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AmiDog
Registered: Mar 2003
Posts: 97 |
160x100 pixels screenmode
Is it possible to trick the VIC into displaying every line of the bitmap twice, creating a 160x100 pixels screenmode? If this is possible, can it be combined with FLI? |
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Melkor
Account closed
Registered: Apr 2006
Posts: 11 |
I'm no expert but alternating FLI and FLD every other line should do it. |
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Jetboy
Registered: Jul 2006
Posts: 337 |
cant you do simple fli and just double the data?
edit: I mean put the same data for 2 lines? |
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Oswald
Registered: Apr 2002
Posts: 5094 |
you can do it, perhaps not in the way you think about it. You simply draw up the picture in a way that each pixel is doubled vertically. if u're thinking of effects dont expect less writes/pixel than in 160x200... So strictly speaking a software screen mode for this is not possible. (now someone come and proove me wrong I'll be glad:) |
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Jetboy
Registered: Jul 2006
Posts: 337 |
You still need as many STA as you would normaly need, but you you would need jsut half the calculations
... calculations
sta adr
sta adr+1
Plus you can use every second fli routine based on NMI and timers (courtesy of Ninja). That way displaying fli wouldnt cost you 200 lines of rastertime, but just 60% of that. So it is improvement.
Hoever 4 field type, every 4th line Fli is stil more efects friendly.
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Melkor
Account closed
Registered: Apr 2006
Posts: 11 |
I'm pretty sure you can stretch with a variation of FLD but I don't know how it's done exactly. |
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Melkor
Account closed
Registered: Apr 2006
Posts: 11 |
Checked the VIC article and found this:
"If you create a new Bad Line before the current text line has been finished, VCBASE is not incremented (see 3.7.2.). So the VIC reads from the same addresses in the video matrix as in the previous line."
So doing doing FLI two times every other line should give you what you want, without having to plot the whole screen. |
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JackAsser
Registered: Jun 2002
Posts: 2014 |
@Melkor: Sorry but no. What they mean is that when VCBASE isn't incremented the next char row (8 lines) is a copy of the first. If VCBASE IS increased then you get a new char row. The only possible bitmap stretching/line repeating is to repeat line 7 of each char row.
What FLI does is to force a re-fetch of the screen data and the d800 data, not the bitmap data. The bitmap data is incremented anyways and depending on where you put your d011 for FLI you may get the first bitmap row repeated all the time, or you get new ones. |
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WVL
Registered: Mar 2002
Posts: 902 |
you can simply do FLI every 2 lines, instead of every line, and draw the bitmap so the pixels are doubled. i wouldnt do any stretching or whatever unless you really need the memory (also, i don't think it's possible to stretch in such a way..) |
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Radiant
Registered: Sep 2004
Posts: 639 |
...and for a monochrome 160x100 pixels mode you can of course just multiplex hires sprites over the screen. |
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MRT
Account closed
Registered: Sep 2005
Posts: 149 |
Quote: ...and for a monochrome 160x100 pixels mode you can of course just multiplex hires sprites over the screen.
Ehr yeah, but why would you?
Then it would be easier to make just a simple monochrome bitmap, don't you think?
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