Platformer Prototype

[DrLuke]

that's dt for you

[DrLuke]

I added a fixed timestep now. Aka you can't fall through the floor when moving the window anymore.

http://dl.dropbox.com/u/28079852/PlatformerProto14.love

[BlackBulletIV]

I wouldn't use a fixed timestep, it's better to limit how much delta time Box2D gets access to:

Code: Select all

local left = dt
local step = .03

while left > 0 do
  world:update(step)
  left = left - step
end

Another way to fix this problem (by my observations) would be to use Body:setBullet. Set that to true, and Box2D will check for collision in a "real-time" way.

[Lafolie]

I'm curious, does this microstep/window movement phenomena only apply to box2D-style physics? I plan on making a platformer one day and I was wondering if I'd have to take this into account using pseudo physics.

[bartbes]

It depends on your calculations, but most calculations do, in fact, need small timesteps for them to at least look like they're accurate.

So, in general:
The smaller the timestep, the more accurate the result. (in most cases, if you recalculate from the start, this is not the case)

Now, as for why this is, these formulas have been created and verified with dt approaching 0, if that means anything to you.

[DrLuke]

I am not using box2d. I made everything myself!

[BlackBulletIV]

The problem would come from the fact that calculations are done using the delta time. For example:

Code: Select all

body.x = body.x + body.vx * dt

The longer the delta time, the more that it added to the position of the object. Unless setBullet is set to true, Box2D will just move the object by whatever body.vx * dt happens to be without checking whether anything was in between.

I am not using box2d. I made everything myself!

Ah ok, but the same thing still applies. When doing your physical updates, limit the delta time as I showed above.

EDIT: 777 posts!

[bmzz]

when the player stand on ground and i hit right(or left) gently, player will Jitter.

[DrLuke]

when the player stand on ground and i hit right(or left) gently, player will Jitter.

Yeah, that's a problem with the friction, soon to be solved.

[DrLuke]

Fasten your seatbelts and don't let any limbs hang outside of the table's boundaries, I'm presenting you:
Collisions with triangles!

ncSoY.png (30.43 KiB) Viewed 549 times

http://dl.dropbox.com/u/28079852/Collisions16.love