Types.hs

{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE ScopedTypeVariables #-}

module Physics.Contact.Types where

import Control.Lens
import Data.Vector.Unboxed.Deriving

import Physics.Linear

-- | Configuring contact constraint behavior
-- | TODO: does this belong in a different module?
data ContactBehavior =
  ContactBehavior { contactBaumgarte :: !Double
                  -- ^ Bias factor: 0 <= B <= 1, used to feed positional error back into a constraint
                  , contactPenetrationSlop :: !Double
                  -- ^ Amount objects must overlap before they are considered \"touching\"
                  } deriving Show

-- | A contact between two objects - the source of a single set of contact constraints
data Contact' =
  Contact' { _contactEdgeNormal' :: !V2
           -- ^ Unit normal of penetrated edge (or direction toward center of circle)
           , _contactPenetrator' :: !P2
           -- ^ Coordinates of penetrating feature (or the best estimate of point-of-contact)
           , _contactDepth' :: !Double -- ^ Depth of penetration
           } deriving Show

makeLenses ''Contact'
derivingUnbox "Contact'"
  [t| Contact' -> (V2, P2, Double) |]
  [| \Contact'{..} -> (_contactEdgeNormal', _contactPenetrator', _contactDepth') |]
  [| \(n, p, d) -> Contact' n p d |]