How to find out the exact Frequency of F-Curve Modifiers

Question

I want to create harmonic looping animations using the built-in functions for F-Curve modifiers.

Example: move an object back and forth along the z axis in a sine motion.

In order to make a perfect loop, i need to figure out the exact frequency of the built-in sine function. The docs don't mention the frequency at all and the value to change the frequency "phase multiplier" is rather obscure to me.

Answer 1

It looks like the base modifier is set to f(t) = sin(t) . That is to say, f(0) = 0, f(pi/2) = 1, f(pi) = 0 and f(3*pi/2) = -1

So the frequency is 2 * pi (The curve repeats itself every 6,283185307... units).

If you want to tweak the frequency, say you want a cycle every 10 frames, multiply the phase by 2 * pi and divide by 10.

Answer 2

Phase Multiplier to generate 1Hz = 6.2831853069/FPS

Each frame is ~ 0.1591549431 Cycles (1/2pi)

So for a 24 FPS you get 0.1591549431*24=3.8197186344 Cycles per second So to convert this to 1Hz to get 1 Cycle per second your multiplier would be --> 1Hz = Multiplier * 3.8197186344 ---> Multiplier = 0.2617993878

Here is a generic formula for any specific FPS you are working in your project

1/(0.1591549431*FPS) would give you 1Hz for your project FPS.

To simplify --> (6.2831853069 * 1/FPS) = 1Hz **

If you are trying to sync this to music, convert your BPM to Hz then multiply the value that you found from (6.2831853069 * 1/FPS) to your note values**.

For example a quarter note for a 141 BPM song equals 2.35Hz, if I'm working in blender in 24FPS then my multiplier to sync to a quarter note in music would be (0.2617993878 * 2.35) = 0.6152285613 then use the phase offset to sync the wave to the downbeat of your music.

I have tested this and confirmed the music stays in sync with these values.

If you are using Ableton you can use this time calculator plugin to convert BPM to Hz https://ableton.expert/product/565427 or use any delay calculator that can convert BPM to Hz

Hope this helps