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{-
Tess.hs (adapted from tess.c which is (c) Silicon Graphics, Inc)
Copyright (c) Sven Panne 2002-2005 <sven.panne@aedion.de>
This file is part of HOpenGL and distributed under a BSD-style license
See the file libraries/GLUT/LICENSE
This program demonstrates polygon tessellation. Two tesselated objects are
drawn. The first is a rectangle with a triangular hole. The second is a
smooth shaded, self-intersecting star.
Note the exterior rectangle is drawn with its vertices in counter-clockwise
order, but its interior clockwise. Note the combineCallback is needed for the
self-intersecting star. Also note that removing the TessProperty for the
star will make the interior unshaded (TessWindingOdd).
-}
import System.Exit ( exitWith, ExitCode(ExitSuccess) )
import Graphics.UI.GLUT
display :: [DisplayList] -> DisplayCallback
display displayLists = do
clear [ ColorBuffer ]
-- resolve overloading, not needed in "real" programs
let color3f = color :: Color3 GLfloat -> IO ()
color3f (Color3 1 1 1)
mapM callList displayLists
flush
-- 'Float' is a dummy, any marshalable type would do
type DontCare = Float
rectangle :: ComplexContour DontCare
rectangle = ComplexContour [
AnnotatedVertex (Vertex3 50 50 0) 0,
AnnotatedVertex (Vertex3 200 50 0) 0,
AnnotatedVertex (Vertex3 200 200 0) 0,
AnnotatedVertex (Vertex3 50 200 0) 0 ]
tri :: ComplexContour DontCare
tri = ComplexContour [
AnnotatedVertex (Vertex3 75 75 0) 0,
AnnotatedVertex (Vertex3 125 175 0) 0,
AnnotatedVertex (Vertex3 175 75 0) 0 ]
rectAndTri :: ComplexPolygon DontCare
rectAndTri = ComplexPolygon [ rectangle, tri ]
noOpCombiner :: Combiner DontCare
noOpCombiner _newVertex _weightedProperties = 0
star :: ComplexPolygon (Color3 GLfloat)
star = ComplexPolygon [
ComplexContour [
AnnotatedVertex (Vertex3 250 50 0) (Color3 1 0 1),
AnnotatedVertex (Vertex3 325 200 0) (Color3 1 1 0),
AnnotatedVertex (Vertex3 400 50 0) (Color3 0 1 1),
AnnotatedVertex (Vertex3 250 150 0) (Color3 1 0 0),
AnnotatedVertex (Vertex3 400 150 0) (Color3 0 1 0) ] ]
combineColors :: Combiner (Color3 GLfloat)
combineColors
_newVertex
(WeightedProperties
(w0, Color3 r0 g0 b0)
(w1, Color3 r1 g1 b1)
(w2, Color3 r2 g2 b2)
(w3, Color3 r3 g3 b3)) =
Color3 (w0*r0 + w1*r1 + w2*r2 + w3*r3)
(w0*g0 + w1*g1 + w2*g2 + w3*g3)
(w0*b0 + w1*b1 + w2*b2 + w3*b3)
myInit :: IO [DisplayList]
myInit = do
clearColor $= Color4 0 0 0 0
rectAndTriList <- defineNewList Compile $
drawSimplePolygon (\_ -> return ()) =<<
tessellate TessWindingOdd 0 (Normal3 0 0 0) noOpCombiner rectAndTri
starList <- defineNewList Compile $
drawSimplePolygon color =<<
tessellate TessWindingPositive 0 (Normal3 0 0 0) combineColors star
return [ rectAndTriList, starList ]
drawSimplePolygon :: (v -> IO ()) -> SimplePolygon v -> IO ()
drawSimplePolygon colorHandler (SimplePolygon primitives) =
flip mapM_ primitives $ \(Primitive primitiveMode vertices) ->
renderPrimitive primitiveMode $
flip mapM_ vertices $ \(AnnotatedVertex plainVertex col) -> do
colorHandler col
vertex plainVertex
reshape :: ReshapeCallback
reshape size@(Size w h) = do
viewport $= (Position 0 0, size)
matrixMode $= Projection
loadIdentity
ortho2D 0 (fromIntegral w) 0 (fromIntegral h)
matrixMode $= Modelview 0
loadIdentity
keyboard :: KeyboardMouseCallback
keyboard (Char '\27') Down _ _ = exitWith ExitSuccess
keyboard _ _ _ _ = return ()
main :: IO ()
main = do
(progName, _args) <- getArgsAndInitialize
initialDisplayMode $= [ SingleBuffered, RGBMode ]
initialWindowSize $= Size 500 500
createWindow progName
displayLists <- myInit
displayCallback $= display displayLists
reshapeCallback $= Just reshape
keyboardMouseCallback $= Just keyboard
mainLoop
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