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# Issue about Catia curve from equation

## Issue about Catia curve from equation

(OP)
Hello everyone,

I am using Catia curve from equation to build a curve. Here is the formula for x and y:

So n is a parameter I defined. When n is small, the curve is a circle. However, when n is large, like n=100, it is not a circle anymore. Instead the curve is very weird.

How can I make sure that the curve is still a circle even when n is large? Because mathematically it should be a circle no matter how large n is. Any help is appreciated.

### RE: Issue about Catia curve from equation

how exactly did you implement your equations?
with x and t as variables in a Law (real), and R and n as external parameters?...

regards,
LWolf

### RE: Issue about Catia curve from equation

(OP)
LWolf, you are right. That is how I implemented. I even tried the following cases:
z=0mm*t
I changed 40 to 100, the curve is not a circle anymore.

### RE: Issue about Catia curve from equation

(OP)
Yes, I saw that video before and I followed the instruction. The only thing I do not understand is why the curve is completely different when I want to have more revolutions.

### RE: Issue about Catia curve from equation

I get the circle... (as I should), no matter how many revolutions (N number).
can you post a picture when you vary z=N*t ?...

regards,
LWolf

### RE: Issue about Catia curve from equation

(OP)
LWolf, below is my definition:
x1=25mm*cos(2*PI*1rad*100*t)
y1=25mm*sin(2*PI*1rad*100*t)
z1=0mm*t

The curve I got is shown below.

### RE: Issue about Catia curve from equation

yeah, seen the first picture.
did you use fog to define the laws?
could you humor me and show me a case when you vary the z

regards,
LWolf

### RE: Issue about Catia curve from equation

(OP)
Below is the result with z=100mm*t
Do you think maybe there is some settings that I should make? The result is really weird.

### RE: Issue about Catia curve from equation

(OP)
Yes, I used fog to define x,y,z. Then used curve from equation

### RE: Issue about Catia curve from equation

use real parameters, not lengths...

regards,
LWolf

### RE: Issue about Catia curve from equation

(OP)
LWolf, what do you mean by 'not lengths'? Please see my x1 definition below. In my definition, the type of x1 and t is length and real, respectively.

### RE: Issue about Catia curve from equation

welcome to 3DExperience

Eric N.
indocti discant et ament meminisse periti

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