[stella] Visual questions
Subject: [stella] Visual questions|
From: Glenn Saunders <cybpunks@xxxxxxxxxxxxx>
Date: Tue, 25 Jul 2000 04:00:17 -0700
Two visual-related questions.
When talking about a byte, the numbering is like this, right?
128 64 32 16 8 4 2 1
What about the bit numbering? Does it go from left to right or right to left?
The memory map diagrams and everything else indicate bit0, bit1, bit2,
bit3, etc... The actual location of the bits address numbers is important
in visually representing the memory map, since many registers have special
values in individual bits or pairs of bits.
So when drawing player sprites for use in memory by using graph paper, what
you see is what you get on the screen if you feed it numbers like the
X X X X X X X X = 255
X 0 0 0 0 0 0 0 = 128
X 0 0 0 0 0 X 0 = 130
Also, how I'm going to explain VDEL is that it has the net effect of
shifting sprites down a single scanline. So if you want to move a sprite
up a single scanline, you move it up a full scanline (since it's a 2 line
kernel) and enable VDEL, the next frame you don't enable VDEL so it has the
effect of moving it another single scanline, and so on.
If you want to move a sprite down a single scanline, just position the
sprite at the same place and enable VDEL. If you want to move it down two
scanlines, then move it to the next line in your two line kernel and don't
Also, I've noticed that a lot of source code stores sprite data upside
down. Any reason why? Do they scan memory by decrementing a counter or
Glenn Saunders - Producer - Cyberpunks Entertainment
Personal homepage: http://www.geocities.com/Hollywood/1698
Cyberpunks Entertainment: http://cyberpunks.uni.cc
Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/
Steve . Porter - Mon, 24 Jul 2000 22:59:16 -0400 (EDT)
Thomas Jentzsch - Tue, 25 Jul 2000 03:45:35 -0400 (EDT)
- Glenn Saunders - Tue, 25 Jul 2000 07:02:08 -0400 (EDT) <=