Source's Awesome (NEW?) Physics Feature!

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Illuminati

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I tend to type too much, so if you just want the info, go down to ****DISCOVERY**** below. The rest of this is just back-story.

I'm a real fan of the physics made available in the Source engine. Ever since I buddied up with a guy at Havok who let me try out a few of their "super secret :devil: " concepts for the Source physics engine, I've been playing with the physics like crazy.

Well today I booted up HL DM to play around in my own private server to experiment with the hundreds of items featured in DM_overlook.

I decided to stack up some explosive barrels against the combine retaining wall, then pack as much of the physics enabled stuff around them, blow them up, and watch my CPU explode trying to calculate all the trajectories of the different objects.

Here is a pic of about halfway through the stacking process.
Hunk O Junk

After that, I gravgunned the car and dumpster right up against the pile. It was around this point that I noticed something odd. None of the objects were jostling around, floating or hovering in odd ways. When I walked into the pile and bumped against it, it didn't budge, and was solid.

I exploded the barrels with a well-placed magnum shot (could you imagine how much fun satchel charges would be? Someone make them!)

Most of the outer objects flew off, but I noticed a good number of the larger tables, etc, hadn't moved an inch. In an attempt to investigate, I jumped on top of the remaining pile, only to find it was rock-solid! I threw grenades, rockets, even launched the dumpster at it from close range. It didn't budge. I was able to climb all over the structure without my weight causing any of them to move or jostle at all.

Then, I took the manipulator gun out and tried to pick up a cabinet that was wedged in tight. It didn't move either. These objects had become a solid mass that no longer reacted to physics! Now at first, I thought that Valve, perhaps had written in coding that would turn off physics for a certain number of physics-enabled brushes that were touching each other at the same time. This would be a smart move to save CPU power.

Then I booted up the console and lo and behold:

*****DISCOVERY******

The brushes had not suddenly lost their physics-enabled status, rather, they had become dependant on the other objects they were resting on or under. The top items could be removed with the manipulator, but they could also be stepped on without that strange "tipping" sensation.

The processes in the console told the story:
Essentially this feature is a structure-building aspect to the coding. It allows a stable (extremely stable) structure to be created out of individual, physics enabled objects. These structures can be dissassembled, but only in a realistic manner, in which objects are only removed from the top down. Untill they are "freed" this 'stasis' one by one by the gravity gun, the objects function as one immovable entity.

This melding stasis is initated by a specific script apparently, and theoretically should be able to be enabled and disabled via console.

The implications of this script (which I have not heard mentioned yet) are far-reaching, especially in the multiplayer mode. A large structure fashioned by players working together on the same team could serve as a bridge critical to reaching a mission objective. This script is special in this case, because as anyone who has stacked brushes in singleplayer to reach out-of-the-way areas knows, they are very unstable normally, and it is easy to destabilize an object stacked upon another object simply by walking or jumping on it if you don't do it just right.

What I do not know about this script is EXACTLY what triggers the "stability script" to engage a series of objects. I do know that stacking an extremely large number of heavy, non destructable brushes together creates the effect. I do not know if it is simply the number of objects stacked or the collective weight of the brushes touching each other that causes the script to engage.

I would really appreciate some of the more code-savy users out there to attempt to re-create this phenomenon while monitoring the console and other physics statistics.

If you do attempt to re-create what I have done in the above screenshot, you will notice at a certain point objects launched via gravity gun into the pile no-longer bounce off as they would a wall or another group of brushes like barrels. Instead, they seem to impact and "lock" into the mass, almost as though the stack had become magnetic.

I would be more than willing to create a demo of this phenomenon if someone could direct me to a link explaining how to record a demo, where the demo is saved, and how to export the demo to another user.

P.S. I know I can be long winded, sorry about that, but I hate posting to forums and getting replies from people who didn't understand what I said. For example:

Dude, you're an idiot, of course you can stack things in this game! Duh!

Anyway, if any of you do understand the script and are able to re-create it as I have done or in any other way, please let me know. I'd also kinda like to hear what you guys think some of the possibilities of this aspect of the physics engine could produce in mod form or otherwise.

Thanks for reading.
 
If what you said is accurate that is an amazing feature, Il mess around with it today and see what I can find out.
 
If this can be implemented in Co-Op mods, could be plenty of fun. As you said, it'd be pretty interesting if a team had to assemble a bridge out of various components while under fire. :)
 
excellent post old chap, i agree entirely and i look forward to mods which involve possibly teams building enitre structures using the physics engine.
 
Very interesting! Illuminati, does it seem tied into collision response? Can you still walk on all the objects normally, it's just that after the 'glue' effect they don't implement 'tipping'? What about with light objects + one heavy one (eg. does the system become a rigid body and take on the inertia of all the objects combined?). I'll have to play with this if I get time.
 
wow, thats realy interesting. thanks for posting it, youve inspired me to mahe a big pile of junk and jump on it / blow it up!!1
 
Dude, you're an idiot, of course you can stack things in this game! Duh!


J/K

=) Awesome find! THX!
 
GREAT FIND! :D

And it works, i just tried it in HL2 SP with cars and other stuff and made a video. Ill go and compress it but ill need a place to host it, any ideas?
 
that's a great discovery

but all you people talking about building stuff under fire? don't think that'd be a whole lot of fun.
 
If I understand your post correctly, I noticed the same effect in the SP with a big (waist-high) pile of weapons, created by typing impulse 101 a bunch of times at the point where you get the blue grav gun (I'd spoiler that, but it has been in about two thread titles a day since the game came out). I couldn't blow the pile apart with grenades, they just stuck to it, and popped the top weapon off when they exploded. I could pull a top weapon off with the grav gun, but not one rom the bottom. It was interesting. This was the afternoon before the HL2DM was released, by the way.
 
Ok, I've played around and made a demo of the effect. I'm quite sure it's intentional, however it isn't PERFECT, as sometimes brushes launched into the pile from the side will SLIGHTLY imbed themselves (this does not occur if you do not launch but rather push or toss).
The demo is 500K, can anyone host it for me?
 
great find and gives modders some great ideas. I'm going to look into it as well tonight. Anyone else on the forum modding? Lets see what observations we can all come up with and find the source code for that so we can predict when that will happen.

Good lookin out bro! Keep it up!
 
I experienced it before. I was playing a map you can download form hl2world (barrel something). There is a switch there that spawn barrels on top of your buggy. I spawned about 50 of them and they really act as if they were making it's own gravity field. Some of them wouldn't even move and when I jumped on them I could hardly jump off. When I did I lost part of my health even though I jumped from like 1 meter above the ground (!) It's strange and fascinating at the same time :]
 
Well originally there was supposed to be a welding feature in the game. Maybe Valve left some of those triggers in the game so that inquisitive players would discover it like they did the first incarnation of deathmatch and coop.
 
I know exactley what hes going on about,, in the leak it must of been enabled... as a certain number of stacked objects welded themselves together... thought it was a bug.. but guess it was a core feature of programming.
 
I'm curious as to why this thread hasn't been pinned. This is a great discovery.

I'm also pleased to see that you have an interest in the Illuminati, as do I.

Anyway, I will be playing around with this a little bit later and I have a rather n00bish question.

Is there any way to convert .dem files to .avi or .mpg files that anyone can view?
 
Cool, so we can build a bridge out of toilets and radiators? :D
 
carefull when climbing on the piles when they get sticky.. i took a wrong step (or jump, rather) and i guess my foot got stuck or something cause i died instantly... I also crushed myself with the buggy when i was trying to zap it up to the top of my pile. :laugh:
 
It's more of a bug/engine limitation than a feature.
 
once again i donno if anyone mentioned this..but ill say it anyways

there isnt a script hat turns on "stability" or whatever u said..i forgot :rolling:

Every object in source has a mass...so if you put a book under 5 barrels..ur not gonna be able to budge that book, because it's too heavy...however u can take off the barrels easier and easier if you go higher and higher, obviously. Source was inteded to make things realistic..if you had book shelf under a tractor, would u be able to move the book shelf? I think not. Just a little opinion of mine.
 
The illuminati??? WHERE! Omfg we're all gonna die!!!! *jumps out window
 
Might be some experiment for some future DM gameplay type.. cant wait to see how valve will exapnd hl2DM, EXITING TIMES INDEED EXITING TIMES!!!
 
After a full day's worth of experimenting and checking script readouts, I'm not entirely convinced it was an intentional scripting, per se.

My honest opinion? I think Valve decided to create a certain "number" where a group of objects stacked OR leaning on each other would give up their constant sapping of the processor (calculating friction vs. mass, etc...) in order to make for smoother gameplay.

However, the fact that objects not underneath other objects can be re-manipulated with the gravity gun is suspicous. Regardless, this knowledge, and the nearly infinite liberty given to us by Valve to tweak their Source engine will mean that with a minor amount of effor this bug/script/limit will mean nearly endless possibilities for modders wishing to take the incredible physics of the Source engines to a new level, perhaps even one that Valve had not originally planned on.

Personally, I find these possibilities to be intriguing.

BTW, it's good to see another interested person in the Illuminati, MGSRevolver.
 
How about having levels that are constructed out of actual bricks !! maybe the engine will make the downward force stable but a sideways force not

Blow holes in walls, etc :D

-QG
 
Amazing find! I like that a lot. Whether its a feature or not; I am sure there are going to be some great new uses for this in the near future....

I may sound stupid and/or ignorant but could someone plz tell me what Illuminati is??

Cheers

=[GcC]= Sir Fragwell
 
I found this as well, I thought it was a bug or some sort of failsafe in case there was too much physics calculation for the CPU to handle.
First thing I did in dm_overwatch was to build a barricade by a lotta stuff and ram it with the two cars. It was fun, so I gathered all the stuff I could find and put them together. I got kinda disappointed when I couldn't ram my massive barricade with the two cars because they had become solid rock.
 
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