# trajpar

#### gggggggggg

##### New member
in the Files section, there are 2 good parts to download that were created with var. sec. sweeps utilizing the trajpar parameter in the sketch. these models are the flower & the bottom of bottle. could somebody explain the relation containing the trajpar parameter. i understand what trajpar is, but i don't understand how this parameter, used in the relation, creates the geometry.

#### noppenbd

##### New member
In the flower part, the initial sweep has a sketch relation:

sd3=sin(trajpar*360*10)*10

In this case, the relation does not take a single static value as we are used to assuming, rather, the value changes throughout the sweep feature. Because trajpar is a variable which varies from 0 to 1 through the path of the sweep, this relation allows sd3 to take a sinusoidal trajectory with an amplitude of 10 as the feature sweeps around its path. The sine function in ProE requires degrees, hence the 360 inside the parentheses. In addition, the multiplication by 10 within the parentheses accelerates the trajectory so that 10 sine wave oscillations occur during the sweep. You can rewrite the relation as:

f(t)=10sin[360* (10t)]

Where t is trajpar, and f(t) is dimension sd3. It should be fairly easy to see that at t=0, .05, .1, .15, .2, ... f(t) will be equal to 0. Likewise, at t=.025, .125, ... f(t) will be equal to 10.

I hope this makes it more clear.