RE: Frame complexity

> I'm trying to get a handle on just how far I can push the drawing
capabilities of my G05-802 monitor.
> Is there some sort of example out there, game or otherwise, of the largest
number of lines I could get
> away with per frame? I know that it's a limitation of the monitor itself,
not the software; it's just hard
> for me to grasp what I can actually get away with. Imagine if I were to
just draw lines randomly from
> one edge to another, how many of those lines could I draw per frame? What
happens if I just keep
> drawing lines and never refresh the screen?
 
It depends on the type of vector generator and what sort of frame rate you
want to achieve but if, for example, you want to do 60fps (which would be
quite high for a vector game) that works out to about 16.66ms per 'frame'.
A ZVG on the G05 setting will draw at about 15us per inch. If you were to
consider all 'movement' of the beam to be drawing time (ie, no high speed
'jumps' to a new position while the beam is off) you could do something like
16.66ms / 15us = 1111 inches per frame.
 
If the monitor is roughly 19" diagonal and a 4:3 aspect ratio, it's about
15" wide and 11.25" tall. So, dividing 1111 by 15" you get about 74 full
length lines running the width of the screen. (Practically speaking these
will all be "approximately"-- so for compatibility I wouldn't plan on
pushing things right up to the theoretical limits to be safe...)
 
Most vector games run slower than 60Hz though. At, say, 30Hz-- that
number's more like 148 lines, etc.
 
The G05 can 'jump' faster than the vector generator will normally draw, so
practically speaking "black" (moves) can be faster than "white" (draws)
which saves you some vector time.
 
If you keep drawing lines (but never 'redraw' then in them same place) it's
about like an analog oscilloscope -- they just fade away. You need to
redraw all the lines every ~1/30th of a second or so for a stable image.
(ie, refresh the screen) There's really no fixed frame rate on the vector
display. It can vary depending on what's going on, so like in ESB it can
get flickery and start looking a tad bit like a slide show and the frame
rate drops. For 'easy' and to keep things consistent you can have the
vector generator triggered with 'fixed' frame rate and then just be sure
that what you're telling it to draw fits in the time allotted.
 
If you have a fixed 'frame' rate that tells the VG to start drawing at a
particular interval always and it's not done drawing the previous frame of
data, you'll just "lose" things on the screen. Similarly, if you try to
jump the beam too fast and don't allow enough settling time, you can get
vectors that 'curl' because the brightness is turned on before the coils
really had a chance to deflection the beam to the final destination. (You
see that if you try to run Star Trek on a stock WG6100 for example-- or even
my Sega Multigame menu 'arrow' would do that too.)
 
You need to keep in mind as well that the spot killer can activate if
there's not enough deflection around the screen. In Vector Breakout I
actually draw a big box around the entire playfield (a couple of times,
IIRC) because the spot killer was activating otherwise-- presumably because
the display is rather 'top heavy' with all the bricks on one side and then
only the paddle and a couple other elements down low.
 
One other thing to mention... On the color monitors the dark glass in front
of the CRT makes a HUGE difference in reducing visible frame rate flicker.
I was a little freaked out when working on Vector Breakout because if seemed
quite flickery to me on a bare CRT, but with the glass in front I'd say 90%
of the effect totally disappeared.
 
-Clay
 

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Received on Mon May 21 16:32:18 2012