Box2D
A Quick Introduction
Box2D Entities
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Body
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Fixture
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Shape
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Joint
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Contact
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World
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Body
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Fixture
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Shape
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Joint
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Contact
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World
Body
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A point (no size or shape).
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Got Position & Velocity.
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All bodies in Box2D are rigid.
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Can "carry" fixtures.
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3 types of bodies:
- Static
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Dynamic
- kinematic
- Static
- Dynamic
- kinematic
[ Static ] Body
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Has infinite mass
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No Velocity, (position is set by user)
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Does not collide with other static bodies.
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Used as walls, platforms etc...
[ Dynamic ] Body
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Fully simulated - i,e can be moved by force.
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Can collide with all 3 types
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Has a mass (finite)
[ kinematic ] Body
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Hybrid of static & dynamic
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Can have velocity
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No response to forces
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Collide only with dynamic bodies only
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Used for things like moving platforms etc...
Fixture
=
shape + (density, friction, etc...)
Fixture Properties
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Density -> used to compute the mass of the parent body
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Friction -> used to compute friction on contact...
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Restitution -> used to make stuff bounce!
Shapes
- Simple classes to describe collision geometry
- Box2D supports ellipses and convex polygons
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Also "Edge Shape" & "Chain Shape"
Force & Impulse
- b2Body.ApplyImpulse() - Bam! all at once
- b2Body.ApplyForce() - slow
- b2Body.SetLinearVelocity() - ignore simulation
- b2Body.SetLinearDamping() - affects all forces
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b2Body.SetGravityScale() - affects gravity
Collisions!
- Are managed with contacts
Joints
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Distance Joint - keeps constant distance
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Revolute Joint - Rotate around a point
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Prismatic Joint - keeps rotation aligned
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Pulley Joint - 1 up and 1 down
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And a few more...
Using Box2D with QT
Demo
Questions?
Box2D Quick Intro
By Vitali Perchonok
