I was thinking about a force-based rts movement thing the other day. This is how I'd do it, & I'm sure it could efficiently handle movement, collision & pathing for hundreds of units:

I'll keep updating this thread with entries & possibly some base templates (which are a must when working in a short timeframe).

One Hour Game Jam happens every Sat at 20:00 UTC, usually with a stream by Ludum Dare pixelart legend Bitslap (& brothers) afterwards where they laugh at how bug-ridden the entries are: http://onehourgamejam.com/

It's great fun & I'm finding it a useful exercise in focus & productivity (even though I can never finish in the hour), plus some good ideas come out of it. C2 is of course the ideal tool for rapid prototyping, & after recommending it to a few people in the chat I thought I'd post the source of my better entries. I've given them a quick cleanup & added comments about my thought process as well as the code itself.

Platforms of the Dead (theme: Horror)

Playable link: https://dl.dropboxusercontent.com/u/523 ... index.html

Source: https://dl.dropboxusercontent.com/u/523 ... eDead.capx

music from: http://nervoustestpilot.co.uk/album/def ... xe-edition

Shadowlight (theme: Light)

Playable link: https://dl.dropboxusercontent.com/u/523 ... index.html

Source: https://dl.dropboxusercontent.com/u/523 ... light.capx

uses Polygon plugin by Yann: plugin-polygon-update-2013-04-23_t77970?&hilit=polygon

Explodorama (theme: Dynamite)

Playable link: https://dl.dropboxusercontent.com/u/523 ... index.html

Source: https://dl.dropboxusercontent.com/u/523 ... orama.capx

Stealth Chess (theme: Chess)

Playable link: https://dl.dropboxusercontent.com/u/523 ... index.html

Source: https://dl.dropboxusercontent.com/u/523 ... Chess.capx

Moiré (theme: Grids)

Playable link: https://dl.dropboxusercontent.com/u/523 ... index.html

Source: https://dl.dropboxusercontent.com/u/523 ... Moire.capx

Here's an example that might be handy for anyone making a physics platformer using Chipmunk. It's something I made to try out puzzle mechanics & has a few issues, but it might be worth dissecting to see eg. how 1-way collisions are now possible after rojo's update last week:

https://dl.dropboxusercontent.com/u/523 ... pe_v2.capx

EDIT - tweaked movement to be more like the stock platform behavior

Congrats on being in the top 5, well deserved & a really fun game.

R0J0hound

I've been trying to make one-way platforms & saw this: https://chipmunk-physics.net/unityDocs/ ... neway.html

Is this possible to set up with a pre-step event?

jeebroniz

Here's how I would handle rotating to a target angle using torque:

https://dl.dropboxusercontent.com/u/523 ... mping.capx

It uses the same principle as the magnet thing I posted here the other day: apply torque proportional to angle difference of object to target, then add an opposing torque proportional to the object's angular velocity to act as damping.

It'd crude & fairly math-free, but completely force based so won't cause the issues you get when directly setting velocity or position.

Rojo gave a better example here which uses proper torque calcs involving inertia:

viewtopic.php?f=147&t=122190&p=871121&hilit=physics+rotate+towards+angle#p871121

navel35

Rojo's behavior is built on a javascript port of Chipmunk2d 6.1.1 & I think that's unlikely to get updated.

Prominent

Yeah i've been doing that kind of velocity damping. I want to see if a force only approach is possible, to see if that improves collisions.

Here's a comparison of velocity vs force based magnets (very simple with no falloff or damping, just constant velocity & force applied) to show how much better collls are when you don't mess with velocity:

https://dl.dropboxusercontent.com/u/523 ... rison.capx

EDIT: I think i've cracked it - damping force just needs to be a force opposing the object's angle of motion (chipmunk has an expression for that), proportional to its speed. Throw in a multiplier, negate gravity & it seems to be good, perfect collisions.

new capx - https://dl.dropboxusercontent.com/u/523 ... mping.capx

R0J0hound

Prominent

anyone argh

Any idea how to handle damping with a force-based magnet/point attractor so that attracted objects don't overshoot & fly around the centre? I've tried a bunch of expressions where force decreases towards the centre, with an opposing damping force based on velocity, & nothing works.

The current method I'm using sets velocity directly, & it's fine until stuff gets dragged through walls. I'm hoping that forces will solve this, since they're always the recommended way of moving things in physics engines.

https://dl.dropboxusercontent.com/u/523 ... oblem.webm

jeebroniz here's what rojo said about the joint part of your question:

[quote:2o3yi1ny]According to the chipmunk forums the way to join two objects together is with two joints. A pivot and a gear joint. I apologize fo the seeminly complicated formula used for the phase of the gear joint. It's the signed angle difference between the two object angles. angle(0,0,cos(a-b),sin(a-b))

This is the capx he posted:

The easy way to disable collisions between the two objects while still keeping their physics collisions with other objects active is to set their collision group property to the same non-zero value.

R0J0hound there's a minor bug when you try to alter the mass of an object with a polygon collision shape. Not a biggie, the workaround is to set coll shape to box before setting mass, then switching it back to polygon afterwards.

Here's the error message:

Great stuff, fun & very playable. Nice ending & I liked the stats thing at the end (highest combo 19).

Would make a nice little browser or mobile game, & if you do continue it then I think the object spawning on levels 7+ could be tweaked. I had lots of attempts where I'd catch every jumpable object but still die. Maybe have more regular ground vehicles or missiles? Or adjust the random spawning to not be purely random, eg. on a timer with +/- some random number.

maybe you should rename the game to (╯°□°）╯︵ ┻━┻

+1 for the high res, & pm sent