quote:Original post by grhodes_at_work
Do any flying these day? What type of aircraft?

Not for a long time unfortunately.... (that stupid PhD thingymajig)... and I had to let my license lapse when I went back to being a poor student all those years ago. I keep my withdrawal symptoms in check by building and flying R/C gliders and powered aircraft, but it isn''t quite enough. I''m trying to convince my wife to come learn gliding with me, since I''m of the belief that it is the ultimate in flying.

I trained on a Piper Tomahawk and flew that, and a couple of Cessnas (150 and 172 I think they were... but it''s been a long time) for several years. Unfortunately another student put the Tomahawk on its back in a nearby paddock and that substantially cut the flying schools fleet (by 33%)! After that I flew less until eventually I just stopped going (fuel prices got ridiculous).

Today I''m just one of those poor souls who gets that itch every time he gets on a commercial aircraft!



Timkin

Hey a2k, how''s Hecker''s physics code working for you? I''ve been working on a rigid body simulator from his tutorial over the past few weeks, for use in a racing game. Just today I''ve gotten to the point where I can steer my luge/sled-type vehicle through my half-pipe track.

Anyway, remember "Hover", an old project of mine? Didn''t we discuss its physics a long time ago here on GameDev? My vehicles floated on springs, and I thought I''d suggest this to you as a hack to avoid actually doing any multi-point collision resolution. Ever since I worked on Hover, I''ve always thought that a vertical spring would be an easy way to approximate the behavior of a wheel under suspension. You''d still *render* an appropriately-positioned wheel and suspension arm, but these components wouldn''t actually exist as bodies in your simulation.

quote:Original post by a2k
because papers i''ve read on collisions always discuss single point collisions, but not multiple collisions.

Okay, I think we''re finally getting to the heart of understanding the specific problem you are trying to solve.

Let me see if I have this straight.

You know how to implement single point collision detection and collision response, but you''re not sure how to do multiple point detection and response... correct?

Assuming this is correct, there are two ways that I can come up with off the top of my head to deal with this situation.

Consider the bank angle of the aircraft at the point of contact with the ground. If this angle is not zero then one wheel will touch before the other.

Method a) Treat all angles less than epsilon (where epsilon is a small number) to be the same as zero and then treat your main undercarriage as a single contact point.

method b) For angles larger than epsilon, you can deal with the two contacts individually. The first contact will cause the aircraft to rotate onto the other gear since gravity will be countered (at least partially) by an off centre contact force. You then have a rotational dynamics problem to solve, but it shouldn''t be too difficult.

If the pilot is particularly bad and happens to drop the nose wheel onto the ground before getting the aircraft settled on the main gear, then just deal with the same rotational problem as method b). If they happed to ONLY get the nose wheel onto the ground, it''s going to break since they''re most likely flying INTO the ground!

I hope this helps further. If my assumption above is incorrect, could you please elaborate on the particular difficulty you are having.

Cheers,

Timkin