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Coco3 hardware scrolling from Basic !


MrDave

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Yes i converted a bmp image into 8k chunks and load them in the ram. With loadm "plata...platb etc

Then from basic i set variable vv to the start of my image in ram and poked that to the video chip,.. then i scroll down a bunch of times by adding 32 to it.. then i use to joystic to adjust the pos.. i have a dsk image if you want

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  • 1 year later...

MrDave - Sorry to bring up this necrothread... But did you ever upload the code to the archive? I've got somebody asking me about it, did I get it to run, etc - and I never played around with it further to try to load my own image or something. I tried to run it in xroar online by skipping the disk load (ie 5 GOTO 60) - but it appears to lock up the emulator (I'm not sure if xroar is set to 512K which the code would have to use, right?). I haven't tried any other emulator, or a real machine, yet...thanks...

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Sorry i had forgotten about this... i went back to machine language lol ..i think someone posted it to the archive as i had put up the dsk image on the coco discord.

. Like most of my demo's i am just quickly showing what can be done..

I used paint shop to convert a bmp image to 16 colors and 256 bytes wide ( 512 ) then chopped up the image file into 8k chunks to put into coco ram from basic..

Then from basic you just have to tell the gime chip where to start in ram and you can move around your image from hardware.

To convert a image to work on the coco you need to have a bmp the screen width  usually 320 but this case it 512.. save the image upsidedown ( thats how bmp files are ) then you can get the raw data ( remove the bmp header 114 bytes  if i recall correctly )

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Another trick that would work with this is my sub sprites ( compiled sprites ) from basic... the sprites are a self contained ml sunroutine that draw themselves to wherever you point.. lighting fast even from basic ! 

 

I wrote a basic program that converts a sprite to ml code.. so instead of the usual read data..draw to screen.. repeat... this just draws the needed pixels ... with transparent background

 

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