使用Haskell GLUT绑定,我修改了Hello World示例两个方面:
- 将
initialDisplayMode
添加WithAlphaComponent
。 - 将颜色更改为
Color4
,不透明度为0.5
。
import Graphics.UI.GLUT
display :: DisplayCallback
display = do
-- clear all pixels
clear [ ColorBuffer ]
-- draw white polygon (rectangle) with corners at
-- (0.25, 0.25, 0.0) and (0.75, 0.75, 0.0)
-- CHANGE #2
color (Color4 1.0 1.0 (1.0 :: GLfloat) 0.5)
-- resolve overloading, not needed in "real" programs
let vertex3f = vertex :: Vertex3 GLfloat -> IO ()
renderPrimitive Polygon $ mapM_ vertex3f [
Vertex3 0.25 0.25 0.0,
Vertex3 0.75 0.25 0.0,
Vertex3 0.75 0.75 0.0,
Vertex3 0.25 0.75 0.0]
-- don't wait!
-- start processing buffered OpenGL routines
flush
myInit :: IO ()
myInit = do
-- select clearing color
clearColor $= Color4 0.7 0 0 0
-- initialize viewing values
matrixMode $= Projection
loadIdentity
ortho 0 1 0 1 (-1) 1
-- Declare initial window size, position, and display mode (single buffer and
-- RGBA). Open window with "hello" in its title bar. Call initialization
-- routines. Register callback function to display graphics. Enter main loop and
-- process events.
main :: IO ()
main = do
_ <- getArgsAndInitialize
-- CHANGE #1
initialDisplayMode $= [ SingleBuffered, RGBMode, WithAlphaComponent ]
initialWindowSize $= Size 250 250
initialWindowPosition $= Position 100 100
_ <- createWindow "hello"
myInit
displayCallback $= display
mainLoop
glEnable(GL_BLEND)
实现。不确定在 Haskell 中应该如何操作。 - Nico Schertler