Re: [stella] tutorial progress

Subject: Re: [stella] tutorial progress
From: KirkIsrael@xxxxxxxxxxxxx
Date: 27 Jun 2002 18:56:56 -0000
> Your tutorial is great so far,  being a newbie I can allready see how much
> help it's going to be.
> 
> On your page about the VSYNC's and VBLANKS, it would be cool to see a simple
> little chart like when it's safe to do code and when it's not etc.   I'm
> sure your code in the "My First Program" section will go over all that
> though.

Yeah, actually, I had been toying with the idea of putting 
in similar things "do VSYNC here" "make sure VBLANK is on here"
etc in that first chart, maybe in a different color. It might be 
too confusing visually though...maybe I'll copy that chart, remove 
the cycle/scanline counts, and put it in that data.
 
Thanks to Andrew Davie, who made a bunch of suggestions...
(and i wrote him a longish e-mail but my crapwebmail program
ate it...) he had some minor improvments,
pointed out my NTSC (vs PAL) bias, and suggested some 
talk about the Kernel...I might not the 
slightly more advanced kernel talk on that page, but
it's a great start for what comes next (actually, 
next I think I'll do a tutorial based on Thin Red Line...
but after that his stuff will come in handy)

Between his feedback and Thomas' help with Thin Red Line,
I definately need to get an acknowledgements section going...

> Thanks again,
> I'm looking forward to the rest of your tutorial.

Hope it lives up to your expectations!

Actually, a general kernel question I've been mulling over:
What's the best way to do missile heights?
Thin Red Line is so simple it never even bothers to turn
off the damn missile. And Ruffin Bailey's "dismiss1" kind 
of punts, it does the two WSYNCs it needs right there, not
going through the rest of the loop. (Which seems to me like 
it would break any other screen items we were having to keep  
track of, at least that might be on the same scanline) 

Is the usual way of doing this something along the lines of: 
(in Pseucode)

IF SCANLINE == VERT POSITION OF MISSILE
  TURN ON MISSILE
  SET REGISTER OR COUNTER TO MISSILE HEIGHT
END IF
IF  MISSILE REGISTER/COUNTER IS ZERO
  TURN OFF MISSILE
END IF
DECREMENT MISSILE REGISTER/COUNTER

Or is there a cleverer (yet not too devious and hard to understand)
method of doing this?

-- 
KirkIsrael@xxxxxxxxxxxxx    http://kisrael.com
1. We are not heroes. 2. Our time here is brief. 3. Our untapped potential 
is limited: We are doing about the best we can do. 4. Personal charm doesn't 
count for much. 5. There's no point in looking back. It doesn't help.
--Jimmy (Big Boy) Valente as told to Garrison Keillor


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