Tessera

Jedidiah

@jedidiah.dev

Software developer, dabbler in illustration, photography and animation. Moonlighting as a maker of games. Learning about birds. ⫸ he/him 🌍 Glasgow, Scotland 🔗 https://jedidiah.dev/ 🦣 https://hachyderm.io/@jedidiah

11 Posts145 Follower 637 Folgt

davemakes🔶@mixolumia.com · last yr.

I dug up this very helpful old article on the internet archive that I think explains the problem and solution extremely clearly using the way Quake handles gravity as an illustration web.archive.org/web/20160719...

Doing gravity right

Now you may be thinking: "baah, I know how to do gravity.." but there's a big flaw in the commonly used Euler's method to handle the gravity (or other forces). Even all the Quake games have this problem. Then what is it? If you have more frames per second in Quake, your player will run faster and jump higher. There are some places in Quake where you can't jump high enough if you don't have enough frames per second. Sounds odd, right?

Most of the programmers do the gravity something like this:

velocity = velocity + gravity*delta_time
position = position + velocity*delta_time

The algorithm above is ok but when delta_time changes or delta_time is too high, it causes many unwanted problems. Gravity adding should actually be done like this:

velocity = velocity + gravity*delta_time/2
position = position + velocity*delta_time
velocity = velocity + gravity*delta_time/2

That's it.. but you need proof, right?

Results in practice

Here is a "jumping" parabola with different delta times, using the bad algorithm. The picture on the right corresponds almost exactly to Quake. As you can see, you can't jump in Quake if you have less than 3 fps.

(Illustration showing changes in the arc of a jump depending on framerate)

As delta time (dt) gets higher, the jumping curve gets lower.

Now here are results with the new algorithm:

(Illustration showing the arc of a jump staying the same)

Quite nice, don't you think? Accelerating physics are no longer approximation!

Remember that you should do all the accelerating forces like described above, not just gravity.

Integrating to the same results

The proving of the formula can also be done using integration (of course, because you are calculating areas..)

After integrating you'll get this formula:

pos = pos + 1/2*acc*dt^2 + vel*dt
vel = vel + acc*dt

Note that pos = position, vel = velocity, acc = acceleration and dt = delta_time

And optimizing that formula leads to this:

temp = acc*dt
pos = pos + dt*(vel + temp/2)
vel = vel + temp

This equals to the second formula given at the beginning of this document.

Janet Hill @saskajanet.bsky.social · last yr.

When you've got it 🔥 #birds

Head and shoulders portrait of a pigeon with gorgeous iridescent green and purple neck, and orange eye.

Tom Gauld @tomgauld.bsky.social · last yr.

My cartoon for this week's @newscientist.com

A Caroll diagram consisting of four rectangles arranged in a square.
The Y axis is labelled MOVE and split into FAST and SLOW.
The X axis is labelled THINGS and split into BREAK and FIX

Top left image: (Move Fast and Break Things) Tech Bro
Bottom left image: (Move slow and break things) Runaway Steamroller
Top right image: (Move fast and fix things) Emergency Plumber
Bottom left image: (Move slow and fix things) Grandpa with a toolbox

Nic @tismenic70.bsky.social · last yr.

Hi 👋 Little Nuthatch! I love how it looks like it's wearing a bandit's mask! #birds #photography #wildlifephotography #photographers

Nuthatch eating suet pellets on a mossy wall

@ianballam.bsky.social · last yr.

Some of the Alba Wagtail still in the flock in Whimbrel Field yesterday #LytchettFields #DorsetBirds @harbourbirds.bsky.social

Ditch Skipper ☘️@narrowboatireland.bsky.social · last yr.

Some days you just wanna give up , let everything go and follow the light inside of a red cabbage

Alistair Davidson @moh-kohn.eurosky.social · 2y ago

Anyone looking for a top class web developer? UK based

Jedidiah @jedidiah.dev · 2y ago

I wanted to play a bit more with #WebComponents so I made a web component that renders Conway’s Game of Life in an offscreen canvas. Code: github.com/Jedidiah/gam... Demo: jedidiah.dev/journal/2025...

Screenshot of my game of life component with the basic settings, showing light green cells on a dark green background

Another screenshot of my game of life web component, this one is rainbow coloured and instead of the dead cells being removed on the next frame on this version they are just left and overdrawn

Katharine Hayhoe @katharinehayhoe.com · 2y ago

Your weekend reminder that I have a starter pack entirely full of Katharines* who work on climate * alternate spellings are permitted go.bsky.app/Po82tCi

Post nicht verfügbar.

Jedidiah @jedidiah.dev · 2y ago

`Unable to make progress running work. There are items queued for execution but none of them can be started` I'v never had an error message so closely reflect my own internal state. Time for a coffee!

Sandy Horne @sandyhorne.bsky.social · 3y ago

Another photo from my archives. Banded stilts. They always remind me of ballerinas 🩰

Chris Davison @driseamail.bsky.social · 3y ago

Day 3 of Marvel UK themed Inktober and next up is Shevaun Haldane, Dark Angel, created by Bernie Jaye and Geoff Senior

Jedidiah @jedidiah.dev · 3y ago

#intro Hello 👋 I'm a #contract software developer in Glasgow Scotland, I work mostly in #frontend and #mobile. I have a background in #design and #animation I love learning new things and my current fascination is #birds jedidiah.dev

Long tailed tit looking fabulous on a branch.