Start loop from BPM question

[Mitch Mann]

Put a marker on the layer where the first beat hits. Then add that marker’s time to the time calculated in the last line of your expression. If its still not sync’ed, just nudge the marker back or forth.

[Toby Royce]

I’ve utilised the expression included in here (lifesaver) to animate the z position so that titles pump in & out from the camera in line with the BPM.

however I’m also having the same issue which I think Armand is referring to ..

I have a 4 bar loop of music at 130 BPM. Using the expression makes this loop very close to perfectly.

The fist beat of the first bar is at 00:00:00:00 in my sequence. But wen the animation of the title in z depth begins it is around mid way through a cycle of the sin wave, rather than beginning at the bottom or top of the wave. As a result it isn’t pulsing in sync with the other elements I have looping in the sequence..

Is there a way to control the beginning of the sin function so it begins at 00:00:00:00?

Cheers

Toby

bpm = 130;
mag = 500;
freq = bpm /60 /2;
z= mag * Math.sin( 1 * Math.PI*freq * time);
[1920/2,1080/2,z]

[Dan Ebberts]

You probably just need to adjust the phase angle. If you want it to start at its closest to the camera, you could do it like this:

bpm = 130;
phase = 270;
mag = 500
freq = bpm /60 /2;
z= mag * Math.sin( 1 * Math.PI*freq * time + degreesToRadians(phase));
[1920/2,1080/2,z]

Dan

[Toby Royce]

Thanks.. that’s opened my thinking more on this.

I did actually also find I could achieve it by using Math.cos instead of sin in the formula. but again this limits it to beginning at the position furthest from camera, so I like the precise control of the phase degree… Thanks

Toby