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From: spence@cbmvax.commodore.com (Spencer Shanson)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: hardware sprites
Keywords: sprites
Message-ID: <22303@cbmvax.commodore.com>
Date: 10 Jun 91 17:47:01 GMT
References: <19672@csli.Stanford.EDU> <2979@public.BTR.COM> <22258@cbmvax.commodore.com> <2987@public.BTR.COM>
Reply-To: spence@cbmvax.commodore.com (Spencer Shanson)
Organization: Commodore, West Chester, PA
Lines: 47


In article <2987@public.BTR.COM> valentin@public.BTR.COM (Valentin Pepelea) writes:
>In article <22258@cbmvax.commodore.com> spence@cbmvax.commodore.com (Spencer
>Shanson) writes:
>>
>>Valentin, ChangeSprite() has to MoveSprite(), whereas FreeSprite()
>>is much simpler - point the sprite to a default sprite of 0s. I would be
>>surprised if you have found ChangeSprite() to be faster than FreeSprite().
>
>On the other hand, restoring the sprite will require an additional call to
>GetSprite(). So the question is whether FreeSprite() and GetSprite() together
>are faster than just ChangeSprite(), praticularly when you take into account 
>the overhead of calling these functions. There are advantages to having access
>to the source code, so why don't you tell me.
>
OK - we can either:
1) ChangeSprite() to offscreen
2) ChangeSprite() to onscreen

or

1) FreeSprite()
2) GetSprite()
3) ChangeSprite()

Now, GetSprite() is another simple function, whereas MoveSprite(), which is called
indirectly when you use ChangeSprite(), is a relatively complex piece of code. So
because a FreeSprite()/GetSprite() combination is one less call to ChangeSprite(), I
believe it would be the faster method *from code inspection*. I haven't proved it
though with experimentation.


>Valentin
>-- 
>"An operating system without virtual memory      Name:      Valentin Pepelea
> is an operating system without virtue."         Phone:     (408) 985-1700
>                                                 Usenet:    mips!btr!valentin
>                     - Ancient Inca Proverb      Internet:  valentin@btr.com


-- 
---------------------------------------------------------------------------
Spencer Shanson - Amiga Software Engineer     | email: spence@commodore.COM
                                              | or uunet!cbmvax!spence
All opinions expressed are my own, and do not | Bix: sshanson
(necessarily) represent those of Commodore.   | "Copper? I hardly even
                                              | know her!"