Another cool thing: fixed point math

[+Random Terrain]

I was moving a sprite left and right and tried to slow it down with a counter. Looked like crap. I also tried to speed it up by adding or subtracting 2. Looked like crap. I then tried fixed point math. Whether you slow it down or speed it up to something like 1.5, it just looks smoother. I even cranked it up to 3.5 and it still looked pretty good. After playing around with fixed point math, there's no way I'd use a counter or plain old regular numbers again for sprite movement.

[Heaven/TQA]

yes...it was a miracle for me prior somebody explained me the magic behind fp maths.... first 8.8 then 4.4 then even signed.... and the real magic is... there is no magic behind it... just use it...

[MausGames]

I used a counter for my "TZ" demo, and I think sprite movement is pretty smooth. I start the single variable used at 50 though, and increase velocity depending on how far the variable moves toward 0 or 100. I prefer this method for the sake of saving a precious variable.

[+Random Terrain]

I used a counter for my "TZ" demo, and I think sprite movement is pretty smooth. I start the single variable used at 50 though, and increase velocity depending on how far the variable moves toward 0 or 100. I prefer this method for the sake of saving a precious variable.

Do you have time to make a quick, small program where you can move a simple object around the screen using your technique? Since there would be no extra code for other things, it would be easier to understand and follow.

 

 

Thanks.

[+atari2600land]

I just use this method Maus taught me:

  w=w-1 
if a{6} && w=0 then w=2 : player0x=player0x-w : rem move left  
if a{7} && w=0 then w=2 : player0x=player0x+w : rem move right

Edited May 25, 2008 by atari2600land

[accousticguitar]

I was moving a sprite left and right and tried to slow it down with a counter. Looked like crap. I also tried to speed it up by adding or subtracting 2. Looked like crap. I then tried fixed point math. Whether you slow it down or speed it up to something like 1.5, it just looks smoother. I even cranked it up to 3.5 and it still looked pretty good. After playing around with fixed point math, there's no way I'd use a counter or plain old regular numbers again for sprite movement.

Do you have a code example of this? I've been looking for a good example of fixed point variables but I haven't found one yet.

[+batari]

I used a counter for my "TZ" demo, and I think sprite movement is pretty smooth. I start the single variable used at 50 though, and increase velocity depending on how far the variable moves toward 0 or 100. I prefer this method for the sake of saving a precious variable.

Do you have time to make a quick, small program where you can move a simple object around the screen using your technique? Since there would be no extra code for other things, it would be easier to understand and follow.

 

 

Thanks.

You can use fixed-point math for moving players without using an extra variable and without needing to do something like Maus is suggesting.

 

When you set up your variables, do this:

 

dim p0pos = player0x.a

 

Then you may add a 4.4 or an 8.8 to p0pos and it will move your player, and you don't need to waste a variable - in this example, a becomes the fractional portion of player0x.

[accousticguitar]

Something like this?

  set romsize 4k


playfield:
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
X..............................X
X..............................X
X..............................X
X..............................X
X..............................X
X..............................X
X..............................X
X..............................X
X..............................X
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
end
    
    player0x=50
    player0y=50


    dim p0pos=player0x.a
    dim p0posy=player0y.b

    
main


COLUP0=28
COLUBK=22



player0:
001111
001111
001111
001111
end



drawscreen


if joy0right then p0pos=p0pos+1.5
if joy0left then p0pos=p0pos-1.5
if joy0up then p0posy=p0posy-1.5
if joy0down then p0posy=p0posy+1.5

 
goto main

Edited October 16, 2009 by accousticguitar

[MausGames]

Thanks Batari, great to know. My math and organizational skills are lacking, tips like this always help a lot. I hope a2600l sees this, I've been bugging him to try new physics.

Edited October 16, 2009 by MausGames