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From: kasper@csli.STANFORD.EDU (Kasper Osterbye)
Newsgroups: comp.sys.amiga.tech,comp.sys.amiga
Subject: How to smooth scroll left?
Message-ID: <3313@csli.STANFORD.EDU>
Date: 4 Apr 88 19:10:26 GMT
References: <4861@ecsvax.UUCP>
Reply-To: kasper@csli.UUCP (Kasper Osterbye)
Organization: Center for the Study of Language and Information, Stanford U.
Lines: 23

Hi,

I wanted to write a little game. In that little game I wanted a background
to scroll smoothly to the left. It prooved to be more difficult than I
hoped for. Here is what I did, but it is utterly slow.

I make an off-screen rasterport to draw into, so that I should not have to
scroll the rasterport on the screen (I use a HIRES 16 color screen - to big?)

My scroll loop looks like this
	Scroll of screen rasterport 1 to the left
		Using the build in rasterscroll.
	Draw one vertical line of new background.
	Copy the off-screen raster to the Screen raster
		Using the BltBitMapRasterPort procedure.


This came out hopelessly slow, so what do I do? 
- Take a low res low color screen
- use BltBitMap directly (is there a win there?)
- Apply amiga-guro trick #71.4 for smooth scrolling backgrounds, only I
  do not know that trick

-- Kasper