From: Ben Larson <wazzapfool@xxxxxxxxx>
>
> My first idea involves sort of a combat remake, except
> have the board rotate around the tank. Not sure how
> good this would look, though, assuming playfield
> graphics were actually used for the playfield...
Check the archive for my Cartesian to Polar Conversion demo.
It implements the basic math you need for the rotations, but as
you can see the linear motion is pretty jumpy. I've figured out
this is due to using 1.4 degree increments (1/255 circle) for
the basic angular unit. It should be possible to redo this using
0.35 degree increments without using much more table in ROM,
but angles will then be 10 bit and it may take more logarithm
table to do the scaling multiplications. I'm not sure how well
it would fit in 4K, though it might be OK for a paged cart.
One of these days I may get back to doing that, but for now
I'm thinking about algorithms for generating the display.
If I come up with a workable kernal, I may return to the
rotation-positioning problem.
Using the playfield won't work. You don't have enough
CPU cycles _or_ RAM, and it would look crappy at 40
pixels horizontal resolution even if you did.
> My second idea is for a platform Super-Mario-type
> game, using the same scrolling effect that Thomas used
> in Thrust. Maybe even recycling some of that kernel
> (?). :)
Thomas already explained why the Thrust kernel won't
translate. Doing much of any kind of action in combination
with an asymmetric playfield is a real PITA, as you spend
about half the kernal cycles on *every single line* just
keeping the playfield updated. It might work as a vertical
scroller, though, with a symmetric playfield.
> Kind of grandiose, I know...but not as
> grandiose as my third idea, which is for an RPG a la
> Legend of Zelda or Final Fantasy. Using a smart
> flicker algorithm, it should be possible to have 8
> player objects on-screen at once (right?), which would
> be enough for enemies and the hero. I think the
> hardest challenge would actually be creating the rest
> of the screen...presumably using the playfield,
> background, and missiles...
You cannot horizontally scroll the playfield in a way that
will look anything but awful. And you will use a
boatload of ROL/ROR's and RAM as well as the
whole asymmetric playfield problem mentioned before.
Again, you might be able to do something that
scrolls vertically and pages horizontally. If you want
horizontal scrolling, my advice is to forget the playfield
entirely, unless you are using it for something *really*
simple and coarse, e.g. one wall with one hole per screen.
OTOH I once saw an ad for DOOM for the 2600, so
I guess anything is possible... *
--Roger Williams
* It was a hoax.
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