Represents a physical body containing user defined data, like a WebGL mesh.

By default bodies don’t move. To change this, use withBehavior.

All bodies start out centered on the origin, use moveTo to set the position.

The supported bodies are:

• block,
• plane,
• sphere,
• cylinder,
• particle.

For complex bodies check compound.

A block is created from elm-geometry Block3d. To create a 1x1x1 cube, centered at the origin of the body, call this:

cubeBody =
    block
        (Block3d.centeredOn
            Frame3d.atOrigin
            ( meters 1, meters 1, meters 1 )
        )
        data

A plane with the normal that points in the direction of the z axis.

A plane is collidable in the direction of the normal. Planes don’t collide with other planes and are always static.

A sphere is created from elm-geometry Sphere3d.

To create a 1 meter radius sphere, that is centered at the origin of the body, call this:

sphereBody =
    sphere
        (Sphere3d.atOrigin (meters 1))
        data

A cylinder is created from elm-geometry Cylinder3d. To create a vertical cylinder, centered at the origin of the body, call this:

cylinderBody =
    cylinder
        (Cylinder3d.centeredOn
            Point3d.origin
            Direction3d.z
            { radius = Length.meter, length = Length.meter }
        )
        data

This cylinder is approximated with a convex polyhedron mesh that has 12 side faces.

For more subdivisions at the cost of worse performance, create a compound body with Shape.cylinder.

A particle is an abstract point that doesn’t have dimensions. Particles don’t collide with each other.

Bodies may have static or dynamic behavior.

Dynamic bodies move and react to forces and collide with other dynamic and static bodies.

Static bodies don’t move and only collide with dynamic bodies.

Change the behavior, e.g. to make a body dynamic:

dynamicBody =
    staticBody
        |> withBehavior (dynamic (Mass.kilograms 5))

Get the position and orientation of the body in the world as Frame3d.

This is useful to transform points and directions between world and body coordinates.

Get the origin point of a body in the world

Get the linear velocity of a body

Get the angular velocity of a body

Get the linear velocity of a point on a body.

This takes into account both linear and angular velocities of the body.

Get the center of mass of a body in the body coordinate system.

Get a mass of a body. Returns Nothing if a body is not dynamic.

Set the position of the body in the world, e.g. to raise a body 5 meters above the origin:

movedBody =
    body
        |> moveTo (Point3d.meters 0 0 5)

Move the body in the world relative to its current position, e.g. to translate a body down by 5 meters:

translatedBody =
    body
        |> translateBy (Vector3d.meters 0 0 -5)

Rotate the body in the world around axis, e.g. to rotate a body 45 degrees around Z axis:

movedBody =
    body
        |> rotateAround Axis3d.z (Angle.degrees 45)

Get user-defined data.

Update user-defined data.

Apply a force in a direction at a point on a body. The force will be applied during one simulation step.

Keep applying the force every simulation step to accelerate.

pushedBox =
    box
        |> applyForce
            (Force.newtons 50)
            Direction3d.positiveY
            pointOnBox

Apply an impulse in a direction at a point on a body. Applying an impulse is the same as applying a force during the interval of time. The changes are applied to velocity and angular velocity of the body.

For example, to hit a billiard ball with a force of 50 newtons, with the duration of the hit 0.005 seconds:

impulse =
    Force.newtons 50
        |> Quantity.times (Duration.seconds 0.005)


hitCueBall =
    cueBall
        |> applyImpulse
            impulse
            Direction3d.positiveY
            hitPoint

Set the material to control friction and bounciness.

Make a compound body from a list of shapes.

For example, the sphere from above can be defined like this:

sphere radius data =
    compound
        [ Shape.sphere
            (Sphere3d.atOrigin (meters 1))
        ]
        data

We only support rigid bodies.

Under the hood, we find the center of mass and the inertia tensor. It is assumed, that the shapes have the same density and do not overlap.

Set linear and angular damping, in order to decrease velocity over time.

These parameters specify the proportion of velocity lost per second.

This may be useful to e.g. simulate the friction of a sphere rolling on the flat surface. The normal friction between these surfaces doesn’t work, because there is just 1 contact point.

Inputs are clamped between 0 and 1, the defaults are 0.01.

Transform a vector using the inverse moment of inertia of a body.

This lets you compute angular acceleration from torque, or angular velocity contribution from impulse.

You’ll most likely need to use Vector3d.unwrap on the result.