Friction in Box2d

Question

I am using Box2d for a topdown game. The "ground" is a series of tiles, where each tile is a static body with a sensor shape. Can I make friction take effect for this, even though the objects aren't really "colliding" with the ground?

If Box2d won't let me do this, I considered trying to implement my own by detecting what force is currently moving the object, and applying a force opposite to it, but I'm not quite sure how to detect that force.

in game physics programming, forces are generally hard to work with, so developers work with velocities/impulses. As for why, that is a longer story, but you can refer to Erin's GDC talks for that — user3471786, Jun 26 '19 at 02:30

score 7 · Answer 1 · answered Apr 06 '10 at 15:35

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Another way of doing this is to set linearDamping on your body. You could set this differently depending on the tile your object is on.

answered Apr 06 '10 at 15:35

Colin Gislason

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score 1 · Answer 2 · answered May 14 '10 at 15:22

Friction is directed against the velocity of the body, regardless of other forces.

If setting linear damping isn't enough or relying on a property of the b2Body is inappropriate, you can easily compute nonlinear friction forces and call ApplyLinearImpulse() or ApplyLinearForce() every frame.

Query the velocity with b2Body.GetLinearVelocity(), scale (nonlinearly) the result as desired to get the force, and invert the sign of both components.
If you decide to stop the body (when it is slow enough to stick), SetLinearVelocity() does the trick without computations.

score -1 · Accepted Answer · answered Apr 05 '10 at 01:41

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ApplyImpulse() instead of ApplyForce() works much better.

answered Apr 05 '10 at 01:41

Nick Heiner

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Why does `ApplyImpulse()` work better than `ApplyForce()`? – Andres Riofrio May 27 '12 at 03:37

Friction in Box2d

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