[Tutor] Fwd: circular movement in pygame

[Dave Angel]

On 04/28/2015 02:37 PM, diliup gabadamudalige wrote:
> I thank all those who responded to my question
>
> Here is the code that I had written.
>
> When updating is applied to a surface object the rotation works but when it
> is applied through a class to an object it goes wrong in about 3 rotations.
> As far as I can see the code is the same. What is wrong? If you can correct
> some code and show me would help.
>

By top-posting, you're messing up the readability of your response.  And 
by trying to use an attachment, you're messing up a large portion of the 
people reading this thread.

Post a simplified example, inline in your message, and *following* any 
quote you're using.

If your symptom is that the data diverges eventually from the intended 
trajectory, the problem is that you're accumulating errors.  Each point 
you do you're rounding the calculation by storing it in finite 
precision.  After enough roundoffs, the error becomes visible.

If you need to reliably move an object in a circle, you'll want to store 
the location in angular terms, center, radius, and angle.

Then each time around the loop, increment the angle by a non-rounded 
amount, and recalculate the x/y coordinates.


-- 
DaveA