Improve bezier curve rendering

src/Picture.hs

@@ -71,21 +71,23 @@ polygonCol = PolygonCol 0
 
 -- note that much of work computing the width of the bezier curve is done here
 bezierQuad :: Color -> Color -> Float -> Float -> Point2 -> Point2 -> Point2 -> Picture
-bezierQuad cola colc ra rc a b c = BezierQuad 0 [(aX,cola                 ,raX)
-                                                ,(bX,mixColors 0.5 0.5 cola colc,1)
-                                                ,(cX,colc                 ,rcX)]
-    where b2a | isLHS a b c = b -.- a
-              | otherwise   = a -.- b
-          nb2a = normalizeV $ vNormal b2a
-          aX = a +.+ ra * 0.5 *.* nb2a
-          b2c | isLHS a b c = c -.- b
-              | otherwise   = b -.- c
-          nb2c = normalizeV $ vNormal b2c
-          cX = c +.+ rc * 0.5 *.* nb2c
-          raX = ra / magV (aX -.- bX)
-          rcX = rc / magV (cX -.- bX)
-          bX = b +.+ (0.5 * ra *.* nb2a)
-                 +.+ (0.5 * rc *.* nb2c)
+bezierQuad cola colc ra rc a b c = BezierQuad 0 [(aX, cola, aX +.+ aRadVec , fracRadA  )
+                                                ,(bX, colb, (0,0)          , 0 )
+                                                ,(cX, colc, cX +.+ cRadVec , fracRadC )
+                                                ]
+    where colb = mixColors 0.5 0.5 cola colc
+          b2a | isLHS a b c = a -.- b
+              | otherwise   = b -.- a
+          aRadVec = ra *.* (normalizeV $ vNormal b2a)
+          aX = a -.- 0.5 *.* aRadVec
+          b2c | isLHS a b c = b -.- c
+              | otherwise   = c -.- b
+          cRadVec = rc *.* (normalizeV $ vNormal b2c)
+          cX = c -.- 0.5 *.* cRadVec
+          bX = (b -.- (0.5 * ra *.* aRadVec) )
+                  -.- (0.5 * rc *.* cRadVec)
+          fracRadA = ra / magV (aX -.- cX)
+          fracRadC = rc / magV (aX -.- cX)
 
 color :: RGBA -> Picture -> Picture
 {-# INLINE color #-}

src/Picture/Data.hs

@@ -22,7 +22,7 @@ import Data.Traversable
 
 data RenderType
     = RenderPoly [(Point3,Point4)]
-    | RenderBezQ [(Point3,Point4,Float)]
+    | RenderBezQ [(Point3,Point4,Point3)]
     | RenderText [(Point3,Point4,Point3)]
     | RenderArc  (Point3,Point4,Point4)
     | RenderLine [(Point3,Point4)]
@@ -75,7 +75,7 @@ data Picture
     = Blank
     | Text Int String
     | Polygon Int [Point2]
-    | BezierQuad Int [(Point2,RGBA,Float)]
+    | BezierQuad Int [(Point2,RGBA,Point2,Float)]
     | PolygonCol Int [(Point2,RGBA)]
     | Circle Int RGBA RGBA Float
     | ThickArc Int Float Float Float Float

src/Picture/Preload.hs

@@ -50,7 +50,7 @@ preloadRender = do
                                 "data/texture/charMap.png"
 
     bezierQuadShader
-           <- makeShader "bezierQuad" [vert,geom,frag] [(0,3),(1,4),(2,1)]    Triangles pokeBezQStrat
+           <- makeShader "bezierQuad" [vert,geom,frag] [(0,3),(1,4),(2,3)]    Triangles pokeBezQStrat
 
 --the following vbo is set up to contain one fixed vertex
     dummyvbo <- genObjectName
@@ -84,7 +84,7 @@ cleanUpRenderPreload pd = do
 
 {-# INLINE pokeBezQStrat #-}
 pokeBezQStrat :: RenderType -> [[[Float]]]
-pokeBezQStrat (RenderBezQ vs) = fmap (\((x,y,z),(r,g,b,a),s) -> [[x,y,z],[r,g,b,a],[s]]) vs
+pokeBezQStrat (RenderBezQ vs) = fmap (\((x,y,z),(r,g,b,a),(s,t,v)) -> [[x,y,z],[r,g,b,a],[s,t,v]]) vs
 pokeBezQStrat _ = []
 
 {-# INLINE pokeTriStrat #-}

src/Picture/Tree.hs

@@ -19,7 +19,8 @@ picToLTree mx (PolygonCol i vs)
         where (ps,cs) = unzip vs
 picToLTree mx (BezierQuad i vs) 
     = filtB mx i $ LLeaf $ RenderBezQ $ zip3 (map zeroZ ps) cols rs
-        where (ps,cols,rs) = unzip3 vs
+        where (ps,cols,offps,rads) = unzip4 vs
+              rs = zipWith (\(x,y) z -> (x,y,z)) offps rads
                                       
 picToLTree mx (Circle i colC colE r)
     = filtB mx i $ LLeaf $ RenderEllipse [( (-r, r,0), colC)