atarionline.pl New Graphics mode - 159x192 Graphics 10+15 - Forum Atarum

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2. Grafika / Graphics  »   New Graphics mode - 159x192 Graphics 10+15

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    I was reading a thread on AtariAge about using APAC mode, but in Graphics 15 to get 16 colors at 160x96 (4 chroma x 4 luma) ... thread is here:

    ->link<-

    Popmilo let me have a look at his code, and I modified it a bit, to change between Graphics 15 and Graphics 10 every scanline, and also to shift the screen up and down by one scanline every VBLANK ...

    It looks like we have a new Graphics mode, 159 x 192 pixels, 30 colors, without flicker, and only using 8k memory. What is essenntially happening is a vertical version of the HIP effect ... you have 160x96 in mode 15, and 80x96 in mode 10, which is shifted down a scanline every VBLANK. Because there are no blank lines in this mode, each scanline interlaces with the next, and you have a solid image.

    To set it up, you do scanline changes from mode E to mode F, set the GTIA to graphics 10 on the mode F lines, and alternate COLBAK between the background color (in mode E) to the 9th color (in mode F). Then you alter the first instruction of the DLIST between 112 and 96 (skip 8 scanlines to skip 7) to shift the screen up and down.


    I used graphics 15+10, but it is also possible to use other combinations, I think ... like 15+9, 8+15, and even 9+10 ... maybe getting HIP pictures that only need 8k. Maybe these can be used in actual games?

    I have attached four executables. A converted picture of obi-wan, a converted picture of Mr. Spock, and two converted screen captures from games.

    If you view these in Altirra, use frame blending, and PAL or NTSC no artifacting. Would love to hear how these look on real hardware.
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    A palette test, showing all 30 colors in one scanline.

    There are actually 9 color groups of 4 colors, but in the background and PF0-PF2 color groups, some of these are repeated.

    It is possible to reduce flicker when using solid fields of PF0-PF1-PF2-BAK colors, by doing a dither pattern ...

    For instance:

    Mode 15: PF0|PF0|PF2|PF2
    Mode 10: PF2 | PF0
    Mode 15: PF0|PF0|PF2|PF2
    Mode 10: PF2 | PF0

    This produces the same color, but blends the colors on alternate frames, and reducing the flicker.
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    An attempt to do a Commodore 64 picture

    Not entirely accurate, but this is due to limitations in the Graphics 10 converter. A bitmap editor in this mode would likely improve the color quality.

    Also on this post is the original C-64 image for comparison
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    Today ... a picture in HIP mode, using this method. We can now do HIP pictures in only 8K. I've attached here, an 8K HIP render of a screen capture from the PlayStation game "Escape Plan", and also a 16K double-laced HIP. The 8K only looks a little bit fuzzier.

    Maybe possible now to use HIP mode for games? Something like Escape Plan is certainly possible, as it would only require some softsprite movement or animations of objects like doors and platforms.

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