Parametric equations in VEX

[davidyannick]

I need to  model a teardrop, the parametric equation is :

How can I implememt this in VEX ?

 

thx for your help

 

 

[DonRomano]

Well i guess it's something like :

float a = chf("a");
float b = chf("b");
float t = chf("t");

float x = a * (1 - sin(t)) * cos(t);
float y = b * (sin(t) - 1);

But depending on what you feed into the equation you may need to change from float to vector or vector4.

https://www.sidefx.com/docs/houdini/vex/functions/cos.html

 

Cheers,

[davidyannick]

5 minutes ago, DonRomano said:

Well i guess it's something like :

float a = chf("a");
float b = chf("b");
float t = chf("t");

float x = a * (1 - sin(t)) * cos(t);
float y = b * (sin(t) - 1);

But depending on what you feed into the equation you may need to change from float to vector or vector4.

https://www.sidefx.com/docs/houdini/vex/functions/cos.html

 

Cheers,

thx I've found, I had forgotten the domain of definition 

vector pos=0;
int pt[]={};

float q=chf("q");

int i=0;

for(float t=-$PI;t<$PI;t+=$PI/100){

    float aa=pow(q,2)*pow(sin(t),2);
    float ab=pow((1-q+q*cos(t)),2);
    float ac=aa+ab;
    float ad=q*sin(t)/ac;
    
    pos.x=q*sin(t)-ad;
    float da=q*cos(t)+((1-q+q*cos(t))/ac);
    pos.y=da;
    
    pt[i]=addpoint(0,pos);
    i++;
}

 

[Aizatulin]

Hi,

(just as personal preference) if you want to avoid for loops for creating parametric functions, just define the function in vex and apply it on an existing line (1d) or grid (2d).

teardrop.hipnc

Edited January 22, 2020 by Aizatulin