Details of Physics Engine

[mscottveach]

I've been browsing through the forums and read a lot about the combat/physics engine
being planned for the game; it's clear from the videos and statements that it could end
up being pretty incredible.

I'm curious to know more detail though... is there a thread or an interview where they
go into substantially more detail about this engine?

Here are the kinds of things I'm curious about: they say that their body simulation
is built on a muscle/bone simulation. Have they gone into any details... how many muscles
are they modelling? which ones? are they using underlying musculature for *all* actions
or is it more of a hybrid system? is there a list of all the biological systems they're
planning on modelling (respiration, lactic acid, etc)?

I mention those less because they're exactly what I want to know and more as
an illustration of the kind of detail I'm hoping for.

I've been picking up little details as I read through these forums but I thought I would
check to see if I've somehow missed a post, blog entry, interview that really gets into
the nitty-gritty of their design choices in the engine?

I'm also curious as to how well it's working... I know in the past when people have
tried this approach they've been unable to thread the needle between accurate and
entertaining. If we take what they say at face value, how far along is their physics
engine? Do we know?

 

[CJB]

As far I as can tell the alpha version is close to release. Which makes me think that the physics engine is near to complete when it comes to features. The only thing that I am wondering if there are also creatures in game which has more then two legs.

 

[Empire²]

Welcome to the forums!

I think CJB is not too far off, but the alpha is not close to release. Or at least, this has never been said word-for-word by any of the developers as far as I'm aware. All we know is that it's the next thing on the agenda, but we haven't been given an ETA on it yet, and if we have, I doubt it's any time this year.

The core mechanics are the first thing they're trying to get done, before moving on to anything story-related. This includes animation, graphics and yes, the physics engine. While I genuinely adore the physics in SG and in games in general, I can't say I've been on the lookout for any information regarding the exact specifics of the engine. I think 'muscles' are something you shouldn't take too literally. It's generally a term used in animation and game development, and merely means that what drives the directional or rotational force of any given limb. I doubt there are organic 'muscles' in the characters, that work their force on the flesh surrounding them (e.g. flexing your biceps) in the game, and that things like lactic acid will play any real roll. I'm assuming they're technical muscles rather than biological ones, solely for movement and the restriction of, and not something you'd actually physically find in a character when you chop off an arm or something along those lines.

Your muscles' force wears down as your stamina is drains, making your swings slower and thus less powerful. I think the muscle strength is a parameter set within the code that changes dynamically as the state of your stamina does, and that the muscles are neither "physically" changing their behaviour or even there in the first place.

Of course, we'll have to wait for an official response. I'm just saying what I think comes the closest from what I have gathered on Sui Generis and game development in general.

I sincerely hope this is somewhat helpful!

 

[arrob]

since this is an rpg and you dont get to play with the engine while playing normally, its rather unimportant. im pretty sure they will not have a correct physics engine, but do tweak theirs in a way that feels most realistic/natural (i just jope they do have experience in realistic combat and dont refer to other games there, but i fear they do refer to other games).
a real physics engine would mean that you could add any weapon model you think of and it would perfectly work as it does irl without any adjustment. im very sure that (and especially using muscles to walk and stuff) is just too complicated.
im also a great fan of correct physics, but if it atleast feels like its correct, im ok with that. its not good but definitly better than most games out there.

i really like how many people here use animals in austronaut suits as avatar, is there a specific reason?

 

[Empire²]

*snip*
i really like how many people here use animals in austronaut suits as avatar, is there a specific reason?

Yes, they are fantastic. That's the sole reason.

Anyways, I don't entirely agree with you on some of your points. I think, and this may sound a bit harsh, that you haven't really looked into the game too much. I sincerely apologise if that is not true, but you've made various points which sound like you haven't actually seen the game in action. Their physics engine is as "correct" as it gets, especially for an RPG. Weapons, objects and players have accurate and realistic collisions, weights and C.O.G.s (Centre Of Gravity) based on all of their properties, rather than a simplified hitbox and an assigned value. Weight and momentum play a big part in the game, especially the combat, and it's handled in the way it would be in real life.

A real physics engine does not mean it's self-configuring for any possible 3d model you can think of. Every model and asset in game is hand-crafted, and the hitbox for every object is added from that same 3d mesh I would assume. The weight, however, is a different thing. You can't make a 3d model of a sword and expect if to translate into a game. A game cannot recognise materials from something like a general shape. You'd have to, probably in-game or using some sort of utility tool, define the materials and their properties, including weight, texture and many more things.

Almost every game, however, uses animations. Whether they are static (canned) or active (uncanned) is fairly unimportant if you look at it in black & white. Those that don't, however, are often games that don't include any substantial gameplay. Sui Generis makes use of active animations, meaning that any possible interference from terrain or objects within the game affects the animation in some way. If it didn't, for example, your feet would clip through the terrain when walking up and down slopes, because the standard animation is that for walking on a straight surface.

Skyrim has a physics engine too. However, for the most part, it uses static animations. Using two different weapons does not affect your attacking animation, no matter their "weight", as it is defined in The Elder Scrolls. Outside of the game's context, weight is just a utility measurement system for whether or not you are over-encumbered. This, again, is a binary thing. Whether your carrying capacity is 10/100 or 90/100, your animations are not affected. However, it still utilises its physics engine for various things, like the ragdoll physics on dead characters, various forces on objects, like gravity, as well as, like in Sui Generis, the somewhat accurate collision between your feet and the ground.

Bare Mettle have expressed that the object editor will possibly allow you to add your own weapons, armours and various other peripherals into the game. But no game can configure that object for you, because a 3d model doesn't have any weight or balance. That is because a 3d model is not made of wood and steel, but of polygons. Weight, balance, it all needs to be defined by someone in some way, whether it's the devs for an item in the release, or a community member when creating a mod somewhere in the future.

 

[Darkzone]

Is the volume off an object counted out or filled with particles? How does it react to weapons made of two different materials like wood and iron?

 

[arrob]

i did assume that the weapon was made of steel therefore with a continous mass distribution (a wooden hilt is possible but would not have a big effect on most weapons, but youre right this needs to be considered too). a real physics engine would NOT need more information besides this and the model. but there are very important physical properties that you may not think of in the first moment, for example air friction. if you strike with a sword in the air normally, and then turn it by 90 degree and do again youll notice the difference. same of course (or even more) for the comparison with a club. i highly doubt they have correct formula to calculate air resitance. and youre right that i basically guess, youre free to believe otherwise although its unlikely. instead i assume they just tweak some parameters in their engine to make it feel that you have air resistance.

its also a matter of proportionality. combat in this game will be mostly automatically. means you press a button and your character does the rest (as its done in most games, im glad that you have some more possibilities here but you cant disagree with that statement). this results in many aspects being ignored, just look in this topic
http://www.baremettle.com/sg/forums/index.php?threads/some-suggestions-while-the-game-is-still-in-development.1089
and thats why i think they are well served with how they do it. its pointsless pushing for 100% realism on the one side while the possibilities are limited so much that it still does not even barely look/feel like a real fight.

 

[Tessaya]

its also a matter of proportionality. combat in this game will be mostly automatically. combat in this game will be mostly automatically. means you press a button and your character does the rest (as its done in most games, im glad that you have some more possibilities here but you cant disagree with that statement)

Computer interaction as of today is always some sort of "push a button, something happens", but if you expect to win fights in SG with just some light hearted clicks on your mouse, I think you'll be disappointed.

 

[THIEF]

Will it be possible to use your own body to attack? Example: You make a fat character, armed with a tower shield. Tower Shield Fatty charges into his opponent and shield-bashes-- No, cannonballs him! Would that be possible?

 

[Tessaya]

One of the most recent Madoc's post suggested some actions might only be doable by specific body types, that one could very well be one of these.

 

[Mark The Canadian]

Honestly all I want to knoe is if the engine allows items to get stuck in models.

I think it would be awesome to be using an axe and get it stuck in buddy's shield or have it embed itself in the blokes cranium.

 

[Rod_Lightning]

Honestly all I want to knoe is if the engine allows items to get stuck in models.

I think it would be awesome to be using an axe and get it stuck in buddy's shield or have it embed itself in the blokes cranium.

Has been shown in one of the dev videos I believe. I believe it was a poleaxe of sorts getting stuck in a shield?

 

[Empire²]

Has been shown in one of the dev videos I believe. I believe it was a poleaxe of sorts getting stuck in a shield?

Yes, but I believe that had more to do with the blade getting stuck behind it, if we're thinking of the same thing. I'm fairly certain that objects such as axes, spears and not to forget arrows will be able to get stuck in certain materials or objects, like shields.

 

[fluffydino2000]

I'd like to know the specifics of the collision detection. The math behind it, how exactly do you calculate such accurate collisions so quickly?

 

[Madoc]

I'd like to know the specifics of the collision detection. The math behind it, how exactly do you calculate such accurate collisions so quickly?

This is something that has been asked before in a game development forum during the Kickstarter campaign and I declined to reveal it before the game's release. The basic idea behind the method is ultimately quite simple but there's some good optimisations involved to make it fast. One of the more notable aspects of the whole thing is how stable and fluid it all is, you don't really get the violent shaking you often see in real time physics when dealing with difficult collisions.

I've actually done a huge amount of work on the physics / collisions during these months. I've made them stable even in extreme cases (e.g. applying strong forces to a ladder entangled in tree branches) and I've improved accuracy and performance but most importantly I've completely overhauled collision detection to properly account for fast motion. The system now actually tests the paths of entire objects through space against eachother. No matter how small or thin shapes are and how fast they are moving they can't miss eachother and the earliest time/place of collision is detected. The previous system was accurate enough for most things but couldn't always deal with say a small light object being propelled at high speed from a force blast.

It's one of those things that can be quite time consuming to do, makes the physics solid and reliable which is great but most poeple will never be aware of it. I'm sure some people will get it and appreciate it but most won't notice or care and showing it in a compelling way would be difficult.

 

[fluffydino2000]

I can understand that you'd be wary of letting something like that slip. The reason I ask is that as an extra-curricular activity to my A-level computing I've challenged myself to make a general purpose (2d) game development software with Java. The inspiration coming from yoyo games' Game Maker: Studio. Recently I've been trying to puzzle out how I'm going to handle collision and I realised that optimisation of something like that is probably quite difficult considering all the different approaches you can take.

 

[Rod_Lightning]

I've actually done a huge amount of work on the physics / collisions during these months. I've made them stable even in extreme cases (i.e applying strong forces to a ladder entangled in tree branches)

Finger licking good, Madoc. Finger. Licking. Good.

 

[crashingtingler]

The "violent shaking" that occurs in many games instantly breaks immersion for me. The effort you put into details like this is profoundly impressive. best devs ever.

 

[lvk]

If it makes any developer feel any better, I wanted to become a backer when the KS video showed the table with the apple basket on it falling over and then they mentioned they had no hidden collision meshes.

 

[Rob]

The basic idea behind the method is ultimately quite simple but there's some good optimisations involved to make it fast. One of the more notable aspects of the whole thing is how stable and fluid it all is, you don't really get the violent shaking you often see in real time physics when dealing with difficult collisions.

I'll also be quite interested to know exactly what's going on, as and when you're ready to share.

I'm guessing the "violent shaking" is done by avoiding the use of potentially unstable optimisation methods, and avoiding the use of random sampling or simulated annealing to escape local minima.

I'm also guessing that objects have got a way of knowing when they're stuck. And, if they're stuck, they've then got an alternative (cheating) way of getting unstuck, rather than just causing the objects to be stuck or shake violently, etc.

The thing that really made me think this is what's going on is around 0:46-0:48 in the Halberd Combat Test video, when the halberd just magically passed straight through the NPC. I figured that the engine had realised that the halberd had got stuck, and thus had decided to just let the halberd smoothly escape the situation, rather than doing something more irritating. Is that pretty much right @Madoc? Or is there something else going on?