 # How would one get xyzdist of surface based on range of vector directions

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I hope to get the nearest position on a surface or line that is somewhere along the inverse normal, searching in a range of angles (a cone if you will).

If this can be done in vex that'd be ideal (I've messed around sop loops and group stuff but that as expected gets very slow).

Too aid with the question there is an expertly drawn diagram. ##### Share on other sites

Hi,

You can fire rays for each given point within a cone in the opposite direction of the point normal:

Here is the VEX code:

```int numrays = chi("numrays");
float maxangle = radians ( ch("maxangle") );
float maxdist = ch("maxdist");
int visualize = chi("visualize");

vector phit = 0;
vector uvhit = 0;
float nearestdist = 1e32;
vector nearestp = @P;

for ( int i = 0; i < numrays; ++i )
{
vector2 u = rand ( i + 4523.4376 + @ptnum + ( @ptnum + 1 ) * 54.21 );
vector dir = sample_direction_cone ( -@N, maxangle, u );

if ( visualize )
{
int pt = addpoint ( 0, @P );
setpointattrib ( 0, "N", pt, dir );
}

int pr = intersect ( 1, @P, dir * maxdist, phit, uvhit );
if ( pr != -1 )
{
float dsq = distance2 ( phit, @P );
if ( dsq < nearestdist )
{
nearestdist = dsq;
nearestp = phit;
}
}

if ( visualize )
{
int pt = addpoint ( 0, phit );
setpointattrib ( 0, "P", pt, phit );
}
}

@P = nearestp;```

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