# Curve from Expression

Hi,

I’m a Grasshopper newbie, and I’m trying to create a curve from a sine wave that is diminished in both the amplitude and the time domain (both x and z dimensions) using the golden ration (1/phi or .618…). I’m not a math guy, and so far I’m only able to get the sine wave showing in Rhino (6).

My thinking is that if I can insert a ‘multiplier’ before the x and z inputs of the ‘construct point’ module, each multiplier with the 1/phi value, that it should work. But I don’t know how to do this. And I’m guessing there’s a better way anyway.

Thanks for any clues!

Phi_Curve.gh (8.0 KB)

Hi Joe,

there is a multiply block you can use for that:

Phi_Curve_wd.gh (8.8 KB)

Does that help?

-Willem

It’s good to know now how to add that type of function as a component.
I was wrong, however, in thinking that would do what I wanted it to do - thus proving I feel asleep too often in math class.

Here’s a hand-drawn approximation of the curve I’m trying to create perfectly:

Thanks Willem!

The derivation is left as an exercise for the reader:

diminished sine.gh (6.0 KB)

2 Likes

I hadn’t really looked at this for a few years and didn’t realize some of the parameters limited the range, so here’s an updated version.

diminished sine - wider range.gh (7.0 KB)

[off topic] @akilli

i just checked your website out…

weird but, i’m pretty sure i live on the next street over from you… the one that starts with F

1 Like

I thought I felt a disturbance in the Force. We have to get together some time.

1 Like

sin.gh (10.0 KB)

Thank you Ethan! It will take me some time to figure out exactly what you’ve done here, but I greatly appreciate the head-start you’ve provided.