Lemming77's Blog

Suspension Diagrams - Workings

2011-10-22T18:45:00.000-07:00

I'm gonna discuss how my Suspension Diagram program works in this post. Brace yourself for maths!

First, I think it should be made clear that this application uses Vector mathematics, much like it's used in video games and graphics software. I haven't used any third party libraries for this, and have simply included the structures as classes in the program, in the interest of keeping it down to a single portable application file with as few external dependencies as possible. Primarily for personal reasons. I stay up late at night so I can hate bloated software more.

I've found two formulas for working out the ratio between spring rates and wheel rates, and I'd wager there's more than those two knocking around aswell. The first I know of is this one, from Autonest. And the other, which I elected to use in this program, I found in a book. Chassis Engineering by Herb Adams, page 26. The formula is as follows.

A: Distance from control arm inner control arm pivots to the center point where the spring acts on the lower arm.
B: The length of the lower control arm from the ball joint to the inner pivots.
C: The distance from the lower ball joint to the suspension instant center
D: The distance from the center of the tire contact patch to the front suspension instant center.

This did require that the suspension in the car be simplified down to just one control arm, effectively turning it into a MacPherson Strut design. This feels like a massive simplification to me, but I figured that won't matter too much in this context. This is simply done by taking the average of all the rod attachments to the spindle, and again for all the attachments to the body, and forming a vector out of these. This formed my control arm for the purpose of the above formula.

The control arm's inner pivot becomes where my control arm attaches to the body, and the ball joint became where this control arm attached to the spindle. A is found by using the dot product of the pushrod's spindle attachment and my control arm vector.

This formula with the variables filled in can be seen on the output images at the time of writing. I'll most likely remove this when I release it, however it can be seen on the images in the previous post.

Now there's only one more thing left in the procedure. I take the Pushrod vector, normalize it, and multiply the output by the vertical component of this vector. I felt that this very easily describes the cosine of the angle between the pushrod vector and the direction of travel. That's what the final number is in the images in the previous post is too. I multiply these two numbers together, and I have the final product.

There's a lot which isn't taken into account. I don't think this method provides 100% accurate results, but at the same time, I don't think 100% accuracy is a realistic target. Not only do setup changes in the ride height and track bar affect the outcome, but so does suspension travel caused by bumps, downforce, body roll, road camber, etc. when out on track. But even this rough figure should help understanding and controlling the handling characteristics of the car.

If you've got any suggestions on ways to improve this procedure, please let me know. :)

Suspension diagrams

2011-10-22T17:49:00.000-07:00

In my venture to learn more about vehicle dynamics, and apply that knowledge to racing simulators, I found the need for some fairly intimate analysis of the cars. The characteristics of the suspension are affected by a lot of things. For instance, in an Endurance Series DBR9, the default front spring rate of 245n/mm translates to a 'wheel rate' of 133n/mm when measured at the wheel. This is due to various factors in the suspension geometry. I figured this would be helpful to understand on a car-by-car basis, so I'm working on a program to draw diagrams of the suspension geometry on these cars. Read on for more info.
If you've studied chassis design, you've probably come across this before. For a start, the force which is exerted onto your suspension by your spring and/or damper is directly proportional to the cosine of the angle between the spring/damper and the direction of travel. And on top of that, there's the effect of leverage to take into account aswell. In fact, theoretically, even body roll can change the wheel rate. But I don't think it's practical to take that into account unless I were trying to simulate the car's behavior.

It's a very straight forward program to use. All you have to do is point it in the direction of a .hdv file, and it produces two PNG graphics showing diagrams of the car's suspension geometry. One for the front, and one for the rear. Here's what the product looks like for the DBR9 in the Endurance Series mod for rFactor.

The green lines indicate the suspension 'bars', the blue line is the spring+shock absorber, and the red dots represent bodies. Typically the spindle and wheel in each corner. A very crude tire is also drawn, so you can see how the tires compare. Both the width and radius are accurate.

Most of the numbers can be disregarded. The only one you really need to take note of is the last one on each side, as this is the ratio between spring rate and wheel rate. The rest is simply there for 'debugging, to ensure the calculations are working properly. I'll go into more detail about the workings and exact calculations in another post.

Currently, the program is able to parse vehicles in GTR2, rFactor, and Race 07 (assuming they aren't encrypted). Adding support for other G-Motor based games like GTL, GSC, etc. shouldn't be a problem. Right now, it doesn't take into account setup information either. But this isn't a problem on any cars without adjustable track bars. I'm still ironing out a lot of problems in it, but I intend to release it once I have it in a state I'm happy with.

Alien Swarm & Formations

2010-07-22T02:53:00.001-07:00

I think I've been playing too much Alien Swarm. Since it's release 2-3 days ago, I've got 22 hours of gameplay, according to Steam. Doing my best to get all the achievements. Note the progress through the campaign on insane difficulty, which has proven to be the most enjoyable thing I've done in the game so far. It certainly isn't easy though, we've had to be really strict with our strategies. Which hopefully will help anyone else who's trying to do the same thing.

The best thing you can do as a team is be coordinated. Communication and organisation is key to success. You'll have to be strict, but it makes such a big difference, you won't regret it.

First of all, weapons. The tesla cannon is great for clumsy team members, as it's impossible to waste ammo with it, and it won't hurt team mates. In fact, I'd generally recommend it for anyone doing almost anything apart from crowd control or burning biomass.

The most harmful thing in the game is any enemy someone doesn't notice. If they sneak up to your team via a blind spot, then they can start attacking, and there's a good chance team mates reacting will hit the alien's victim too. So this is exactly what we want to avoid. And we can do that by simply having the team stay in formation.

Formation

The easiest way to organise the team is to establish formations and stick to them. Everyone knows where they should be relative to their team mates, and from there can pretty much look after their own firing line.

1 is the pointman, and should carry a heavy weapon (minigun, autogun, etc.) to dive head first into whatever trouble you're approaching. 2 and 3 should have medium weapons (assault rifle, shotgun, PDWs, tesla cannon) to cover the sides, and 4 cover the rear with a medium weapon too.

In the event that one person can't handle what comes their way, then the two closest team mates can turn and give some support, adjusting their position if necessary to keep their team mates out of their firing line. However the person on the opposite side to this should NOT turn around and shoot, or else risk friendly fire and enemies sneaking up on them.

Bear in mind you can and should turn the entire team, so you always have your point man facing in the direction you're moving.

For longer maps (such as residential area), a dedicated medic (healing beacons + healing gun) might be required, who will not be able to shoot any enemies. Therefore it would be a waste of time to put the medic on one of those four corners. Instead, there is a triangular formation you should adopt instead.

A flat side of this triangle should take point, focusing more fire on where you're headed, and one focused on the pile of bodies you just killed. If you're fleeing from a large amount of enemies, then this formation can be easily turned around.

With the medic placed firmly in the middle, he can heal all his team mates without trouble too. And of course, redirect fire as necessary.

This is a great formation if one person dies, or you only started with a three man team aswell, if you disregard the medic in the middle. If in a four man team with a dedicated medic and the medic dies however, chances are you're fucked. You only ever have a dedicated medic because you need one.

In tight spaces, these formations can be difficult to maintain. So the best thing you can do is have someone covering the front, someone covering the rear, and just move in single file.

If you happen to run into any trouble, just stop, and adopt this 'staggered' formation. This'll enable two people to fire in each direction. This formation is more difficult to hold however, and more prone to friendly fire. Don't move unless you absolutely have to, and if you do, hold shift to move slower.

Breaking formation

There will be occassions when you need to break the formation though, such as when you meet a shield bug. Just surround them, and attack from multiple directions. If possible, freeze/stun it. Once it's dead, get straight back into formation. It's the same sort of thing if there's more than one, you just have to make sure the team's in good communcation, and always knows which target to focus on.

Sad panda's shield legs don't work when sad panda's flanked.

If a spitter spits at you, don't be afraid to break the formation by rolling. It takes less than a second to get back into formation. You'll have plenty of time to kill the spitter, and you'll save yourself some health.

Splitting the team

This is usually a really shit idea. As how much resistance you meet doesn't vary based on how many of you there are. It's a high risk strategy only worth using in speed runs, so I'll go ahead and quickly go over it. I'm also going to assume you want to split up because you are doing a speed run.

Plan ahead when you want to split up. Because any confusion when you get to a junction and just shout "split up, guys!", you could easily have 3 people go one way and 1 go the other. This can lead to one or both of two things; A) The guy on his own will die, or B) You'll lose time correcting the mistake.

Establish who's going where when you split the team while you're in the lobby. If you do this and your team doesn't consist of fucking idiots, you'll be fine.

Parasites

Parasites hurt. A lot. If someone is infested by one or more parasites, they're dead unless a medic can get to them. Flame throwers are a good defense against them, and medics are a must have in case the flame throws don't work. If you have electric armor, a shock from that will do a lot of damage to the parasite, and could easily save your life.

Depending on the team's exposure to parasites, it might be worth bringing a dedicated medic. This is certainly the case on the Residential Area level. Protect the medic, ensure there's somebody armed between him and every alien in the area. Although he can save your life if you end up infested, he can't do it many times. Infestations are a huge drain on healing supplies.

A particularely brutal last resort if there's no chance you can heal is to run somewhere far away from your team where they won't be going before they kill you. If a parasite kills someone, that parasite will duplicate several times. And a bunch more parasites is the last thing you want near your team.

Dealing with parasites in tight spaces isn't much more difficult, however. Put the medic behind your point man, and he can provide healing to the one most likely to become infested.

There's also good formations to take when backed up against a wall or in a corner, which don't take any explaining. The same principals apply; make sure you can shoot in every possible direction, and make sure your medic can heal anyone if you've got one.

Good luck. You're gonna need it if you're playing on insane. If you're on easy or normal, then you really don't need to worry about formations. You'd also be a great big wuss. Grow some guts you sissy.

Also Blogspot needs more 'read more' buttons.

Project Lemon update

2009-04-11T00:57:00.001-07:00

Yes, I know, at fucking last, what took me so long, leave me alone >:(

Anyway, this update just rounds off a few of the rough edges. Hopefully after this I can leave it alone. Maybe I'll pick it up again in a while, maybe I'll never touch it again. Either way, here it is for anyone who wants to to check it out, pick bits out, expand on it, whatever you want. Enjoy :3

Changes being new, more high-resolution skin for the enemy soldiers; 2048x2048, mainly just more detailed clothing. The rest hasn't changed. Wouldn't need to have gone to this extreme had detail textures just fucking worked on models... :/

I've also made some adjustment to the weapons I've forgotten about, fixed the bone merge error (thanks Vet), and sorted the "switching sides twice" issue with the camera.

Project Lemon Release 2

2009-03-07T10:55:00.000-08:00

Progress has gone nicely on version 2. I've adjusted the weapons to make them more accurate, fixed being able to change the camera to the same side over and over, got some model fixes from Ken to include, and it's actually independent from CSS now. I'll release it when I get those models from Ken, and after that hopefully get away with never touching it again. :D No real ETA though, sorry, I keep forgetting to ask him for them... :(

Project Lemon Release

2009-02-06T21:26:00.001-08:00

And it's about fucking time too, don't you think? Only took two long years, and still it's full of bugs and stuff. Well... Enjoy. :)

I've got the urge to write a novel about this, just because I can, so for anyone who can't be assed reading the rest; video aaaaand download

Difficulty can be adjusted using three configs as well as the options menu; skill_wuss, skill_usual and skill_onemanarmy. skill_usual will be used by default every time the game starts.

It does require that you have CSS installed to run it at the moment, and although I haven't tried it, I'm sure it'd work fine without. Just comment it out in scripts/addcontents.txt if you don't have it. No promises though! Like I said, I haven't tried it.

The only level I've provided is Kielbasa's masterpiece smod_drainage, released without permission (sorry D:). Anything else you'll just have to add yourself. If anyone puts together some mapadds they feel work well in this, please do share. I'd love to see. :3

It's come a long way. It started as basically an undistinguished weapon/skin pack using every feature it possibly could in Smod.

After some time, I decided it sucked ass, was as good as a tactical clone, and needed some twist to it. That twist ended up being a third person camera, similar to that seen in Gears of War. I know Tactical has the same thing, but I did it first damnit! >:( Ken, back me up here :P

It evolved further, however I grew very fond of the camera stuff I'd come up with, so ended up concentrating on that mainly.

Not much has changed since the video on Youtube I posted a while back, so I guess that serves as the best taste of it you're gonna get before playing it.

I had one friend who told me while I was working on this that he didn't enjoy using third person cameras. He wrote this in a comment on the video too, which... Apparently wasn't particularly well received... But thinking this was a terrible shame, I did include a very basic first person camera. By this time I'd put zero effort into view models though, so he'll just have to make do with cam_attacheyes. F2 to enable first person, F3 to switch back to third. Enjoy Eb, yiff in hell furfag. :3

k I'm done rambling. Enjoy.

Moar smod

2008-12-08T10:05:00.000-08:00

So yeah, my obsession with Smod carries on. Lemon remains my on-again-off-again project, as it has for the past year and a half, so I estimate it'll be released some time late '09 lol

That's not all I've been doing though. Got a bunch of other custom weapons working right now. First up, an M4. Four versions of it, one vanilla, one with an acog, one with a suppressor, one with both acog and suppressor. Custom sounds, working world model, no ironsights besides on the acogs because they're meant to fit into HL2.

One Two
Next up, BRII. Two versions, vanilla and scope. Uses that fancy subviewcam stuff. Huge thanks to veteran_gamer for helping me get that working. Most bizarre solution ever. :D

One Two
Next up, one I like to call "THE RAEP SHOTGUN", or pwnzerfaust for anyone seeking a more tasteful name. It's a lot of fun... Watch this! *BOOMBOOMBOOMBOOMBOOMBOOMBOOMBOOMBOOMBOOMBOOMBOOM* Did you see that? No, of course not, because the instant it started firing, everything was swallowed by a BIG FIREY CLOUD OF DEATH!

One Two Three
And last, a work in progress... One for any No Country for Old Men fans, the only one without a working world model, casings ejecting, etc. (but that stuff's coming soon)... Shotgun inspired by the one Anton Chigur uses.

pic4u
Also, anyone who wants to complain about the ironsights, incorrect mirroring, etc. can shove their suggestions up their ass 'cause I'm not interested. *glares at Smod Tactical forum*

I really should do some work on Wipeout... The track's what's got me stuck right now. Also, Twitchy licked me. Is this some Furry gesture I don't know about? Or a sign that he's gonna rape me? Also, I still miss Ken. :(

I miss Ken and Warman...

2008-10-27T20:04:00.001-07:00

Project Lemon

2008-10-08T21:04:00.000-07:00

Yeah, it's a video.