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marcosimonrbl

Oct. 14, 2021 05:36:43

Hi,

I noticed there's a usd_parentpath() function but no usd_childpath()/usd_childrenpaths() function. I'm guessing this has to do with the wrangle being multithreading safe, but how would I go about the following problem otherwise:

All children prims hold an attribute (like polygon count) and I want to sum those up and write the sum as an attribute on the parent primitive.

rafal

Oct. 14, 2021 12:38:53

I've added an RFE for the `usd_childrennames()` VEX function.

If you know the children names, you can form the child path by appending "/" and a child name to the parent's path.

Otherwise, as a workaround for this task, you can try the Python LOP.

EDIT: RFE number is 116741

marcosimonrbl

Oct. 19, 2021 05:23:14

Cool!
Yeah we worked around with python - In general I prefer vex though, thanks for the RFE

goldleaf

Oct. 22, 2021 01:22:32

Another alternative approach could use two wrangles. The first would run on each mesh prim, and put the count value in a unique attribute on an ancestor primitive. Then the second wrangle would iterate over those ancestor prims, and sum the values together.

First wrangle (here we're counting the meshes on the "grandparent" prim):

// Get Point Count
vector pts[] = usd_attrib(0, @primpath, "points");

// Get mesh prim's name, as well as parent prim's name, to
// place a unique attribute on the "grand-parent" prim.
string parent = usd_parentpath(0, @primpath);
string grandparent = usd_parentpath(0, parent);

// Add and set counter attribute on the grandparent prim
string attrib = "counter_"+usd_name(0,parent)+"_"+usd_name(0, @primpath);
usd_addattrib(0, grandparent, attrib, "int");
usd_setattrib(0, grandparent, attrib, len(pts));

Second wrangle:

string attribs[] = usd_attribnames(0, @primpath);
string prefix = "counter_";
int total = 0;

foreach(string attr; attribs)
{
    if (startswith(attr, prefix)==1)
    {
        total += usd_attrib(0, @primpath, attr);
    }
}
i@totalMeshCount= total;

Might be useful until getting child prims is possible!

tamte

Oct. 22, 2021 03:59:00

Would also be cool if ust_setattrib() supported modes like "add", "append", ... Like setattrib() functions do
Then the second wrangle could be avoided in cases like this