SpiceWare's Blog - Stay Frosty, Part 10

RSS Bot · December 14, 2018

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

Missile 0 Stars (orange)

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)

Star Test ROMs:

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)

Besides that I revamped the controls to use left-right and fire for jump, as well as added preliminary inertia.

ROMs:

Source:

Blog entry covers November 23, 2007

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