Andy Rundquist

shows perspective calculation of a line of latitude in 5-point perspective along with a perfect circle

I'm learning how to do 5- and 6-point perspective drawing. I was curious if the arcs to the vanishing points are true portions of a circle. I think I've convinced myself that they're not. Here's an overlay of my calc in blue and the suggested circle in red. They don't match!

Photo Journeys I went on a bike camping trip last week and before I left I built something to show my friends and family my trip. I wanted to capture what I built here for my future self who can’t remember …

I wrote a blog post to help my future self remember how to collect timestamped and geostamped photos while on trips and display them on an interactive map I can share
arundquist.wordpress.com/2025/06/02/p...

Rolling without slipping on curved surfaces I’ve been trying to see if I can model balls rolling on curved surfaces and I think I’ve cracked it. Here’s a teaser to get you interested: What you see is a sphere rolling on a c…

So glad I left a note for myself from the past. I really want to model the spinning Pringle that can support a ball stably and I wasn't sure if I had the code to do it. arundquist.wordpress.com/2022/12/31/r...

I really love the TE line showing how the energy is just very smoothly decaying

Pi from collisions in a forest Ok, I know I’m a day late, but it took me a while to figure this out. This is a post describing a very dumb way to calculate pi. It was inspired by the awesome explanation of one of the coole…

One day late pi-day post. A very dumb way to calculate pi. It involves bouncing a disk around in a forest (with some traveling salesman thrown in) arundquist.wordpress.com/2025/03/15/p... inspired by @3blue1brown.com and @standupmaths.bsky.social

Can’t Wrap Your Head Around Pi? Here’s a Cool Visual to Help Pi is an irrational number, and like some irrational people it just goes on and on. What is it with this crazy, crucial number?

Ah Pi day. I love it! Here's the first of what I hope to be several great reads (this one from @rhettallain.bsky.social ) www.wired.com/story/cant-w...

loving the @standupmaths.bsky.social @stevemould.bsky.social @3blue1brown.com combo around blocks colliding and pi calculations. Somewhere I've got a notebook looking at collisions between non-infinitely strong materials (so each collision takes a while). I need to dig it back up!

just set it to be above 15kHz so us old people can't hear it

I used to do 4 follow up questions after the class finished a problem on the board that were all very easy to answer if they did it with variables (like "what if the mass doubled?"). I noticed that more people started going to that approach first

Love this. Though I do struggle with the Hamiltonian when teaching CM. My Ss say "so just do the Lagrangian approach and then do some more things just because we can?"

The map of how an observer would calculate the angular momentum of a moving particle looks like the map of the magnetic field of a moving charge. Useful? I've never made use of that in my teaching but my EM intuition is stronger than my angular momentum intuition, I think.