From: Hatch (hatch_at_in.com.au)
Date: 2004-10-31 21:46:26
----- Original Message -----
From: "Christopher Phillips" <shrydar@jaruth.com>
To: <cbm-hackers@ling.gu.se>
Sent: Sunday, October 31, 2004 11:35 PM
Subject: Re: C64 GRAPHICS CARD
>
> On 31 Oct 2004, at 18:45, Hatch wrote:
>
> > Now that I have almost finished the semester I would like to look at
> > interfacing my cct to the C64,
>
> Uh-oh, here comes another C-1 ;-) ;-)
>
No, this is going to be just a SIMPLE card for to C64 itself.
I must stress that the specs are going to be very low.
> >
> > One thing I would like to do when I redesign the cct is to give it a
> > way to address graphics data so that 3D graphics can be calculated
> > quicker (basically something other the 8x8 cells) either 200 rows of
> > 40 bytes (horizontally formatted) or 40 columns of 200 bytes
> > (vertically formatted). This way my cct will be useful for something.
> > At the Moment I'm leaning towards horizontal formatting (but it's a
> > question of which ever way is faster for calculating 3D graphics
> > with).
>
> For plotting 3d graphics in software on 6502, I'd lean towards vertical
> formatting - that way you can do a single routine for xor-filling
> across a line, which you can index your stores in order to select the
> pixel row you are writing to. That's assuming you're using c64 memory.
I'm thinking that EOR filling will be done by the cct, as the ctt displays
the
image it EOR fills (takes up no CPU cycles, this was the idea of someone
on the CSDb forum), there will be a control bit that turn EOR fill on or off
and 40 addressable bytes for setting the initial byte to EOR with at the
start
of each column and then stores the result ready for the next row. . With
this in mind would horizontal formatting be faster for the 3D calculations?
>
> OTOH, if you use external memory and have a c64 mapped IO register that
> writes to an auto-incrementing location in VRAM, then horizontal
> ordering would be better.
>
> Of course, you could get better performance if your hardware did some
> of the 3d work itself, but that's a much harder problem :)
>
This would be ideal (cct doing some of the 3d work itself), if I use C64
memory I would like to at least use the idol video accesses (When the
raster is outside of the display window) for clearing or byte filling
memory.
Although this isn't 3D work it would clear or fill a portion of memory
without using CPU cycles which would have to speed things up.
Are you thinking that the cct could actually do some calculations and
return values to the coder?
> Good luck!
> Christopher.
>
Thanks.
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