Re: [stella] Angular movement

 Subject: Re: [stella] Angular movement From: Glenn Saunders Date: Thu, 15 Jan 2004 00:24:27 -0800
Okay, I took the first set of formulas and made a webpage to see how the tables would look.

The number right after the .byte is supposed to represent a byte between 0-255. You can adjust the speed until all numbers fall within that range.

But to me it doesn't look like this would work because it's not symmetrical. No numbers repeat.

You'd at least expect 0 and 180 degree values on the Vy and 90 and 270 to be opposite on Vx.

What am I doing wrong?

http://www.homebrewgames.net/thedig/tools/animation.cfm

At 06:29 PM 1/14/2004, you wrote:
```> 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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