Fiddly vopsop/vex problem

[Macha]

I have some geometry with many points.

Each point has an $ATTRIBUTE_SCALAR.

I want to create another vector $ATTRIBUTE_VECTOR that points to the nearest $ATTRIBUTE_SCALAR with the same value.

For example:

-Point 12 has $ATTRIBUTE_SCALAR = 1

In it's neighbourhood we have

Point 11 with $ATTRIBUTE_SCALAR = 0.5

Point 35 with $ATTRIBUTE_SCALAR = 1

Point 785 with $ATTRIBUTE_SCALAR = 0.3

Then we would draw a vector from point 12 to point 35, and store it in $ATTRIBUTE_VECTOR because they have equal $ATTRIBUTE_SCALAR value.

Now, I thought this would be easy peasy with a point cloud and while loop but it turns out we cant write attributes inside such a loop. I get the error below.

It's likely there are multiple possible values for each point's $ATTRIBUTE_VECTOR, but I am not concerned about that for now (although even better if somebody finds a solution for that too!). I just need one vector (any of them). So we don't need to worry about that.

How can I do this?

Edited April 21, 2011 by Macha

[Macha]

Attached is a simplified hip file illustrating the problem.

veccol.hip

[Macha]

The file below contains a version of my failed attempt.

veccol.hip

[tjeeds]

I think this works

veccol3.hip

[~nature~]

Hi, Macha, Here is the vex solution, I hate vops concerning point clouds.

#pragma label filename "Lover File"
#pragma label matchattrib "Lover Attribute"
#pragma label direction "Lover Direction"
#pragma label maxsearchlovers "Max Search Lovers"
#pragma label tolerance "Lover Tolerance"


sop
nearest_lover(string filename="",matchattrib="",direction="";int maxsearchlovers = 30;float tolerance = 0.2)
{
    int maxlovers = min(Npt,maxsearchlovers);
    int handle = pcopen(filename,"P",P,1e+9,maxlovers);
    vector dir = 0;
    if(pciterate(handle))
    {
        float me;
        pcimport(handle,matchattrib,me);
        while(pciterate(handle))
        {
            float lover;
            pcimport(handle,matchattrib,lover);
            if (abs(lover-me)<=tolerance)
            {
                vector loverpos;
                pcimport(handle,"P",loverpos);
                dir = loverpos - P;
                break;
            }
        }
        pcclose(handle);
    }
    addattribute(direction,dir);
}

As for multiple possible values, how about pcfiltering the position of the matched lovers(you need to specify how many similar lovers are tolerated) based on your actual need ?

veccol_nature.hip

nearest lover.otl

Edited April 21, 2011 by ~nature~

[Macha]

Thanks to Jesse for wrapping his brain around so many nodes, and thanks to Nature for making it so simple with a few lines of code.

Definitely the time for me to review my vex typing skills!