On 5/21/23 13:30, Gonzalo Garramuño wrote:
El 21/5/23 a las 16:07, Manolo escribió:
The example program calls function fl_scale(double x, double y) with null x and y.Correct, as a side effect of not initializing the values.
A scale of 0.0 does sound bad, and I might expect that to
cause a matrix error.
If you just add a check in your code so the x,y scale never
gets below, for example, 0.1,
does that fix the app?
FWIW I was able to get your app to work by adding the above
scale check,
adding colorbar pixels, and drawing dots with
fl_begin_complex_polygon() / fl_circle(),
the attached code gives me:
Pretty close to the old tektronix vectorscopes, but without the NTSC orientations:
I suppose digital vectorscopes don't have to bother with that old
ntsc weirdness, though I thought maybe they'd keep it for consistency (shrug),
with the zero axis being at the far left, representing the "vomit yellow" of
colorburst, and then rotating clockwise through the color circle towards
yellow, red, magenta, etc. This way a grayscale (zero chroma) ended up
as a straight horizontal line going to the left.
I suppose digital vectorscopes don't have to bother with that old
ntsc weirdness, though I thought maybe they'd keep it for consistency (shrug),
with the zero axis being at the far left, representing the "vomit yellow" of
colorburst, and then rotating clockwise through the color circle towards
yellow, red, magenta, etc. This way a grayscale (zero chroma) ended up
as a straight horizontal line going to the left.
Oops, I'm wrong about that last bit with a grayscale; on a
vectorscope a grayscale
would just be a dot at the center, lol.
It was colorburst I was thinking of that marched to
the left on a vector scope,
and they had a special target for it so you wouldn't mistake
it for part of the visible image.
Since all NTSC signals had colorburst in them, even a
completely black image,
it would be seen at all times on a vectorscope as a short line
from the center
off to the left (red circle below).
Colorburst was normally never seen as a color since it was
hidden in horizontal blanking,
but could be made visible in the handy "cross pulse" mode of
most studio monitors:
Burst was an unmistakeable mustard/vomit yellow bar in the
blanking area.