Box2D - Colliding with corners of tiles

[Tatsu]

I've started putting together a simple platform game intended to take advantage of Box2D, but it looks like I've come across a pretty basic obstacle early on.

I'm generating the collision in the world by adding a bunch of tiles placed in the level that have been snapped to a grid. These are added to body 0. A player character (body 1, with rotation disabled) is moved around by applying X force.

Occasionally, while the player body is being pushed along a smooth surface made up of multiple tiles, it will come to an abrupt halt. This only seems to happen the moment the player body crosses over the next tile. My best guess is that it's technically colliding with a side edge of one of the tiles that make up the ground.

Is this a problem anyone else has encountered? What is the best way to reliably move a body smoothly over a series of static boxes?

Thanks!

[LB]

Maybe make the base of the character circular in the phizix world?

[Werbad]

This is actually a very common problem for people who create tile-based games.

The best solution I know of is to merge the tiles along the same surface into a single polygon, but this is unfortunately not always possible nor easily implemented. Another solution is to build the static terrain by tracing the borders with line segments/edge chains.

Making the base of the player a circle works in some cases, but the problem might persist if you have moveable boxes or similar objects where changing the physical shape isn't possible.

Erin Catto, the creator of Box2D, has this problems on his todo-list, so it will probably be fixed in a future version of Box2D, but for now a work-around has to be used instead.

[netninja]

I have run into the same problem as you Tatsu, and yes the only solution that I've found is the one Werbad mentioned, of combining the surface into a single polygon. It makes it a bit hard for tile based games though.

[Fimbul]

Is there an easy way to do this (without having to deal with creating a "box2d map" for every level)?

[Tatsu]

Giving the sprites a circular base is a good workaround for me. It makes the characters slide off the edge of a platform, but I actually like that effect.

Thanks for the advice!