Collision shapes

A collision component can either use several primitive shapes or a single complex shape.

Primitive shapes

The primitive shapes are box, sphere and capsule. You add a primitive shape by right clicking the collision object and selecting Add Shape:

Box shape

A box has a position, rotation and dimensions (width, height and depth):

Sphere shape

A sphere has a position, rotation and diameter:

Capsule shape

A capsule has a position, rotation, diameter and height:

Complex shapes

A complex shape can either be created from a tilemap component or from a convex hull shape.

Tilemap collision shape

Defold includes a feature allowing you to easily generate physics shapes for the tile source used by a tile map. The Tilesource manual explains how to add collision groups to a tile source and assign tiles to collision groups (example).

To add collision to a tile map:

1. Add the tilemap to a game object by right-clicking the game object and selecting Add Component File. Select the tile map file.
2. Add a collision object component to the game object by right-clicking the game object and selecting Add Component ▸ Collision Object.
3. Instead of adding shapes to the component, set the Collision Shape property to the tilemap file.
4. Set up the collision object component Properties as usual.

Convex hull shape

Defold includes a feature allowing you to create a convex hull shape from three or more points. You can use an external tool such as the Defold Polygon Editor or the Physics Body Editor to create a convex hull shape.

1. Create convex hull shape file (file extension .convexshape) using an external editor.
2. Instead of adding shapes to the collision object component, set the Collision Shape property to the convex shape file.

File Format

The convex hull file format uses the same data format as all other Defold files, ie the protobuf text format. A convex hull shape defines the points of the hull in a counter clockwise order. Example:

shape_type: TYPE_HULL
data: 200.000
data: 100.000
data: 0.0
data: 400.000
data: 100.000
data: 0.0
data: 400.000
data: 300.000
data: 0.0
data: 200.000
data: 300.000
data: 0.0

The above example defines the four corners of a rectangle:

 200x300   400x300
    4---------3
    |         |
    |         |
    |         |
    |         |
    1---------2
 200x100   400x100

Scaling collision shapes

The collision object and its shapes inherit the scale of the game object. To disable this behaviour uncheck the Allow Dynamic Transforms checkbox in the Physics section of game.project. Note that only uniform scaling is supported and that the smallest scale value will be used if the scale isn’t uniform.

Resizing collision shapes

The shapes of a collision object can be resized at runtime using physics.set_shape(). Example:

-- set capsule shape data
local capsule_data = {
  type = physics.SHAPE_TYPE_CAPSULE,
  diameter = 10,
  height = 20,
}
physics.set_shape("#collisionobject", "my_capsule_shape", capsule_data)

-- set sphere shape data
local sphere_data = {
  type = physics.SHAPE_TYPE_SPHERE,
  diameter = 10,
}
physics.set_shape("#collisionobject", "my_sphere_shape", sphere_data)

-- set box shape data
local box_data = {
  type = physics.SHAPE_TYPE_BOX,
  dimensions = vmath.vector3(10, 10, 5),
}
physics.set_shape("#collisionobject", "my_box_shape", box_data)

Rotating collision shapes

Rotating collision shapes in 3D physics

Collision shapes in 3D physics can be rotated around all axis.

Rotating collision shapes in 2D physics

Collision shapes in 2D physics can only be rotated around the z-axis. Rotation around the x or y axis will yield incorrect results and should be avoided, even when rotating 180 degrees to essentially flip the shape along the x or y axis. To flip a physics shape it is recommended to use physics.set_hlip(url, flip) and physics.set_vlip(url, flip).