mirror of
https://gitlab.com/sheaf/metabrush.git
synced 2024-11-23 15:34:06 +00:00
compute roots of envelope equation
This commit is contained in:
sheaf
parent
df2469487d
commit
7431e8ba67
|
|
@ -83,6 +83,7 @@ library
|
|||
exposed-modules:
|
||||
Math.Bezier.Cubic
|
||||
, Math.Bezier.Cubic.Fit
|
||||
, Math.Bezier.Envelope
|
||||
, Math.Bezier.Quadratic
|
||||
, Math.Bezier.Spline
|
||||
, Math.Bezier.Stroke
|
||||
|
|
|
|||
455
src/lib/Math/Bezier/Envelope.hs
Normal file
455
src/lib/Math/Bezier/Envelope.hs
Normal file
|
|
@ -0,0 +1,455 @@
|
|||
{-# LANGUAGE ScopedTypeVariables #-}
|
||||
{-# LANGUAGE TypeApplications #-}
|
||||
|
||||
module Math.Bezier.Envelope where
|
||||
|
||||
-- acts
|
||||
import Data.Act
|
||||
( Torsor((-->)) )
|
||||
|
||||
-- deepseq
|
||||
import Control.DeepSeq
|
||||
( NFData )
|
||||
|
||||
-- primitive
|
||||
import Data.Primitive.Types
|
||||
( Prim )
|
||||
|
||||
-- MetaBrush
|
||||
import Math.Roots
|
||||
( realRoots )
|
||||
import qualified Math.Bezier.Cubic as Cubic
|
||||
( Bezier(..), bezier, bezier' )
|
||||
import qualified Math.Bezier.Quadratic as Quadratic
|
||||
( Bezier(..), bezier, bezier' )
|
||||
import Math.Module
|
||||
( Module((^+^),(*^)), lerp, cross )
|
||||
import Math.Vector2D
|
||||
( Point2D(..), Vector2D(..), Segment(..) )
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
-- | Find the roots of the envelope equation for a family of cubic Bézier curves
|
||||
-- varying along a cubic Bézier path.
|
||||
--
|
||||
-- \[ c(t,u) = p(t) + b(t,u), \]
|
||||
--
|
||||
-- where \( t \mapsto p(t) \) describes the underlying path,
|
||||
-- and \( u \mapsto b(t_0,u) \) describes the brush shape at point \( t = t_0 \).
|
||||
--
|
||||
-- The envelope equation is then:
|
||||
--
|
||||
-- \[ \frac{\partial c}{\partial t} \cross \frac{\partial c}{\partial u} = 0. \]
|
||||
--
|
||||
-- Given \( t_0 \), this function returns a (possibly empty) list of values \( u_i \)
|
||||
-- satisfying the envelope equation at \( (t_0, u_i) \).
|
||||
--
|
||||
-- The points \( c(t_0,u_i) \) are thus potential outline points on the contour stroked
|
||||
-- by the brush as it moves along the path.
|
||||
envelope33
|
||||
:: forall r
|
||||
. ( RealFloat r, Prim r, NFData r )
|
||||
=> Cubic.Bezier ( Point2D r ) -> Cubic.Bezier ( Cubic.Bezier ( Point2D r ) ) -> r -> [ r ]
|
||||
envelope33 path
|
||||
( Cubic.Bezier
|
||||
( Cubic.Bezier b00 b01 b02 b03 )
|
||||
( Cubic.Bezier b10 b11 b12 b13 )
|
||||
( Cubic.Bezier b20 b21 b22 b23 )
|
||||
( Cubic.Bezier b30 b31 b32 b33 )
|
||||
) t0 = realRoots 50 [ a5, a4, a3, a2, a1, a0 ]
|
||||
|
||||
where
|
||||
|
||||
-- Compute ∂p/∂t(t0).
|
||||
dpdt :: Vector2D r
|
||||
dpdt = Cubic.bezier' @( Vector2D r ) path t0
|
||||
|
||||
-- Compute ∂b/∂t(t0,u) using the Bernstein basis:
|
||||
--
|
||||
-- ∂b/∂t(t0,u) = Cubic.bezier ( Cubic.Bezier ct0 ct1 ct2 ct3 ) u.
|
||||
ct0, ct1, ct2, ct3, dt0, dt1, dt2, dt3 :: Vector2D r
|
||||
ct0 = Cubic.bezier' @( Vector2D r ) ( Cubic.Bezier b00 b10 b20 b30 ) t0
|
||||
ct1 = Cubic.bezier' @( Vector2D r ) ( Cubic.Bezier b01 b11 b21 b31 ) t0
|
||||
ct2 = Cubic.bezier' @( Vector2D r ) ( Cubic.Bezier b02 b12 b22 b32 ) t0
|
||||
ct3 = Cubic.bezier' @( Vector2D r ) ( Cubic.Bezier b03 b13 b23 b33 ) t0
|
||||
|
||||
-- Add ∂p/∂t and convert the Bernstein representation to the monomial basis to obtain
|
||||
--
|
||||
-- ∂c/∂t(t0,u) = dt0 + u dt1 + u² dt2 + u³ dt3.
|
||||
dt0 = ct0 ^+^ dpdt
|
||||
dt1 = 3 *^ ( ct0 --> ct1 )
|
||||
dt2 = 3 *^ ( ct1 --> ct0 ^+^ ct1 --> ct2 )
|
||||
dt3 = ct0 --> ct3 ^+^ 3 *^ ( ct2 --> ct1 )
|
||||
|
||||
-- Compute ∂c/∂u(t0,u) using the Bernstein basis:
|
||||
--
|
||||
-- ∂c/∂u(t0,u) = Cubic.bezier' ( Cubic.Bezier cu0 cu1 cu2 cu3 ) u.
|
||||
cu0, cu1, cu2, cu3 :: Point2D r
|
||||
cu0 = Cubic.bezier @( Vector2D r ) ( Cubic.Bezier b00 b10 b20 b30 ) t0
|
||||
cu1 = Cubic.bezier @( Vector2D r ) ( Cubic.Bezier b01 b11 b21 b31 ) t0
|
||||
cu2 = Cubic.bezier @( Vector2D r ) ( Cubic.Bezier b02 b12 b22 b32 ) t0
|
||||
cu3 = Cubic.bezier @( Vector2D r ) ( Cubic.Bezier b03 b13 b23 b33 ) t0
|
||||
|
||||
-- Convert the Bernstein representation to the monomial basis to obtain
|
||||
--
|
||||
-- ∂c/∂u(t0,u) = du0 + u du1 + u² du2.
|
||||
du0, du1, du2 :: Vector2D r
|
||||
du0 = cu0 --> cu1
|
||||
du1 = 2 *^ ( cu1 --> cu0 ^+^ cu1 --> cu2 )
|
||||
du2 = cu0 --> cu3 ^+^ 3 *^ ( cu2 --> cu1 )
|
||||
|
||||
-- Expand out the cross-product ∂c/∂t × ∂c/∂u to obtain the envelope equation:
|
||||
--
|
||||
-- a0 + a1 u + a2 u² + a3 u³ + a4 u⁴ + a5 u⁵.
|
||||
a0, a1, a2, a3, a4, a5 :: r
|
||||
a0 = dt0 `cross` du0
|
||||
a1 = dt1 `cross` du0 + dt0 `cross` du1
|
||||
a2 = dt2 `cross` du0 + dt1 `cross` du1 + dt0 `cross` du2
|
||||
a3 = dt3 `cross` du0 + dt2 `cross` du1 + dt1 `cross` du2
|
||||
a4 = dt3 `cross` du1 + dt2 `cross` du2
|
||||
a5 = dt3 `cross` du2
|
||||
|
||||
-- | Find the roots of the envelope equation for a family of cubic Bézier curves
|
||||
-- varying along a quadratic Bézier path.
|
||||
--
|
||||
-- See 'envelope33' for more information.
|
||||
envelope23
|
||||
:: forall r
|
||||
. ( RealFloat r, Prim r, NFData r )
|
||||
=> Quadratic.Bezier ( Point2D r ) -> Quadratic.Bezier ( Cubic.Bezier ( Point2D r ) ) -> r -> [ r ]
|
||||
envelope23 path
|
||||
( Quadratic.Bezier
|
||||
( Cubic.Bezier b00 b01 b02 b03 )
|
||||
( Cubic.Bezier b10 b11 b12 b13 )
|
||||
( Cubic.Bezier b20 b21 b22 b23 )
|
||||
) t0 = realRoots 50 [ a5, a4, a3, a2, a1, a0 ]
|
||||
|
||||
where
|
||||
|
||||
dpdt :: Vector2D r
|
||||
dpdt = Quadratic.bezier' @( Vector2D r ) path t0
|
||||
|
||||
ct0, ct1, ct2, ct3, dt0, dt1, dt2, dt3 :: Vector2D r
|
||||
ct0 = Quadratic.bezier' @( Vector2D r ) ( Quadratic.Bezier b00 b10 b20 ) t0
|
||||
ct1 = Quadratic.bezier' @( Vector2D r ) ( Quadratic.Bezier b01 b11 b21 ) t0
|
||||
ct2 = Quadratic.bezier' @( Vector2D r ) ( Quadratic.Bezier b02 b12 b22 ) t0
|
||||
ct3 = Quadratic.bezier' @( Vector2D r ) ( Quadratic.Bezier b03 b13 b23 ) t0
|
||||
|
||||
dt0 = ct0 ^+^ dpdt
|
||||
dt1 = 3 *^ ( ct0 --> ct1 )
|
||||
dt2 = 3 *^ ( ct1 --> ct0 ^+^ ct1 --> ct2 )
|
||||
dt3 = ct0 --> ct3 ^+^ 3 *^ ( ct2 --> ct1 )
|
||||
|
||||
cu0, cu1, cu2, cu3 :: Point2D r
|
||||
cu0 = Quadratic.bezier @( Vector2D r ) ( Quadratic.Bezier b00 b10 b20 ) t0
|
||||
cu1 = Quadratic.bezier @( Vector2D r ) ( Quadratic.Bezier b01 b11 b21 ) t0
|
||||
cu2 = Quadratic.bezier @( Vector2D r ) ( Quadratic.Bezier b02 b12 b22 ) t0
|
||||
cu3 = Quadratic.bezier @( Vector2D r ) ( Quadratic.Bezier b03 b13 b23 ) t0
|
||||
|
||||
du0, du1, du2 :: Vector2D r
|
||||
du0 = cu0 --> cu1
|
||||
du1 = 2 *^ ( cu1 --> cu0 ^+^ cu1 --> cu2 )
|
||||
du2 = cu0 --> cu3 ^+^ 3 *^ ( cu2 --> cu1 )
|
||||
|
||||
a0, a1, a2, a3, a4, a5 :: r
|
||||
a0 = dt0 `cross` du0
|
||||
a1 = dt1 `cross` du0 + dt0 `cross` du1
|
||||
a2 = dt2 `cross` du0 + dt1 `cross` du1 + dt0 `cross` du2
|
||||
a3 = dt3 `cross` du0 + dt2 `cross` du1 + dt1 `cross` du2
|
||||
a4 = dt3 `cross` du1 + dt2 `cross` du2
|
||||
a5 = dt3 `cross` du2
|
||||
|
||||
-- | Find the roots of the envelope equation for a family of cubic Bézier curves
|
||||
-- varying along a straight line path.
|
||||
--
|
||||
-- See 'envelope33' for more information.
|
||||
envelope13
|
||||
:: forall r
|
||||
. ( RealFloat r, Prim r, NFData r )
|
||||
=> Segment ( Point2D r ) -> Segment ( Cubic.Bezier ( Point2D r ) ) -> r -> [ r ]
|
||||
envelope13 ( Segment p0 p1 )
|
||||
( Segment
|
||||
( Cubic.Bezier b00 b01 b02 b03 )
|
||||
( Cubic.Bezier b10 b11 b12 b13 )
|
||||
) t0 = realRoots 50 [ a5, a4, a3, a2, a1, a0 ]
|
||||
|
||||
where
|
||||
|
||||
dpdt :: Vector2D r
|
||||
dpdt = p0 --> p1
|
||||
|
||||
ct0, ct1, ct2, ct3, dt0, dt1, dt2, dt3 :: Vector2D r
|
||||
ct0 = b00 --> b10
|
||||
ct1 = b01 --> b11
|
||||
ct2 = b02 --> b12
|
||||
ct3 = b03 --> b13
|
||||
|
||||
dt0 = ct0 ^+^ dpdt
|
||||
dt1 = 3 *^ ( ct0 --> ct1 )
|
||||
dt2 = 3 *^ ( ct1 --> ct0 ^+^ ct1 --> ct2 )
|
||||
dt3 = ct0 --> ct3 ^+^ 3 *^ ( ct2 --> ct1 )
|
||||
|
||||
cu0, cu1, cu2, cu3 :: Point2D r
|
||||
cu0 = lerp @( Vector2D r ) t0 b00 b10
|
||||
cu1 = lerp @( Vector2D r ) t0 b01 b11
|
||||
cu2 = lerp @( Vector2D r ) t0 b02 b12
|
||||
cu3 = lerp @( Vector2D r ) t0 b03 b13
|
||||
|
||||
du0, du1, du2 :: Vector2D r
|
||||
du0 = cu0 --> cu1
|
||||
du1 = 2 *^ ( cu1 --> cu0 ^+^ cu1 --> cu2 )
|
||||
du2 = cu0 --> cu3 ^+^ 3 *^ ( cu2 --> cu1 )
|
||||
|
||||
a0, a1, a2, a3, a4, a5 :: r
|
||||
a0 = dt0 `cross` du0
|
||||
a1 = dt1 `cross` du0 + dt0 `cross` du1
|
||||
a2 = dt2 `cross` du0 + dt1 `cross` du1 + dt0 `cross` du2
|
||||
a3 = dt3 `cross` du0 + dt2 `cross` du1 + dt1 `cross` du2
|
||||
a4 = dt3 `cross` du1 + dt2 `cross` du2
|
||||
a5 = dt3 `cross` du2
|
||||
|
||||
-- | Find the roots of the envelope equation for a family of quadratic Bézier curves
|
||||
-- varying along a cubic Bézier path.
|
||||
--
|
||||
-- See 'envelope33' for more information.
|
||||
envelope32
|
||||
:: forall r
|
||||
. ( RealFloat r, Prim r, NFData r )
|
||||
=> Cubic.Bezier ( Point2D r ) -> Cubic.Bezier ( Quadratic.Bezier ( Point2D r ) ) -> r -> [ r ]
|
||||
envelope32 path
|
||||
( Cubic.Bezier
|
||||
( Quadratic.Bezier b00 b01 b02 )
|
||||
( Quadratic.Bezier b10 b11 b12 )
|
||||
( Quadratic.Bezier b20 b21 b22 )
|
||||
( Quadratic.Bezier b30 b31 b32 )
|
||||
) t0 = realRoots 50 [ a3, a2, a1, a0 ]
|
||||
|
||||
where
|
||||
|
||||
dpdt :: Vector2D r
|
||||
dpdt = Cubic.bezier' @( Vector2D r ) path t0
|
||||
|
||||
ct0, ct1, ct2, dt0, dt1, dt2 :: Vector2D r
|
||||
ct0 = Cubic.bezier' @( Vector2D r ) ( Cubic.Bezier b00 b10 b20 b30 ) t0
|
||||
ct1 = Cubic.bezier' @( Vector2D r ) ( Cubic.Bezier b01 b11 b21 b31 ) t0
|
||||
ct2 = Cubic.bezier' @( Vector2D r ) ( Cubic.Bezier b02 b12 b22 b32 ) t0
|
||||
|
||||
dt0 = ct0 ^+^ dpdt
|
||||
dt1 = 2 *^ ( ct0 --> ct1 )
|
||||
dt2 = ct1 --> ct0 ^+^ ct1 --> ct2
|
||||
|
||||
cu0, cu1, cu2 :: Point2D r
|
||||
cu0 = Cubic.bezier @( Vector2D r ) ( Cubic.Bezier b00 b10 b20 b30 ) t0
|
||||
cu1 = Cubic.bezier @( Vector2D r ) ( Cubic.Bezier b01 b11 b21 b31 ) t0
|
||||
cu2 = Cubic.bezier @( Vector2D r ) ( Cubic.Bezier b02 b12 b22 b32 ) t0
|
||||
|
||||
du0, du1 :: Vector2D r
|
||||
du0 = cu0 --> cu1
|
||||
du1 = cu1 --> cu0 ^+^ cu1 --> cu2
|
||||
|
||||
a0, a1, a2, a3 :: r
|
||||
a0 = dt0 `cross` du0
|
||||
a1 = dt1 `cross` du0 + dt0 `cross` du1
|
||||
a2 = dt2 `cross` du0 + dt1 `cross` du1
|
||||
a3 = dt2 `cross` du1
|
||||
|
||||
-- | Find the roots of the envelope equation for a family of quadratic Bézier curves
|
||||
-- varying along a quadratic Bézier path.
|
||||
--
|
||||
-- See 'envelope33' for more information.
|
||||
envelope22
|
||||
:: forall r
|
||||
. ( RealFloat r, Prim r, NFData r )
|
||||
=> Quadratic.Bezier ( Point2D r ) -> Quadratic.Bezier ( Quadratic.Bezier ( Point2D r ) ) -> r -> [ r ]
|
||||
envelope22 path
|
||||
( Quadratic.Bezier
|
||||
( Quadratic.Bezier b00 b01 b02 )
|
||||
( Quadratic.Bezier b10 b11 b12 )
|
||||
( Quadratic.Bezier b20 b21 b22 )
|
||||
) t0 = realRoots 50 [ a3, a2, a1, a0 ]
|
||||
|
||||
where
|
||||
|
||||
dpdt :: Vector2D r
|
||||
dpdt = Quadratic.bezier' @( Vector2D r ) path t0
|
||||
|
||||
ct0, ct1, ct2, dt0, dt1, dt2 :: Vector2D r
|
||||
ct0 = Quadratic.bezier' @( Vector2D r ) ( Quadratic.Bezier b00 b10 b20 ) t0
|
||||
ct1 = Quadratic.bezier' @( Vector2D r ) ( Quadratic.Bezier b01 b11 b21 ) t0
|
||||
ct2 = Quadratic.bezier' @( Vector2D r ) ( Quadratic.Bezier b02 b12 b22 ) t0
|
||||
|
||||
dt0 = ct0 ^+^ dpdt
|
||||
dt1 = 2 *^ ( ct0 --> ct1 )
|
||||
dt2 = ct1 --> ct0 ^+^ ct1 --> ct2
|
||||
|
||||
cu0, cu1, cu2 :: Point2D r
|
||||
cu0 = Quadratic.bezier @( Vector2D r ) ( Quadratic.Bezier b00 b10 b20 ) t0
|
||||
cu1 = Quadratic.bezier @( Vector2D r ) ( Quadratic.Bezier b01 b11 b21 ) t0
|
||||
cu2 = Quadratic.bezier @( Vector2D r ) ( Quadratic.Bezier b02 b12 b22 ) t0
|
||||
|
||||
du0, du1 :: Vector2D r
|
||||
du0 = cu0 --> cu1
|
||||
du1 = cu1 --> cu0 ^+^ cu1 --> cu2
|
||||
|
||||
a0, a1, a2, a3 :: r
|
||||
a0 = dt0 `cross` du0
|
||||
a1 = dt1 `cross` du0 + dt0 `cross` du1
|
||||
a2 = dt2 `cross` du0 + dt1 `cross` du1
|
||||
a3 = dt2 `cross` du1
|
||||
|
||||
-- | Find the roots of the envelope equation for a family of quadratic Bézier curves
|
||||
-- varying along a straight line.
|
||||
--
|
||||
-- See 'envelope33' for more information.
|
||||
envelope12
|
||||
:: forall r
|
||||
. ( RealFloat r, Prim r, NFData r )
|
||||
=> Segment ( Point2D r ) -> Segment ( Quadratic.Bezier ( Point2D r ) ) -> r -> [ r ]
|
||||
envelope12 ( Segment p0 p1 )
|
||||
( Segment
|
||||
( Quadratic.Bezier b00 b01 b02 )
|
||||
( Quadratic.Bezier b10 b11 b12 )
|
||||
) t0 = realRoots 50 [ a3, a2, a1, a0 ]
|
||||
|
||||
where
|
||||
|
||||
dpdt :: Vector2D r
|
||||
dpdt = p0 --> p1
|
||||
|
||||
ct0, ct1, ct2, dt0, dt1, dt2 :: Vector2D r
|
||||
ct0 = b00 --> b10
|
||||
ct1 = b01 --> b11
|
||||
ct2 = b02 --> b12
|
||||
|
||||
dt0 = ct0 ^+^ dpdt
|
||||
dt1 = 2 *^ ( ct0 --> ct1 )
|
||||
dt2 = ct1 --> ct0 ^+^ ct1 --> ct2
|
||||
|
||||
cu0, cu1, cu2 :: Point2D r
|
||||
cu0 = lerp @( Vector2D r ) t0 b00 b10
|
||||
cu1 = lerp @( Vector2D r ) t0 b01 b11
|
||||
cu2 = lerp @( Vector2D r ) t0 b02 b12
|
||||
|
||||
du0, du1 :: Vector2D r
|
||||
du0 = cu0 --> cu1
|
||||
du1 = cu1 --> cu0 ^+^ cu1 --> cu2
|
||||
|
||||
a0, a1, a2, a3 :: r
|
||||
a0 = dt0 `cross` du0
|
||||
a1 = dt1 `cross` du0 + dt0 `cross` du1
|
||||
a2 = dt2 `cross` du0 + dt1 `cross` du1
|
||||
a3 = dt2 `cross` du1
|
||||
|
||||
-- | Find the roots of the envelope equation for a family of line segments
|
||||
-- varying along a cubic Bézier curve.
|
||||
--
|
||||
-- See 'envelope33' for more information.
|
||||
envelope31
|
||||
:: forall r
|
||||
. ( RealFloat r, Prim r, NFData r )
|
||||
=> Cubic.Bezier ( Point2D r ) -> Cubic.Bezier ( Segment ( Point2D r ) ) -> r -> [ r ]
|
||||
envelope31 path
|
||||
( Cubic.Bezier
|
||||
( Segment b00 b01 )
|
||||
( Segment b10 b11 )
|
||||
( Segment b20 b21 )
|
||||
( Segment b30 b31 )
|
||||
) t0 = [ - a1 / a0 ]
|
||||
|
||||
where
|
||||
|
||||
dpdt :: Vector2D r
|
||||
dpdt = Cubic.bezier' @( Vector2D r ) path t0
|
||||
|
||||
ct0, ct1, dt0, dt1 :: Vector2D r
|
||||
ct0 = Cubic.bezier' @( Vector2D r ) ( Cubic.Bezier b00 b10 b20 b30 ) t0
|
||||
ct1 = Cubic.bezier' @( Vector2D r ) ( Cubic.Bezier b01 b11 b21 b31 ) t0
|
||||
|
||||
dt0 = ct0 ^+^ dpdt
|
||||
dt1 = ct0 --> ct1
|
||||
|
||||
cu0, cu1 :: Point2D r
|
||||
cu0 = Cubic.bezier @( Vector2D r ) ( Cubic.Bezier b00 b10 b20 b30 ) t0
|
||||
cu1 = Cubic.bezier @( Vector2D r ) ( Cubic.Bezier b01 b11 b21 b31 ) t0
|
||||
|
||||
du0 :: Vector2D r
|
||||
du0 = cu0 --> cu1
|
||||
|
||||
a0, a1 :: r
|
||||
a0 = dt0 `cross` du0
|
||||
a1 = dt1 `cross` du0
|
||||
|
||||
-- | Find the roots of the envelope equation for a family of line segments
|
||||
-- varying along a quadratic Bézier curve.
|
||||
--
|
||||
-- See 'envelope33' for more information.
|
||||
envelope21
|
||||
:: forall r
|
||||
. ( RealFloat r, Prim r, NFData r )
|
||||
=> Quadratic.Bezier ( Point2D r ) -> Quadratic.Bezier ( Segment ( Point2D r ) ) -> r -> [ r ]
|
||||
envelope21 path
|
||||
( Quadratic.Bezier
|
||||
( Segment b00 b01 )
|
||||
( Segment b10 b11 )
|
||||
( Segment b20 b21 )
|
||||
) t0 = [ - a1 / a0 ]
|
||||
|
||||
where
|
||||
|
||||
dpdt :: Vector2D r
|
||||
dpdt = Quadratic.bezier' @( Vector2D r ) path t0
|
||||
|
||||
ct0, ct1, dt0, dt1 :: Vector2D r
|
||||
ct0 = Quadratic.bezier' @( Vector2D r ) ( Quadratic.Bezier b00 b10 b20 ) t0
|
||||
ct1 = Quadratic.bezier' @( Vector2D r ) ( Quadratic.Bezier b01 b11 b21 ) t0
|
||||
|
||||
dt0 = ct0 ^+^ dpdt
|
||||
dt1 = ct0 --> ct1
|
||||
|
||||
cu0, cu1 :: Point2D r
|
||||
cu0 = Quadratic.bezier @( Vector2D r ) ( Quadratic.Bezier b00 b10 b20 ) t0
|
||||
cu1 = Quadratic.bezier @( Vector2D r ) ( Quadratic.Bezier b01 b11 b21 ) t0
|
||||
|
||||
du0 :: Vector2D r
|
||||
du0 = cu0 --> cu1
|
||||
|
||||
a0, a1 :: r
|
||||
a0 = dt0 `cross` du0
|
||||
a1 = dt1 `cross` du0
|
||||
|
||||
-- | Find the roots of the envelope equation for a family of line segments
|
||||
-- varying along a straight line path.
|
||||
--
|
||||
-- See 'envelope33' for more information.
|
||||
envelope11
|
||||
:: forall r
|
||||
. ( RealFloat r, Prim r, NFData r )
|
||||
=> Segment ( Point2D r ) -> Segment ( Segment ( Point2D r ) ) -> r -> [ r ]
|
||||
envelope11 ( Segment p0 p1 )
|
||||
( Segment
|
||||
( Segment b00 b01 )
|
||||
( Segment b10 b11 )
|
||||
) t0 = [ - a1 / a0 ]
|
||||
|
||||
where
|
||||
|
||||
dpdt :: Vector2D r
|
||||
dpdt = p0 --> p1
|
||||
|
||||
ct0, ct1, dt0, dt1 :: Vector2D r
|
||||
ct0 = b00 --> b10
|
||||
ct1 = b01 --> b11
|
||||
|
||||
dt0 = ct0 ^+^ dpdt
|
||||
dt1 = ct0 --> ct1
|
||||
|
||||
cu0, cu1 :: Point2D r
|
||||
cu0 = lerp @( Vector2D r ) t0 b00 b10
|
||||
cu1 = lerp @( Vector2D r ) t0 b01 b11
|
||||
|
||||
du0 :: Vector2D r
|
||||
du0 = cu0 --> cu1
|
||||
|
||||
a0, a1 :: r
|
||||
a0 = dt0 `cross` du0
|
||||
a1 = dt1 `cross` du0
|
||||
Loading…
Reference in a new issue