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Forum Index : Microcontroller and PC projects : CMM2 sprite screen flickering
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| freemesy Newbie  Joined: 26/07/2021 Location: HungaryPosts: 2 |
Hi to all forum members! I've got problem with programming CMM2 (gen 1.). The main goal is to move a sprite beyond the background. Or at least move a sprite beyond another sprite. When the move accurs (with next-move or show commands) the screen is flickering. The sprites always redraw and that cause a very ugly flickering effect. Do you have any idea how to achive the goal, not to flicker? In fact when I use the 12-bit mode the flickering is more worse then in 8-bit or 16-bit mode. Some time ago I tried to write a scroll rutine in 12-bit mode but it has got the same problem. When blit occurs the screen was alwas flickering (no sprite in that). I tried the getscanline function to make the blit or sprite move occuring when the scanline is out of the way, but no success, same result. Here's my code: option default none option explicit const vstart=150 dim integer i,j,cpos=4,pl=0 mode 1,12 colour RGB(White),RGB(Black) cls page write 1 box 180,120,440,440,1,RGB(Blue),RGB(Blue) for i=1 to 7 for j=1 to 7 circle j*60+160,i*60+100,25,1,1,RGB(Black),RGB(Black) next j next i sprite read #1,180,120,441,441,1 circle 400,80,25,1,1,RGB(yellow),RGB(yellow) circle 400,80,27,4,1,RGB(180,180,0) sprite read #2,373,53,55,55,1 cls page write 0 cls sprite show safe #2,cpos*60+180,vstart,0 sprite show safe #1,170,120,0 waitforkey: if keydown(0)=0 then goto waitforkey if keydown(1)=27 then end if keydown(1)=32 then goto drop if keydown(1)=130 and cpos>0 then cpos = cpos - 1 endif if keydown(1)=131 and cpos<6 then cpos = cpos + 1 endif sprite next #2,cpos*60+180,vstart sprite move pause 150 goto waitforkey drop: ......... Thanks for your help, I hope somebody has got a godd idea. Zoltan |
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vegipete Guru  Joined: 29/01/2013 Location: CanadaPosts: 1082 |
I think you are just trying to draw too much. Nothing I've tried so far using sprites works cleanly - lots of tearing. The following uses BLIT and is better, but is still not ideal. It might be better to draw all the changing parts on page 2, then do a "PAGE COPY 2,0,B" to transfer it into view. Picking a lower resolution mode would help too. option default none option explicit const vstart=100 const xoffset=193 dim integer i,j,cpos=4,pl=0 mode 1,12 colour RGB(White),RGB(Black) page write 1 ' create game board on page 1 - front (static) image cls box 180,120,440,440,1,RGB(Blue),RGB(Blue) for i=1 to 7 for j=1 to 7 circle j*60+160,i*60+100,25,1,1,RGB(Black),RGB(Black) next j next i page write 2 ' create disc image on page 2 cls circle 27,27,25,1,1,RGB(yellow),RGB(yellow) circle 27,27,27,4,1,RGB(180,180,0) page write 0 ' draw disc on page 0 - background behind game board cls blit 0,0,cpos*60+xoffset,vstart,55,55,2 ' copy disc image at starting point do if keydown(0)= 0 then continue do if keydown(1)= 27 then end if keydown(1)= 32 then exit do if keydown(1)=130 and cpos>0 then cpos = cpos - 1 endif if keydown(1)=131 and cpos<6 then cpos = cpos + 1 endif cls ' erase everything blit 0,0,cpos*60+xoffset,vstart,55,55,2 ' draw disc in new position pause 150 loop for i = vstart to 494 step 5 ' drop disc down screen do : loop until getscanline > 499 ' trial and error - not ideal box 190,100,420,460,0,RGB(Black),RGB(Black) ' erase previous - smaller area would be better blit 0,0,cpos*60+xoffset,i,55,55,2 ' draw disc in new location pause 2 ' brief pause so video catches up next i do : loop until inkey$ <> "" Visit Vegipete's *Mite Library for cool programs. |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 8575 |
One big change would be to only redraw the sprite if it has moved. |
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| freemesy Newbie Joined: 26/07/2021 Location: HungaryPosts: 2 |
Thanks for your replies.  Vegipete's advice and code was perfect. I learn from that so much. It works like a charm. Thank you for your effort to explain things for an "almost beginner".  |
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| capsikin Guru Joined: 30/06/2020 Location: AustraliaPosts: 341 |
If I remember correctly my tile demo game here was able to move sprites around without flickering. It does it by calling the sprite move command right after a frame-blanking interrupt. I do remember it was harder to get rid of the flicker at higher resolutions - at 640x400 I only updated the screen every second frame, whereas I might have been able to update every frame at a lower resolution. 12-bit modes (and higher resolution modes) use more memory bandwidth to read the screen memory while displaying it to the VGA port, that's probably why they flicker more. |
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