There is some discussion here about fill-pen http://www.mail-archive.com/[email protected]/msg02019.html

But I can't see documentation about cubic, diamond, etc... effect for fill-pen in rebol's official doc ?

I'm trying to draw some round rectangle with glowing effect but don't really understand the parameters I'm playing with so I can't get exactly what I'd like (I'd like the glow effect starting from the center not from the dark left top corner):

view layout [
    box 278x185 effect [ ; default box face size is 100x100
      draw [
        anti-alias on
        ; information for the next draw element (not required)
        line-width 2.5 ; number of pixels in width of the border
        pen black      ; color of the edge of the next draw element

        ; fill pen is a little complex:
        ;fill-pen 10x10 0 90 0 1 1 0.0.0 255.0.0 255.0.255
        fill-pen radial 20x20 5 55 5 5 10 0.0.0 55.0.5 55.0.5

        ; the draw element
        box     ; another box drawn as an effect
          15     ; size of rounding in pixels
          0x0 ; upper left corner
          278x170 ; lower right corner
      ]
    ]
]