Portal’s physics engine rebuilt in 25KB—on a graphing calculator

http://arstechnica.com/gadgets/2012/12/portals-physics-engine-rebuilt-in-50kb-on-a-graphing-calculator/

by username3 • 14 years ago

220 49 14 years ago

Jach2• 14 years ago

Not quite--this is more a recreation of the Flash Portal clone. i.e. it's all 2D graphics and 2D physics.

I got my hopes up for a moment, preparing to be awestruck. Since I have a TI-89, that's what I think of when I hear "graphing calculator". My TI-89 can do 3D stuff (for instance this fun maze generator game http://www.ticalc.org/pub/89/asm/games/amaz89.zip), it would blow my mind to have anything close to a Portal 3D engine on it.

It's still awesome but not as mindblowing as the title suggests...

tertet2• 14 years ago

It would not be that hard to write a 3D physics engine for a TI-89 calculator (Assuming you already know how to write a 3D physics engine, which I do). Problem is, it would be useless since it will probably take tens of seconds (if not more) to calculate each frame.

jlgreco6• 14 years ago

I would not be so sure. It really all depends on how much physics you want your "physics engine" to have. Rag-dolls? Not likely. Quake 1? Sure, you could do physics to that extent on an 89. The 89's are more powerful than you may suspect, unlike the 84 (seen in the article), they have Motorola 68k's.

Here is an idea of what you can do with a 84's Zilog z80 (warning: long animated gif): http://benryves.com/images/nostromo/bsp/2010.11.28/Walkthrou...

(corresponding blog entry: http://benryves.com/journal/3739423)

You can get a lot more out of an M68k. (Actually, to be fair, the M68k calculators' larger screen size works against them, but if you are willing to sacrifice graphics you can easily surpass that demo.)

Jach2• 14 years ago

That's the thing, though. I'd be awestruck to see a Portal 3D physics-like thing on the 89 and be playable, because I'd have no idea how the person pulled it off and as I said above it'd be mindblowing. If you're familiar with physics engines, perhaps you're familiar with how the GBA works at the hardware level and how a game for it is typically made? Super Monkey Ball Jr. is an example of a game that blew me away and I'm still not really sure how they pulled it off.

zephjc• 14 years ago

Technically, that's a raycasting engine (a la Doom and Wolf3D). The first implementation that I know of that was made into a game was Daedalus for the TI-85, back in 1997 http://www.ticalc.org/archives/files/fileinfo/11/1147.html

lloeki• 14 years ago

You ain't done nothing till you coded a 3d engine on a HP48 GX: 131x64 pixels and a 4-bit Saturn CPU. The timing tricks to extort four shades of gray from the monochrome screen were awesome.

http://en.wikipedia.org/wiki/Saturn_(microprocessor)

jiggy2011• 14 years ago

This looks more like a standard 2d platformer.

stickdick• 14 years ago

Not quite...

senorcastro• 14 years ago

The graphics are terrible.

jlgreco6• 14 years ago

It's a 96x64 B/W screen.

JackWebbHeller• 14 years ago

I think that's the joke...

oellegaard• 14 years ago

Awesome! Too bad I gave my TI84 to some girl, after leaving college :(

ionforce3• 14 years ago

That is an excessively sensationalist headline. Portal, physics and graphics-wise, does way more than that graphing calculator.

To imply that they are equivalent is shameful and ignorant.

vacri3• 14 years ago

I don't see any claims of recreating Portal's graphics. I think yours is an excessively sensationalist criticism.

peterhajas• 14 years ago

Claiming to recreate the physics engine implies that somebody remade the Source engine on a calculator. This is a massive exaggeration.

ionforce3• 14 years ago

You're right in a way. Portal could be thought of as two parts, the raw physics and the raw graphics. But when a lay person makes claims of recreating Portal's secret sauce, they're really implying the portal mechanism which is one part physical and one part graphical.

Literally recreating only the physics portion of Portal would be silly.

And yes I was intentionally trying to be sensationalist back because it's a waste of time being victim to submitter's sensationalist headlines, especially on a technical site such as as this (one would hope).

NanoWar2• 14 years ago

Wow that is so awesome. It's running on 6Mhz after all!

rheide• 14 years ago

It's an awesome achievement, worthy of geek praise. But even if I'm being very generous I wouldn't call this a physics engine.

NanoWar2• 14 years ago

There is however another approach by the same guy. Called Zedd Physics Library: http://www.ticalc.org/archives/files/fileinfo/441/44185.html

geori2• 14 years ago

The memory limitations are a bitch. It isn't that difficult to build your engine in that amount of space, but storing any decent graphics or level maps are nigh impossible. I had to quit working on a Zelda clone and JRPG because of memory issues. To this day, I've only seen one long game actually worth a crap and that's Joltima - http://www.ticalc.org/archives/files/fileinfo/34/3456.html Karneges had to use every trick in the book (huffman compression on 4 bit tilemaps) to fit it into 32K of RAM.

Still, it's impressive to do anything like Portal on the calculator. Glad that someone picked it up, even if the headlines are sensational.

loeg• 14 years ago

You can absolutely page in data from Flash memory as needed, it's just non-trivial (and not handled by the "OS"). On devices with flash memory as an extension of RAM (TI 83+, 89, and 89 titanium), this could help for read-only level data that isn't needed all of the time.

Edit: Of course, Joltima targets the TI-83 (different from the 83+), which doesn't have any flash memory. Bravo, Justin Karneges.

jlgreco6• 14 years ago

You can also go the "App" route and make the whole thing an application that runs straight from flash.

Advantages are you can use many flash pages so your application can be massive, and your program will be easier to launch/distribute. We have the App signing keys so these days this route is pretty simple.

On the other hand you have to "allocate" ram to write to or scrounge for ram in predetermined areas in the address space. With regular assembly programs you can have "static" allocations that you can write to. Also programs don't take up a minimum of a single page, so they are generally preferred by people who are more comfortable with their calculator.

Damn, now I really want to revisit that z80 scheme implementation I was working on a few years ago...

fatjokes• 14 years ago

> While programming for graphing calculators admittedly doesn’t give Marcolina’s work a wide reach

Are they joking? Those TI 83's will be used by high school students in the US/Canada as long as TI has this chokehold on schools. They've outlasted god-knows how many versions of Mac's, PC's, Nintendos, Xboxes, PS's.

Evbn3• 14 years ago

How is the TI-83 still a thing? iPod is superior in every way: CPU display size and color, flexibility, cost (well, if they produced a last-gen version for the down market, it would be)

Scaevolus• 14 years ago

You can't lock down an iPod or wipe its memory before a test.

bcoates• 14 years ago

Battery life. Durability.

Also, don't underestimate the value of a UI and hardware keyboard centered around a specific workflow. Calculators are almost the opposite of a tablet/phone, computers specialized to programming and user input, with communication and content consumption as an afterthought at most.

TommyDANGerous• 14 years ago

Watching that demo on the calculator makes me want to play Portal.

yozmsn3• 14 years ago

Oh how I wish I still had a usb-TI83 cable, still have the calculator just not the cord to plug it into my computer...

ygra2• 14 years ago

This one? http://www.amazon.com/☺/dp/B00006BXBS

andrewcooke• 14 years ago

ok, i have to ask - how do you get smiley-face amazon urls?

[update: huh, so it can be arbitrary text. what's it for?]

yozmsn3• 14 years ago

Yes, only I'm not spending $20 to play portal on a calculator...

Evbn3• 14 years ago

More like Portal: Flash Version 2D

http://portal.wecreatestuff.com/

Weird that this portal-dedicated person and Are Technica hadn't heard of Portal 2D.

meaty• 14 years ago

I have doom on my TI Nspire CAS :) Unfortunately the crappy screen is no good for playing it.

I've seen all sorts of hacks like this over the years but to be honest, I've fallen in love with the HP50g for hackability. The thing is awesome.

Not sure if its just me but I seem to accumulate calculators.

hnruss• 14 years ago

TI-83+ was my only hand-held programming system. In high school, I wrote Blackjack, Trapshoot, and a Whac-a-mole clone on it, along with a few originals. I hope that touchdevelop takes off-- it might be the only reason I'd get a tablet.

Portal’s physics engine rebuilt in 25KB—on a graphing calculator

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