>Dear GWorld Experts,
>I'm working on an app which, at the moment, simply bounces a circle around
>the screen (similar to the GWorld Example on the CD) and my code is based on
>Bill's GWorld Tutor.
>
>Is there any way to eliminate the comet blur effect during animation?
>
>My/Bill's animate function is as follows:
>
>
>local fn animate
>dim as rect dirtyRect
>'~'1
>dirtyRect = gCarRect
>FN copyBits(gBackgroundWorld,gScratchWorld,@gCarRect,@gCarRect,0)
>
>offsetrect(gCarRect,gDeltaX,gDeltaY)
>if gCarRect.left < 2 then gDeltaX = 2
>if gCarRect.right > 638 gDeltaX = -2
>if gCarRect.top < 1 gDeltaY = 1
>if gCarRect.bottom > 479 gDeltaY = -1
>
>FN copyBits(gSpotsWorld,gScratchWorld,@gCarSrcRect,@gCarRect,_transparent)
>unionrect(@dirtyRect,@gCarRect,@dirtyRect)
>FN copyBits(gScratchWorld,gScrn,@dirtyRect,@dirtyRect,0)
>end fn
>
>
>BTW I'm using PG.
>
>TIA
>Bernie


I won't take the label of expert. But I hope I can help.

You are possibly the victim of the _transparent parameter. Is that _Blend?

There is a comet blur effect that can occur when using Copybits or
CopyDeepMask and the _Blend parameter,  where you don't erase the earlier
sprite, and draw over it. It fades sequentially, depending on how you
handle that. Gives the comet effect though. Just change the parameter to
_srcCopy.

There is also the problem when using say a very white sprite on a black
background, the phosphor fade of your monitor as the pixels are lit. They
take small time to go "black" again.

All I can think, if this is ever a problem, is to change the color of your
sprite, or background, or reduce the speed of the animation.

Robert Covington