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Stay Frosty, Part 10

Posted by SpiceWare, in Stay Frosty 14 December 2018 · 369 views

Last time around, while visiting family for Thanksgiving, I'd implemented a preliminary starfield. I'd originally tried doing so using missile 1, but it didn't work (in Stella) so I changed it to use missile 0. In and of itself that was fine, but missile 0 was used for the melt trail so needed to be repositioned after displaying the stars. As a quick workaround I just added 2 extra scanlines to reposition missile 0, which had bumped the scanline count from 262 to 264.


Stella Debug Colors
Attached Image



Missile 0 Stars (orange)
Attached Image

When I posted about the stars, batari came back with:

We tried the starfield trick last year and the emulation is very inaccurate. Stella is only designed to emulate the exact conditions from Cosmic Ark, not the general starfield trick.

 So I changed it over to use the ball and removed the missile 0 reposition. (Stella's been greatly enhanced since then and now accurately emulates the starfield trick with all objects).


Ball stars(light blue)
Attached Image

Star Test ROMs:
Attached File  frostyStarTestNTSC.bin (8KB)
downloads: 41
Attached File  frostyStarTestPAL.bin (8KB)
downloads: 40
That worked, though Albert replied back with:

I just tested it on a four switch with a Commodore 1702 monitor and it matches your screenshot but it's very flickery, so much so that it's distracting.

 I agreed, the problem was in order to draw enough stars I was having to flicker them at 15 Hz. After further discussion I ended up reverting to my original implementation that used missile 1, reduced flicker to 30 Hz, then used 2-copies-wide on one frame and 2-copies-medium on the other to add additional stars. Alternating copies between wide and medium solved a problem with the stars being too repetitive in their layout.


Missile 1 Stars (green)
Attached Image

Besides that I revamped the controls to use left-right and fire for jump, as well as added preliminary inertia.
Attached File  frosty071123NTSC.bin (8KB)
downloads: 43
Attached File  frosty071123PAL.bin (8KB)
downloads: 42
Attached File  sf_source071123.zip (53.27KB)
downloads: 42
Blog entry covers November 23, 2007

Nice to see you resuming this series. :)

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