed. I aspire to this level of work.

[@MrLP10o]

Dude, elaborate on the math part! It is nice to see the theory I've learned in University applied to create a physics engine! A video on the math explanation would be awesome

[@MScienceCat2851]

As someone who is learning C++ and is bad at math, this video is really is really giving me motiivation to continue

[@ezzzzie]

floored at the casual mention of a c++ mp4 capture software being created because obs was dropping frames

[@AngeTheGreat]

It's actually not that hard, I just used the same encoder used in OBS and did some basic thread synchronization to get it to work in real-time. Thanks for watching!

[@ezzzzie]

@@AngeTheGreat just the fact that you've given yourself all the prerequisite knowledge necessary to to look at up, and understand exactly how to implement it in your own project is still flooring me. you've like minmaxed for useful coding skills and creative problem solving. incredible stuff, great job, looking forward to your next upload!

[@alfonsodonotsi6691]

This is amazing!!!

[@isaacenquist]

You can try using a symplectic integrator such as velocity verlet to increase numerical stability so that the energy/system does not diverge over time.

[@syntropy3020]

This is epic. Well done. Look forward to seeing more on this.

[@travezripley]

This is amazing, This video and the Engine video… Pretty much blew my mind.

[@bigthought6351]

I don't understand why my English is week but you are explained is amazing 😃😃😃

[@royhouwayek7892]

commenting to boost engagement because wow this is awesome

[@lunchdotbox]

4:48 so i “just” made my own version, this guy is a god

[@Tantandev]

This was super entertaining! really cool project

[@AngeTheGreat]

Thank you! I've seen some of your videos too and love your work.

[@teachd.marshal1066]

Long time no see, i've been waiting for ur video since i discovered this channel

[@AngeTheGreat]

Your wait is over! Thanks for watching 🙏

[@Norman_Fleming]

I think you may have broke my brain with this one. However. The fact you made a video encoder cause you needed one to record the video. Casual flex ;)

[@RenkoGSL]

I'm sorry but that is so dumb funny. "Well, OBS pissed me off. " C++ programmer turns it into a thread. lol I love it

[@lorincszabo7411]

this was the most informative video on the subject i've ever seen :) triple thumbs up

[@zgrpro]

this is literally insane!

[@thebundieaussie8629]

This did make me go to sleep, but it was 12:30 at night, however, I woke up and rewatched it because it was so interesting

[@kdashi5747]

I'd love to see a video about your Vim setup!

[@henrydane6702]

This was absolutely incredible -- keep it up!

[@resolversoftware5088]

Man this is tremendous!! It will be great if you make some tutorial series explaining in detail how build similar engine at least on basic level! Amazing information on your channel!

[@MrAman47]

Great video, hope to see more of you!

[@spyrex3988]

dawg u are so smart it is insane

[@xsense2012]

If someone clicks on a video with this title and is bored with technical details, its their problem, 100%.

[@saritasahu6293]

C++ Developer are so cool. I don't think any Physics teacher of my shool could ever imagine, something like this can be done with, what they teach at school.

[@kloude_a4528]

awesome content! gets me inspire in a big way keep on keeping on!)

[@D43vil]

And this is why you need to learn code kids....this is wizard level

[@j.j.maverick9252]

very useful and really clear explanations. I think you judged the line between enough explanation vs too much maths exactly correct (for me anyhow!)

[@AngeTheGreat]

I spent a lot of time trying to determine where to draw that line haha... I'm glad that I got it right for at least some people, thanks a lot for watching and commenting!

[@lylesloth1275]

subscribed, epic guy, likes learning things, good at sharing things, good at explaining, epic, video liked.

[@t3v727]

I finally had some time to watch the video as well. You really made some cool stuff Ange. I realized that my maths got a bit rusty though but you made me excited about trying something into the direction of physics in games as well. Maybe it would be also a good idea to make a maths course for (game/graphics) programmers, too.

[@AngeTheGreat]

The math looks a bit scary but it actually isn't that bad! I'm excited to get flexed on by your next physics project lol. Also I might look into your idea for making a video about 3D math. Thanks for watching!

[@gavinscience4146]

“OBS was really annoying me, so I just *made my own*” “What?” “You heard me”

[@maurosampietro9900]

This guy is a good coder

[@JimboMack]

Thanks a lot, found your channel today and now im in a C++ rabbit hole for the next 48 hours at least 😂 great video, with down to earth rational explanations 👌

[@h-a-y-k4149]

This is actually a great tool for schools.

[@DctrBread]

great video, i was looking into setting up a simulated double pendulum as a learning exercise, but after thinking it through for a bit i realized i would need to know more math.