Chunking up sine waves (one quarter at a time)

[sillybomb]

Hi I hope this actually makes sense. The picture might actually make this more confusing.

I am messing around with Sine waves trying to isolate various quarters of the wave phases.

I am trying to achieve a sine wave that reaches its peak then zeroes for another 3 phases i.e. just 1 quarter of the sine wave. Then I want to try and isolate the other 3 quarters. (End goal is to draw on all these quarters individually when I’m animating.)

I have drawn the kind of sine wave I’m attempting to achieve first next to some of my other attempts (charted up in excel) .

If anyone can please help me to isolate quadrants of the sine wave I would have a very nice weekend. 

Picture:

[sillybomb]

I know the rules - I shouldn't be replying to my own post but have passed the deadline to edit.  

I just thought of clamp() and that it might help. Still looking for the right answer though

[Mylenium]

That would simply be achieved by combining different functions inside the same equation. 6th grade math. The steep drop would be a simple threshold function intersecting with the sine, just the phase lengths would be different. Not sure what more you would need to know here.

Mylenium

[Mathias Moehl · Accepted solution]

Looks like you want the green curve whenever (time%1)<0.5 and the value 0 otherwise.

so you could use the expression

(time % 1 < 0.5) ? Math.sin(Math.PI*(time%1)) : 0

or the equivalent

if(time %1 < 0.5) Math.sin(Math.PI*(time%1))

else 0

[sillybomb]

Thanks Mathias - that was a great help exactly what I was looking for. Thankyou.

Rick also provided what I was after in another form. Thanks to you too.

Mylenium was helpful too in his own way. Thankyou. Yours is the third best answer of the three.

[Rick Gerard · Accepted solution]

Borrowing from Dan Ebberts Motionscript.com and Mathias Moehl's suggestion I came up with this to animate the position of a circle.

veloc = 200; //horizontal velocity (pixels per second)
amp = 300; //sine wave amplitude (pixels)
freq = 2.4; //oscillations per second

x = time*veloc;
y = amp*Math.sin(freq*(time % 1 < 0.5) ? Math.sin(Math.PI*(time%1)) : 0) - thisComp.height/2;

[x,- y]

The project looks like this: