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{-
Triangulate.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 triangulation. 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 System.Random ( randomIO )
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 ]
star :: ComplexPolygon DontCare
star = ComplexPolygon [
ComplexContour [
AnnotatedVertex (Vertex3 250 50 0) 0,
AnnotatedVertex (Vertex3 325 200 0) 0,
AnnotatedVertex (Vertex3 400 50 0) 0,
AnnotatedVertex (Vertex3 250 150 0) 0,
AnnotatedVertex (Vertex3 400 150 0) 0 ] ]
myInit :: IO [DisplayList]
myInit = do
clearColor $= Color4 0 0 0 0
rectAndTriList <- compileNewList TessWindingOdd rectAndTri
starList <- compileNewList TessWindingPositive star
return [ rectAndTriList, starList ]
compileNewList :: TessWinding -> ComplexPolygon DontCare -> IO DisplayList
compileNewList windingRule complexPolygon =
defineNewList Compile $
drawTriangulation =<<
triangulate windingRule 0 (Normal3 0 0 0) noOpCombiner complexPolygon
noOpCombiner :: Combiner DontCare
noOpCombiner _newVertex _weightedProperties = 0
drawTriangulation :: Triangulation DontCare -> IO ()
drawTriangulation (Triangulation triangles) =
renderPrimitive Triangles $
flip mapM_ triangles $ \(Triangle tv1 tv2 tv3) -> do
randomColor
drawTriangleVertex tv1
drawTriangleVertex tv2
drawTriangleVertex tv3
randomColor :: IO ()
randomColor = do
r <- randomIO
g <- randomIO
b <- randomIO
-- resolve overloading, not needed in "real" programs
let color3f = color :: Color3 GLfloat -> IO ()
color3f (Color3 r g b)
drawTriangleVertex :: TriangleVertex DontCare -> IO ()
drawTriangleVertex (AnnotatedVertex plainVertex (_, e)) = do
edgeFlag $= e
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
|
