Author Topic: 3MODE  (Read 535 times)

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Offline ComSoft6128

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3MODE
« on: 16:38, 10 June 21 »
One screen/three modes

1986 program by Petrel Informatique.
The two BASIC files are Listed in the video.


https://www.youtube.com/watch?v=Bfx_cCeZyfI

Links:
https://www.cpc-power.com/index.php?page=detail&num=16687

https://cpcrulez.fr/info-petrel.htm


Not  emulated - original hardware and software.

Please note that  the aspect ratio for this YouTube video is 16:9 but the CPC monitor
has an aspect ratio of 4:3 so you may wish to adjust your viewing device accordingly.
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Offline Gryzor

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Re: 3MODE
« Reply #1 on: 17:00, 10 June 21 »
*magic*!

Well, it'd have looked like it to my eyes back in '86...
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Offline ComSoft6128

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Re: 3MODE
« Reply #2 on: 17:06, 10 June 21 »
Same here
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Offline eto

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Re: 3MODE
« Reply #3 on: 22:20, 10 June 21 »
Pretty clever !
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Offline ComSoft6128

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Re: 3MODE
« Reply #4 on: 08:19, 11 June 21 »
I imagine the answer to how this was done is in the .BIN file but the way the effect is achieved is beyond me.
Can anyone explain?
« Last Edit: 08:39, 11 June 21 by ComSoft6128 »
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Offline Kris

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Re: 3MODE
« Reply #5 on: 08:51, 11 June 21 »
It uses the fast interrupt of the CPC: when synchronized with the CRTC refresh rate @50Hz, it occurs 6 times per screen refresh (fast interrupt is performed every 1/300th second) so that you can define area and change mode very quickly at the line you want.
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Offline eto

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Re: 3MODE
« Reply #6 on: 13:27, 11 June 21 »
so that you can define area and change mode very quickly at the line you want.

The |3mode command is probably doing this. The (imho) clever part is the |Defmo command. I haven't checked the BIN but from the BASIC program, I would expects, that this command tells Basic which Mode is selected, then the program is drawing in an area which is set to this Mode. This makes sure that drawing graphics or text it doesn't create garbage on screen.
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