karl@sugar.uu.net (Karl Lehenbauer) (10/01/88)
I'm having some problems with a little technology demonstrator I'm cooking up. It is a lunar lander that vertically and horizontally scrolls a 320X200 screen over a 640X400 IFF ILBM using ScrollVPort. The problem is that when the screen is scrolling, the sprites glitch, show as vertical crud for the whole height of the display and such. I was wondering if anybody knows offhand what I should be doing that I'm not. It's possibly just a dumb bug inside the program, though, 'cuz it's kind of hacked, but it's so strongly correlated with the scrolling, I thought there might be something I missed. -- -- "Insert the disk at your own risk." -- Firesign Theater -- uunet!sugar!karl, Unix BBS (713) 438-5018
koster@cory.Berkeley.EDU (Anonymous user) (10/02/88)
In article <2716@sugar.uu.net> karl@sugar.uu.net (Karl Lehenbauer) writes: >I'm having some problems with a little technology demonstrator I'm cooking >up. It is a lunar lander that vertically and horizontally scrolls a >320X200 screen over a 640X400 IFF ILBM using ScrollVPort. The problem is >that when the screen is scrolling, the sprites glitch, show as vertical >crud for the whole height of the display and such. I think for scrolling the data fetch for each scan line must be one word earlier, which is where sprites 5,6 and 7 have their DMA channels. This is discussed in the hardware manual. The solution may be to only use sprites 0-4, or knock off one word at the beginning of each line, making it a 304 x 200 screen, or perhaps just shifting everything to the right by one word, and moving the H.POSITION knob on your monitor. The symptoms you describe (tall vertical lines, garbage sprites that come in and out) are exactly the ones I found when someone had his preferences display position way to the left, and was running a program that used sprite 5. That was REALLY fun to debug! I just assumed it was my fault, and just couldn't find the bug. David Ashley koster@cory.berkeley.edu
karl@sugar.uu.net (Karl Lehenbauer) (10/02/88)
[I curse the day I first started using an overscan Workbench] In article <6084@pasteur.Berkeley.EDU>, koster@cory.Berkeley.EDU (Anonymous user) writes: > The symptoms you describe (tall vertical lines, garbage sprites that come > in and out) are exactly the ones I found when someone had his preferences > display position way to the left, and was running a program that used > sprite 5. That was REALLY fun to debug! I just assumed it was my fault, and > just couldn't find the bug. Bingo. I shifted the screen to the right with Preferences and the problem went away. Whew, thanks to sub-24-hour news turnaround, I didn't burn too much time on this honker. -- -- "If it's soft and hard to find, it's wimpy!" -- Wimpy's Software -- uunet!sugar!karl, Unix BBS (713) 438-5018