Re: [stella] Collaboration

Subject: Re: [stella] Collaboration
From: Thomas Jentzsch <tjentzsch@xxxxxx>
Date: Mon, 13 Jan 2003 09:32:23 +0100
Glenn wrote:
> Let's modify the requirements a bit, or maybe debate them some to come up 
> with a final featureset for the kernel (rubbing hands together with glee).

Go on! :-)

> Although it looks like the ultimate ideal of full 1-scanline res movement 
> accuracy on all object IS doable, it's at the cost of an opaque HMOVE comb 
> on the left hand side of the screen.  I was originally thinking that this 
> would only have to be every other line (which would allow the sprites 
> underneath to show up enough to allow them to move around in that 
> area).  Maybe that's impossible even when interlacing the missile updates?

Since there is no VDEL for the missiles, I have to do the HMOVE exactly in sync with the missile pattern. With flickering missiles you still would get up and down jittering HMOVE blanks, which IMO would look quite bad.

Hm, maybe by replacing one missile with the ball (using VDELBL)? Must think about that....

> Assuming that's necessary, the safe zone can't really extend completely to 
> the left and I really have to constrain the zombies to the 
> 2-playfield--pixel strip on either end (that I see you've widened, probably 
> thinking the same thing I am.)  So for the sake of symmetry, we don't need 
> the zombies to be able to go to the far right of the screen either.  Maybe 
> that makes the timing a little easier??  Marginally?

Well, I get 8 more pixel (or 2..3 more cycles) flexibility. And every single cycle helps. ;-)

> Also, is there a way we can wrap the cars horizontally so they emerge bit 
> by bit from the right hand side of the screen (like a vertical letterboxing 
> effect)?  The left would be taken care of by virtue of the HMOVE comb, but 
> the right would naturally pop.

Hm, I thought the cars can't move into the safe zone. :confused:

Ok, with the current HMOVE comb they can disappear smoothly on both sides because when they wrap around on the right side they will be also hidden under the blanks. But obviously they will be visible a bit further to the right than to the left.

> If the zombies only needed even/odd scanline positioning ala Super 
> Challenge Football, what would that open up?

Only a very few cycles (one HMOVE and both HMCLRs would go -> 9 cycles). And of course only one kernel needed then.

> Also what are the chances of using the ball anywhere in the active part of 
> the screen, assuming that all we may need is a single scanline brick shape?

- with the current setup, the chances are very, very little (IMO *no* way!). 
- with the Super Challenge Football setup, maybe (but IMO probably not).
- with only one missile/screen, yes. 

> If the number of sub-kernels you had to do was doubled maybe you could 
> hardcode all the ball position and width writes so that the Super Death 
> Chase ghost could fade in and out and maybe shuffle left and right but not 
> move vertically.  It could then be a Wizard of War Wizard sort of character.

Hm, that would require double or tripple kernels. One above the ghost (that might be reused below) and one (very large if hardcoded) for the ghost.

> Also, how hard would it be to pull a Gunfight trick and make the zombie 
> colors independent of the cars?  

I think the best idea would be to mix the car colors. Then both zombies have the same mixed color (like the helicopter in Robot City). If both car colors have about the same brightness, this won't be noticable.

When using the ball we are limited to the playfield color, but we could use that for zombie color mixing too.

> The only thing I might want from this is to be able 
> to do the Super Death Chase ghost, which should be white, not 
> red or green.  I could make it green and deliberately flicker it to black, 
> I guess.  The cool thing about that is I could flicker the green missile 
> and flicker the other missile back and forth to generate red eyes.

The only colors we have are the car and the playfield (= ball!) colors. Therefore the ghost can't have an independent color without adding (color) flicker to one of these objects.

> That doesn't sound like too terrible a limitation although it will make my 
> shapes for skeletons impossible.  If I just do these generic guys and 
> nothing else, I'll be more than happy.

Well, you know, I'd still prefer skeletons or zombies. ;-)

> I'm encouraged all right.  You ARE going to go ahead and finish the kernel, 
> right?  

Now that I'm sure about your engagement, yes of course. :-)

> How much time did you spend on this?  You did it so fast!

A few hours during Sunday. I had to find and reread the old threads about DD and then it was quite "easy" to put everything together. But beware, this kernel is still very preliminary, I guess fine tuning it will require a lot more of time.

> If you get the "hard" stuff done...

"When", not "If". ;-)


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