VEX: Point rotate around curve axis

[morn66]

Hi everyone,

With VEX, I try to rotate a point around the closest point of a curve.

It seems to work for the rotation but the axis is off! I have no idea how to fix that.

here is the file

Vex_pointRotateAroundCurveAxis.hiplc

[LucaScheller]

Hi Julien,

you need to first transform the point to its local coordinate space before applying the rotation. This is done via (@P-hit_P), then you apply the matrix and finally restore the transform to the world position by adding hit_P again.

vector @P;

// Get the nearest hit attributes
int hit_prim_id = -1;
vector hit_prim_uv;
xyzdist(1,@P,hit_prim_id,hit_prim_uv);
vector hit_P = primuv(1,"P",hit_prim_id,hit_prim_uv);
vector hit_N = normalize(primuv(1,"N",hit_prim_id,hit_prim_uv));

// Rotate around the nearest hit point
matrix m = ident();
float angle = radians(ch('amount'));
rotate(m, angle, hit_N);
@P = (@P-hit_P) * m + hit_P;

 

I've gone ahead and updated your file. I've also switched to the xyzdist() instead of nearpoint() function to always get a smoothly interpolated Position and Normal.

If you have further questions let me know

Cheers,

Luca

 

 

Vex_pointRotateAroundCurveAxisFixed.hiplc

[morn66]

Oh wow! That works perfectly! Thanks for all the explanations!