| From: | Jason Faramus |
| Date: | 3 Jun 2001 at 11:06:11 |
| Subject: | Line scrolling |
Hello,
> The only other thing I can think of ATM is doing the scroll in software
> onto another bitmap and then displaying the main playfield and blits on
> top of that. But that would be pretty slow.
I've tried doing the above David and have found it to work OK for what I need
it for but have one small probelm which I hope that you, or someone else can help
me with.
Instead of using display scroll to create a perspective effect I have cut out
each individual line as a seperate shape. Each shape is placed on the screen, each one
lower than the one before to create the graphic image (original .iff). Next, I test the joystick and
move each shape down the display a little faster on the x-axis than the line above
giving us the illusion of motion (albeit ALOT slower than proper Display Scrolling :( )
This works fine, I increase the x-axis 0.0125 for line one 0.0125*2 for line two
0.0125*3 for line three and so on for all the lines on the display, 50 in
total which is moved 0.0125*50. The problem is this, when the joystick is held
left the lines/shapes scroll properly with perspective to the left, when I hold
right they do the same to the right but when the display crosses the middle
section i.e. there inital positions, dead center I get an ugly pause. This in
effect is just like in DPaint when you have a looping anim and it has got two
identical frames in a row thus causing a pause. I think that the same thing is
happening and the same line/shape position is being shown twice as when the
joystick is moved either left or right when the display is dead center all the
shapes just shift 1 pixel to the left or right all at the same speed, just as if
you were moving them all as one whole shape. I cannot figure out how to cure
it though. Can anybody solve this (probably really obvious) problem for me?
Thanks and sorry for the long email.
Best wishes,
Jason.
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