Re: [stella] Angular movement

Subject: Re: [stella] Angular movement
From: "Eric Ball" <ericball@xxxxxxxxxxxx>
Date: Wed, 14 Jan 2004 21:29:08 -0500
> And that's only part way there - you still have to account for aspect
ratio (4:3) and you should normalise it into byte form (preferably 2 bytes
but YMMV).

No, not 4:3.  It's not the screen aspect ratio you have to adjust for, but
the pixel aspect ratio.  1.67:1 for NTSC, 2:1 for PAL.  (See the posts
earlier this month.)

Vx = speed/fps * cos ( angle ) / 1.67 or 2
Vy = speed/fps * sin ( angle )
(assuming X = X + Vx & Y = Y + Vy every frame)

for acceleration
Ax = accel/(fps*fps) * cos ( angle ) / 1.67 or 2
Ay = accel/(fps*fps) * sin ( angle )
(assuming Vx = Vx + Ax & Vy = Vy + Ay every frame)

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