[ColorForth] 25x graphics

[Dave Lowry <lowry@xxxxxxxxxxxxxxxxx>]

On Thu, 13 Dec 2001, John Drake wrote:
 
> The other interesting posibility is 3D video.  
> Some people dismiss MISC chips for 3D video because
> of the lack of a floating point co-processor or
> even a divide instruction.  But after getting more
> information from Jeff's site about the 
> implementation of CORDIC functions on the F21
> I believe that quality realtime 3D graphics is
> possible on the 25x.  I also read that someone
> was working on a 3D graphic wordlist for the F21.
> Did anything ever come of that?
> 

That might have been me.  I did a 3D vector package for P21 using 10.10
fractional fixed point math.  It was modeled on the (old) SGI graphics
libraries and had 3D clipping, etc.

I had filled polygons working, but couldn't progress further because my
Ting P21 board's serial I/O wouldn't stay stable long enough to get all
the words downloaded. :-(

It was a great deal of fun and Jeff was most kind in helping me out with
Forth and P21 Machine Forth.  After working with P21 MF for a while you
kind of develop a sense of "stack rhythm".  That is, you begin to see how
to make the solution match the CPU, and the limitations of stack depth,
etc. aren't such a big deal.  And you begin to see what an elegant,
beautiful thing Chuck has come up with.

But, as Jeff has tried to (gently) tell MF newbies, there's no easy path.
You've got to work with the chips (or simulations) for a while before you
"get it".

-Dave

Not speaking for my employer, etc.


> --- Mark Slicker <maslicke@xxxxxxxxxxx> wrote:
> > I was thinking a bit about how one might implement
> > video using the
> > 25x. The 25x apears powerful enough to eliminate the
> > need for a
> > frame buffer. Some quick calulations will show that
> > a core at 2400 MIPS is
> > capable of updating a screen of 1024x768 pixels at
> > 60 Hz. 18 bits are
> > capable of a respectable number of colors. The
> > parallel architechture
> > should allow for many interesting stratagies for
> > drawing. 
> > 
> > Perhaps someone could tell me this, I don't know
> > much of electronics yet,
> > how would the electrical interface for the video
> > work? I've implemented a
> > VGA video controller once on an FPGA, it was very
> > simple. The vertical and
> > horizontal syncs were generated by counters and
> > additional logic. The
> > colors (RGB) were either on or off for an 8 color
> > display. Every thing 
> > was calculated based off a fixed clock. With this
> > interface, I'd assume
> > you'd need some digital to analog converters, and
> > perhaps something to
> > syncronize everything to get the timing right. Let
> > me know what you know
> > about this, or perhaps point me in the right
> > direction (books, links, 
> > ect).
> > 
> > Mark
> > 
> > 
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