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{-
Stencil.hs (adapted from stencil.c which is (c) Silicon Graphics, Inc.)
Copyright (c) Sven Panne 2002-2006 <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 use of the stencil buffer for masking
nonrectangular regions. Whenever the window is redrawn, a value of 1 is drawn
into a diamond-shaped region in the stencil buffer. Elsewhere in the stencil
buffer, the value is 0. Then a blue sphere is drawn where the stencil value
is 1, and yellow torii are drawn where the stencil value is not 1.
-}
import System.Exit ( exitWith, ExitCode(ExitSuccess) )
import Graphics.UI.GLUT
data DisplayLists = DisplayLists { yellowMat, blueMat :: DisplayList }
myInit :: IO DisplayLists
myInit = do
y <- defineNewList Compile $ do
materialDiffuse Front $= Color4 0.7 0.7 0 1
materialSpecular Front $= Color4 1 1 1 1
materialShininess Front $= 64
b <- defineNewList Compile $ do
materialDiffuse Front $= Color4 0.1 0.1 0.7 1
materialSpecular Front $= Color4 0.1 1 1 1
materialShininess Front $= 45
position (Light 0) $= Vertex4 1 1 1 0
light (Light 0) $= Enabled
lighting $= Enabled
depthFunc $= Just Less
clearStencil $= 0
stencilTest $= Enabled
return $ DisplayLists { yellowMat = y, blueMat = b }
-- Draw a sphere in a diamond-shaped section in the middle of a window with 2
-- torii.
display :: DisplayLists -> DisplayCallback
display displayLists = do
clear [ ColorBuffer, DepthBuffer ]
-- draw blue sphere where the stencil is 1
stencilFunc $= (Equal, 1, 1)
stencilOp $= (OpKeep, OpKeep, OpKeep)
callList (blueMat displayLists)
renderObject Solid (Sphere' 0.5 15 15)
-- resolve overloading, not needed in "real" programs
let rotatef = rotate :: GLfloat -> Vector3 GLfloat -> IO ()
-- draw the tori where the stencil is not 1
stencilFunc $= (Notequal, 1, 1)
preservingMatrix $ do
rotatef 45 (Vector3 0 0 1)
rotatef 45 (Vector3 0 1 0)
callList (yellowMat displayLists)
renderObject Solid (Torus 0.275 0.85 15 15)
preservingMatrix $ do
rotatef 90 (Vector3 1 0 0)
renderObject Solid (Torus 0.275 0.85 15 15)
flush
-- Whenever the window is reshaped, redefine the coordinate system and redraw
-- the stencil area.
reshape :: ReshapeCallback
reshape size@(Size w h) = do
viewport $= (Position 0 0, size)
-- create a diamond shaped stencil area
matrixMode $= Projection
loadIdentity
let wf = fromIntegral w
hf = fromIntegral h
if w <= h
then ortho2D (-3) 3 (-3*hf/wf) (3*hf/wf)
else ortho2D (-3*wf/hf) (3*wf/hf) (-3) 3
matrixMode $= Modelview 0
loadIdentity
-- resolve overloading, not needed in "real" programs
let vertex2f = vertex :: Vertex2 GLfloat -> IO ()
translatef = translate :: Vector3 GLfloat -> IO ()
clear [ StencilBuffer ]
stencilFunc $= (Always, 1, 1)
stencilOp $= (OpReplace, OpReplace, OpReplace)
renderPrimitive Quads $ do
vertex2f (Vertex2 (-1) 0)
vertex2f (Vertex2 0 1)
vertex2f (Vertex2 1 0)
vertex2f (Vertex2 0 (-1))
matrixMode $= Projection
loadIdentity
perspective 45 (wf/hf) 3 7
matrixMode $= Modelview 0
loadIdentity
translatef (Vector3 0 0 (-5))
keyboard :: KeyboardMouseCallback
keyboard (Char '\27') Down _ _ = exitWith ExitSuccess
keyboard _ _ _ _ = return ()
-- Main Loop: Be certain to request stencil bits.
main :: IO ()
main = do
(progName, _args) <- getArgsAndInitialize
initialDisplayMode $= [ SingleBuffered, RGBMode, WithDepthBuffer, WithStencilBuffer ]
initialWindowSize $= Size 400 400
initialWindowPosition $= Position 100 100
createWindow progName
displayLists <- myInit
reshapeCallback $= Just reshape
keyboardMouseCallback $= Just keyboard
displayCallback $= display displayLists
mainLoop
|
