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tonysavon
Registered: Apr 2014
Posts: 25 |
Different side border colors
I'm trying to obtain (what I thought was) a very simple effect. While displaying a bitmap, I need the side borders to be of different colors just for the 200 lines visible part of the screen (so top and bottom borders would be black). Say I want the left border to be white and the right border to be red.
I played a bit with timing and I kinda achieved something, but it's not really working very well yet. I was wondering if there was a pre-made piece of code somewhere for doing this kind of vertical splits, possibly with a LUT, so that I could have 200 different colors on the left and 200 different colors on the right. Right now I feel like if I keep hammering this spaghetti mess I have in front of me I'll eventually manage to do something, but I wouldn't want to re-invent the wheel and I'm sure there's a clean, short way of doing this
Thanks |
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MagerValp
Registered: Dec 2001
Posts: 1078 |
It's one of those problems that seem simple, but are in fact tricker than you expect. Due to badline DMA you can't change the border color while the screen is being displayed, and the first write cycle is available too late:
https://www.dropbox.com/s/wzac1xmjy6iy2w2/lrborder.png |
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Dr.Science
Registered: Oct 2011
Posts: 41 |
In one of my last intros, I use different border colors. As it was only for a small area, the timing was done "by hand" for each rasterline: PETSCII Intro |
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ciccior2003
Registered: Jun 2012
Posts: 13 |
Shifting on the right the bitmap ( $D016 $0F ) you can put 2 sprites on the left one on the right to cover all the borders. So you have an other sprite to cover one side border with a new color. |
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tonysavon
Registered: Apr 2014
Posts: 25 |
Dr.Science, this is exactly the kind of effect I'm trying to obtain. It was very silly of me not to think your intro, since I've been staring at that petscii quite a bit when it came out.
Indeed, the current version of my attempt is exactly what you have done there: manual timing line by line for a small portion of the screen. Although your code looks way more polished :-P.
I think it must be possible to have it for generally long areas and with a LUT to change the colors at will, but perhaps I'm wrong. I'll keep researching and I'll post my findings if I ever land somewhere.
Thanks everybody for your support :-) |
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Oswald
Registered: Apr 2002
Posts: 5094 |
cpu is too slow for LUT based timing on this IMHO.
here's a pointer: try to make it work for one character (8 lines including bad line on top)
then it should be possible to repeat this code (macro or copy paste) for every char row. |
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Mantiz
Account closed
Registered: Apr 2006
Posts: 36 |
You can do as above and load the colors directly from a color table somewhere in memory without indexing. Instead you manipulate the color table in the bottom and top border.
For 200 lines it will be 400 bytes at most to change, for which enough cpu time should be available in the top/bottom borders.
(unless the music takes too much time or you are doing something spectacular, then you have to do some of the manipulating during the rasterlines instead, or place some color data in ZP to save cycles.) |
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Flavioweb
Registered: Nov 2011
Posts: 463 |
As Oswald stated, is possible to do this with a loop, or a macro, but timing should be "hand-made" for each "text" line:
https://dl.dropboxusercontent.com/u/93655104/border-poc.jpg
Colors may be loaded from a table... |
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Trurl
Registered: Mar 2002
Posts: 61 |
Another example: Mietaa |
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MagerValp
Registered: Dec 2001
Posts: 1078 |
Hmm, what am I missing in my test code? Ah, have to use an rmw op (e.g. sta $d020,x) to get it to write at the right cycle. Silly me. This works of course:
.macro delay
ldx #9
: dex
bne :-
bit $ea
.endmacro
lda #left
sta $d020
nop
nop
bit $ea
lda #right
sta $d020,x
lda #left
sta $d020,x
delay
lda #right
sta $d020,x
lda #left
sta $d020,x
delay
lda #right
sta $d020,x
lda #left
sta $d020,x
delay
lda #right
sta $d020,x
lda #left
sta $d020,x
delay
lda #right
sta $d020,x
lda #left
sta $d020,x
delay
lda #right
sta $d020,x
lda #left
sta $d020,x
delay
lda #right
sta $d020,x
lda #left
sta $d020,x
delay
lda #right
sta $d020,x |
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The Phantom
Registered: Jan 2004
Posts: 360 |
It can be a pain in the butt, for sure.
You can also see it here... Nightmare Intro
The code for the lower splits is somewhere around $5000... |
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