# Calculation question dealing with spin

sal22 shared this question 1 year ago

I can get pt_start and pt_end to "rotate circularly" when the freq_1 and freq_2 are 1hz

but if I change freq_1 (1.5hz) or freq_2 to a different frequency pt_start and pt_end no longer rotate circularly. I know it has to do with the calculation not taking into account the new frequency and the phase shift. Any ideas how I should adjust the calculation to correct shift_1 and/or shift_2?

I included two animations that shows the correct spin and another animation that shows what happens when I change freq_1 to 1.5hz which causes the wrong spin.

I also included the ggb file. I'm just not sure how to adjust the calculation to maintain the "correct" spin if I change the frequencies of freq_1 and/or freq_2

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There is nothing wrong there. The applet works fine. If you use different frequencies you get lissajous curves. If it is wrong in your eyes you have to describe what you want to achieve.

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I added two animations one showing the spin I'm trying to keep marked Correct even if I change the frequency and one marked Wrong showing the spin when I change the frequency.

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I can see that you maybe want the movement of points in a circular pattern. You have to understand, that there is no 'spin' possible if there is a frequency difference. If you would study the curves you would discover that on some parts the curve will overlap and therefore the movement can not be circular. On the case f_1 = 1.5, f_2 = 1, and phase shift on both 0 you will even have full overlapping. The circle without frequency difference is a special case where the curve never overlaps an therefore it shows an steady 'circular movement'.

If you know this than you have to specify what in detail you want to achieve as i can not understand your aim. Maybe another forum user might understand you better.

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I think I see what I need to use. It's quaternions

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Quaternions as well as rotation matrices are used to rotate points/structures and not to 'manipulate functions'. None of your questions indicated that you want to rotate the resulting curve. Also mentioning frequencies was a grave mistake if that was your aim. As the frequencies paint the picture and do not manipulate the slope of that picture.