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jjbott / RocketLeagueReplayWeb

Web front end for Rocket League replay parser
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linear velocity scaling #1

Open rustyfausak opened 8 years ago

rustyfausak commented 8 years ago

Hey I'm not sure how to converse with you on this, but this seems to be an OK place. I know this repo doesn't have your latest replay viewer.

Your actor.js ( http://bunkmonkey.com:97/angular/app/Actor.js ) has the magic number 0.111399 used for linear velocity scaling on lines 207-209. Any insight as to how you arrived there?

I've been looking into tweening between frames in order to get more accurate collision data. In order to do this I need to be able to use that linear velocity. In my noodling I've found that the maximum distance a player travels between frames is around 300 units. So that would imply a maximum linear velocity of around ~10000. But the linear velocity replication is frequently above that, commonly in ranges above 10000. We know the default map is around 10000 units long, and it takes a player about 4 seconds to travel that distance at max boosted speed. So that's a max speed of 2500 units/sec, which is about 83 units/frame. Which is still way higher than 300 units/frame but there could be other factors at play for speeds like that.

Anyways I just wanted to open a discussion with you since I don't really know anyone else who is working / has worked on this stuff for Rocket League.

jjbott commented 8 years ago

Oh gosh I never pushed all that code hey. Boop pushed!

That magic number came from taking a random vehicle in a random replay, looking at the positions between two random frames, and seeing what scaling factor would work to make the velocities make sense.

But I never found a good scaling factor that worked in all cases, so I abandoned it (it's commented out). So instead, I manually interpolate between rigid body states.

rustyfausak commented 8 years ago

Yeah I see that you're doing interp by just a percentage between two frame positions. But that doesn't really work for collisions since if things collide between two frames it wouldn't pick it up.

I found that the linear velocity is most likely being scaled by RBSTATE_LINVELSCALE, which looks like it defaults to 10 ( https://wiki.beyondunreal.com/UE3:Actor_structs_(UDK) and http://www.codekisk.com/unreal/ut3/scriptref/engine/actor.html ).

I get more reasonable results by dividing the velocity by 100. It seems mostly linear: default

The colors should correspond to different players. I'm not sure what the four lines mean..