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From: uad1077@dircon.co.uk (Ian Kemmish)
Newsgroups: comp.lang.postscript
Subject: Re: multiple color fill?
Message-ID: <1991Jun22.152621.29945@dircon.co.uk>
Date: 22 Jun 91 15:26:21 GMT
References: <538@daily-planet.concordia.ca>
Organization: The Direct Connection, UK
Lines: 45

sotbill@vax2.concordia.ca writes:

>I asked this question before without success (not even an answer).
>Is it possible to do gradiant filling in postscript? Can I make
>a small subroutine (function) that will take points of a triangle
>and color at each of them and draw the triangle with interpolated
>colors inside the triangle without using "colorimage"? Do I have
>to use "colorimage"? Speed is not my main concern here.

>A while back, I read in PCMag review of vector based graphics
>translator that Postscript could do gradient fills. I have looked
>in the reference manual, but I could not find anything about it.
>The only reference I found so far was in the "green book", chapter
>8, where they show a square filled black to white using the
>"image" operator.

>That type of thing is done on Silicon Graphics workstations without
>a second thought.

>Any kind of help (references or other) on this will be welcome, thanx

>Richard Lefebvre
>sotbill@vax2.concordia.ca

Well, if enough of us holler loudly enough about it, maybe gradient
fills could be included as yet another special colour space in
PostScript Level 3?  It's certainly a very useful facility to
have.

Another possibility that I have been playing with, but which is
nowhere near commercial yet, is to have `shaders' like Renderman.

If you set the colour space to `shader' and the underlying space to
`DeviceRGB', then you might say something like
{ y 1 y sub 0 } setcolor
to define a shader which went [almost] smoothly from red to green
as the y co-ordinate varied....

Someday!

-- 
Ian D. Kemmish                    Tel. +44 767 601 361
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