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First post, by unknownuser

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Newbie

ok, i tried it myself for weeks now and maybe it is really easy for someone and i'm just too stupid....

the problem is the following: i wanna make an intro-animation like id did it with commander keen 4-6 (the scrolling letters which will be highlighted when they overlap). however all i try is a) slow b) doesnt work or c) the 64k of video-memory arent enough 🙁

does someone know how this is done in commander keen? or is there any program where i can dump the entiry video-memory?

or can i copy from plain x1 in vid-mem x2 to plain y1 in vid-mem y2 in write mode 1?

some infos: ck uses ega-mode 0x0D, the letters KEEN appear in plain 0, the letters COMMANDER appear in plain 1, the palette is changed, so that color 1 and 2 are a dark grey and color 3 is a light grey (if keen and commander overlap, the resulting color is 3). CK uses pixel-panning during this animation (i think for scrolling through COMMANDER so that they only need one shift - but than i need 8 shifts!!! for KEEN).

i dont know where to post this things but i thought a forum for dos-emulation *could* be right 😀

thanx in advance

Reply 1 of 2, by Harekiet

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Rank DOSBox Author
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DOSBox Author

As far as i know commander keen just uses some dual screen approach with 1 screen being displayed and the othter being updated with just changing all the screen data that has been changed with a little help for the pixel panning to reduce the changes having to be written.

Reply 2 of 2, by Guest

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The technique is basically to either XOR, OR or AND data together
then set your pallete to the correct colours ..
The effect is known as "Glenzing" (with polygons) and you should be
able to find plenty of old demos that show how it looks and a few with source.

Hint: if you XOR 2 pages before every write; the first will "set" the first
page on the second, the second will remove it again.