> Yeah. BTW, why real sprites are so scarcely used on and beyond MSX2? If
> Spectrum users were given a single sprite...
>
> Sprites usually have serious limitations in all computers with built-in
> sprite circuitry, but there're means to overcome them (at least to some
> extent, look Shadow of the Beast and Turrican on Amiga) but I keep coming
> across bitmap-only *JERKY* moving objects which give games an early 90s
> PC-wise look & feel.
>
> There's a game which even lists the lack of sprites as a feature!!!
>
> IMO wiser use of sprites and MSX-only features (like the KEWL multicolor
> mode!!) would render more MSX-styled games.
Yeah! If you use 4 'sprites' per sprite (if you get what I mean), then you
can use full-color graphics! Too bad you can only have 2 of 'em on one line.
Anyways, there are also some disadvantages, what about slowing down the
copies with about 20%???
Take a look at this... This is a part of an article I have written for
Track, and later for XSW-Magazine. Although it isn't complete (I should have
tested HMMY too), the numbers are VERY accurate, and can very well be used
to check is an idea is realizable on the MSX.
For instance, when making a full-screen horizontal scroll (with screensplit,
so not really full-screen) you'll have to make copies of 16x160 pixels per
interrupt, in screen 5 that is 1280 bytes, which is therefor fast enough for
the v9938 can copy about 2700 bytes per interrupt.
==============================
Hightly simplified extraction from the article in XSW-Magazine (Dutch)
written by me.
==============================
(some explanation)
First, there is the official name of the tested VDP-command. Accuracy is the
accuracy of the speed. If the accuracy is 32 and the speed is 3552, the REAL
speed can vary from 3552 to 2583. But this you can forget that, it's just
for the completeness.
Spr means sprites, which can be en- or disabled (bit 1 of VDP r#1).
Lin means the nr. of lines which are displayed on the screen, 212 or 192
(bit 7 of VDP r#9).
--Blank-- means that the entire screen is disabled (bit ? or VDP r#?).
Next, speed. This number indicates how many bytes the VDP can copy per
interrupt, or, in the case of LMMV and HMMV, can fill with a certain color.
These values go for ALL screens of 5 to 12 (exept for the Korean textscreen
9 ofcourse).
Finally, 50/60 Herts. This belongs to Speed. The left value of Speed
indicates the nr. of bytes per interrupt at 50Hz, the right value the nr. of
bytes per 60Hz-interrupt.
== The Copy-commands =====================
LMMM accuracy: 16 HMMM accuracy: 32
Spr / Lin - Speed 50/60Hz Spr / Lin - Speed 50/60Hz
on / 212 - 1232 / 976 on / 212 - 3552 / 2784
on / 192 - 1264 / 1008 on / 192 - 3616 / 2880
off / 212 - 1584 / 1312 off / 212 - 4384 / 3616
off / 192 - 1584 / 1312 off / 192 - 4384 / 3684
--Blank-- - 1600 / 1344 --Blank-- - 4512 / 3776
Some remarks:
- First, a High-speed Copy (HMMM) is a little more than 2.8, thus almost 3
times, times as fast as a Low-speed Copy (LMMM).
- Did you notice that disabling the sprites when giving a Copy-command
matters very much??? If the speed gained by disabling of the screen is
indicated with 100%, then only the disabling of the sprites already gives
87% of these 100%!!! So only disabling the sprites gives almost as much gain
in speed as disabling the whole screen!
In case of a copy it doesn't really matter if you set the screen to 212 or
192 lines.
== The Fill-commands =====================
LMMV accuracy: 16 HMMV accuracy: 64
Spr / Lin - Speed 50/60Hz Spr / Lin - Speed 50/60Hz
on / 212 - 1696 / 1344 on / 212 - 7040 / 5632
on / 192 - 1728 / 1392 on / 192 - 7168 / 5760
off / 212 - 1840 / 1392 off / 212 - 7232 / 5888
off / 192 - 1856 / 1504 off / 192 - 7360 / 5952
--Blank-- - 2128 / 1776 --Blank-- - 8448 / 7040
Some remarks:
- Whow!!! A High-speed Fill is FOUR TIMES AS FAST as a Low-speed Fill!!!
- Here the switching of the screen to 192 lines DOES matter a little. If the
speed gained by disabling the sprites is indicated with 100%, then disabling
the lower 20 lines gives a gain in speed of another 66%... However, in
reality the gain in speed ain't that much, for the disabling of the lower 20
lines and the sprites only gains 320 bytes on 7040 bytes; only a gain of
0,05%.
~Grauw
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