# Creating pixel art

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the brightest colors of the brown ramps look like the yellow group
the second color is orange group vs red group

the two yellows are very little different
subtle slides within a group are possible and then there are dead zones between the groups
the category I mean is the nanometers

damn the bright colors looked like in the yellow group
next to each other they looked like maybe a new hint to do msx1 color 11 vs color 10
then I try them in the msx1 palette and they go orange whoops

I’ve been wondering what the exact MSX pixel aspect ratios (PAR) are. This is relevant when drawing graphics on PC since they have square (1:1) pixels while the MSX doesn’t.

The V9938 vertical display area at 60 Hz is 243 lines, at 50 Hz it is 294 lines. The horizontal display area including borders is 1139 cycles, or 284,75 pixels (/4) in screen modes other than 3, 6 and 7.

As far as I know the display aspect ratio (DAR) of a TV is calculated based on the full frame output including overscan (borders), so we can derive the pixel aspect ratios from these numbers.

The pixel aspect ratios on a 4:3 display are (4y / 3x):

60 Hz: 1296 / 1139 = 1,138 = ~9:8
50 Hz: 1568 / 1139 = 1,377 = ~7:5

The pixel aspect ratios on a 16:9 display are (16y / 9x):

60 Hz: 1728 / 1139 = 1,517 = ~3:2
50 Hz: 6272 / 3417 = 1,836 = ~11:6

In openMSX these would correspond to horizontal_stretch values of 281 (60 Hz 4:3), 232 (50 Hz 4:3), 211 (60 Hz 16:9) and 174 (50 Hz 16:9). Unfortunately only one of these can actually be entered because the values can not be <256. The default is 280 though, so quite correct for a 60 Hz MSX.

Doing the same math for the V9990 B2 overscan mode (384x240 at 60 Hz, 384x290 at 50 Hz)…

The pixel aspect ratios on a 4:3 display are (4y / 3x):

60 Hz: 960 / 1152 = 0,833 = 5:6
50 Hz: 1160 / 1152 = 1,007 = ~1:1

The pixel aspect ratios on a 16:9 display are (16y / 9x):

60 Hz: 3840 / 3456 = 1,111 = 10:9
50 Hz: 4640 / 3456 = 1,343 = ~4:3

Because of the narrower pixels, looks to be a nice mode for widescreen, the PAR is almost the same as a 256-pixel screen mode in 4:3.

None of the MSX video chips were ever targeted for 16:9 displays. Why even take it into account?

I got a sighting, PAL MSX display area fits precisely (plusminus some pixels) on a 16:9 TV.
In the "letterbox1" setting. The 4:3 pic gets zoomed to full width and top and bottom border disappear.

256*h/192*v = 16:9
h/v = 16/9/256*192 = 1,33

Get with the times, Manuel! Bigger screen. No letterbox. Most people’s TVs are widescreen. I’m entertaining the thought, might be nice for something. For 3D it’d be an easy projection matrix change. If someone makes a widescreen game, I will be the last to protest. I think it’d be fun.

(Not saying that I’m going to make 16:9 content, but to say “why even take it into account”… it’s not a ridiculous idea. Either way if I’m going to list aspect ratios, I think it makes sense to also list them for the most ubiquitous display aspect ratio out there nowadays.)

75P PAL on flat TV. when I make the circle command with 1.33 it is round.
then I take the letterbox1 setting. that does not change aspect ratio, the circle is round.
it zooms the 4:3 pic so it horizontaly fits fullscreen on 16:9
and then at the top and the bottom something got to disappear and accidentaly it precisely snips the MSX border
PERFECT

the left char is missing. that can happen, no news versus 4:3 analog TV
and right border is shown ~1 pixel

but the top row is missing ~3 pixels, that's news.
and bottom border is shown ~3 pixels.
dont put the points in the top row.

so, the funny thing is, MSX chips knew nothing about 16:9,
but acidentaly the PAL 256x192 display area always has been a 16:9 box

the aspect ratio is an ungoogleable topic. in a old book about analog TV I found:
585 of 625 lines
52 us of 64 us
that is the maximum display area, the rest of the time is sync

calculating the MSX pixels:
the MSX has 342 pixels per line.
52/64 * 342 pixels = 277,8 pixels in TV display area
585 lines / 2 = 292,5 lines in a 20ms frame
277,8 * w / 292,5 = 4 : 3
w = 4 / 3 / 277,8 * 292,5 = 1,403 PAL MSX aspect ratio

a sighting: the 75P manual of CIRCLE too says 1.4

if one would take 64us, 625 lines to calculate it then one would end up with a different ratio!
the total timings have a different ratio than the display area
because horizontal blank is more problematic and so snips more percent off the usable display

aaah and with a NTSC machine put the TV to "enforce 16:9" horizontal stretch
the result again is 256x192 pixels on 16:9
no new aspect ratio but rather things converged, nice
PAL MSX: TV in letterbox mode
NTSC MSX: TV in 16:9 mode

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