From: George Foot <mert0407 AT sable DOT ox DOT ac DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Smooth moving
Date: 6 Feb 1998 07:30:10 GMT
Organization: Oxford University, England
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References: <34D746D4 DOT 84EF3964 AT mail DOT htk DOT fi>
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On Tue, 03 Feb 1998 18:33:25 +0200 in comp.os.msdos.djgpp Henri Ossi
<henri DOT ossi AT mail DOT htk DOT fi> wrote:

: But again, one thing, that has always annoyed me is,
: that when the ball moves around the screen
: (I'd like to move it with float-numbers and use sin and cos
: to get the dx, dy variables counted)

Try making the game resolution much higher than the screen
resolution.  For example, make one pixel on the screen correspond to a
lot (e.g. 1 << 16) of units in the game.  Then you can get the angle
and speed very accurate, without having to add and subtract floating
point numbers (which should be slow).

You hinted, though, that you don't like one artifact of this system --
that the movement is effectively rounded to the screen resolution
when drawing the graphics.  There is no simple way to remove this :(;
antialiasing is one partial solution.

If you want to restrict yourself to 45 degree angles then you need to
scale down the increase in X and Y when travelling diagonally.  The
scale factor is of course sqrt(2), which is around 1.4; if you could make
your normal speed 2.8, when travelling diagonally you would want to
increase/decrease the coordinates by about 2 each time.  This means
that using 3 and 2 works fairly well.  To clarify, to move left/right
or up/down you would decrement/increment the X or Y coordinate by 3;
when moving diagonally you would alter both coordinates by 2.

I find, though, that generally it's better to use the fixed-point
system I mentioned first, and live with the (slight) jumpiness.  When
more is happening in the game it's not really very noticeable,
especially if the scenery is moving; players only really notice how
their character is moving with respect to the other characters.

-- 
george DOT foot AT merton DOT oxford DOT ac DOT uk

Remember what happened to the dinosaur.