acceleration pixels

[chad3006]

I need to know how to accelerate a background from 0 to some maximum number, smoothly.  I've modified some existing LB code but it has a constant movement rate.


 nomainwin
 WindowWidth=410
 WindowHeight=340
 graphicbox #w.g, 0,0,400,300
 open "Window" for window_nf as #w

 loadbmp "landscape", "SPRITES\bg1.bmp"

 print #w.g, "background landscape";
 print #w, "trapclose [quit]"
 timer 100,[scroll]
 wait
[scroll]
 x=x+5:y=y+0
 print #w.g, "backgroundxy ";x;" ";y
 print #w.g, "drawsprites"
[loop]
 wait
[quit]
 close #w
 end


[Rod]

nomainwin
 WindowWidth=410
 WindowHeight=340
 graphicbox #w.g, 0,0,400,300
 open "Window" for window_nf as #w

 loadbmp "landscape", "c:\basic\sprites\bg1.bmp"

 #w.g "background landscape";
 #w "trapclose [quit]"
 #w.g "when characterInput [speed]"
 #w.g "setfocus"
 speed=.25
 timer 100,[scroll]
 wait

[scroll]
 x=x+speed:y=y+0
 #w.g "backgroundxy ";x;" ";y
 #w.g "drawsprites"
 wait

[speed]
k$=right$(Inkey$,1)
if k$=chr$(_VK_LEFT) then speed = speed -.25
if k$=chr$(_VK_RIGHT) then speed = speed +.25
if speed <-10 then speed =-10
if speed >10 then speed =10
wait

[quit]
 close #w
 end



[chad3006]

Thanks Rod. If I understand this correctly, it accelerates at 25% to a maximum of 10, is that right?

[Rod]

Yep, you can set limits and change the step change value. The change I post is linear, you can of course change the speed on a logarithmic basis. But doubling the change, while natural, is hard to accommodate in such few pixels as we show. No right or wrong answer, experiment and see what works for you.