Point wrangle - conditional setting of attribs

[adamvanner]

I have a python SOP otl im converting to VEX using the PointWrangle SOP - the OTL processes attribs that may or may not be present; I'd need to keep this behaviour. But.. I noticed that:

 

vector orient;

if(isbound("my_attrib"))

{

    import("my_attrib", orient, 0);

    orient = some_blah(orient);

    v@my_attrib = orient; // CREATES the attrib even if isbound() is false

}

will create @my_attrib, even if it doesnt exist. I tried this:

 

if(isbound("my_attrib"))

{

    import("my_attrib", orient, 0);

    orient = some_blah(orient);

    setpointattrib(geoself(), "my_attrib", @ptnum, orient); // Doesnt create, but doesnt work either

}

 

But, maybe a limitation of PointWrangle, this does nothing.

 

Any other ways of setting this attrib?

Thanks!

[MENOZ]

I'm not super expert in vex, but shouldn't you use addattribute instead of setpointattr ?

 

 http://www.sidefx.com/docs/houdini13.0/vex/functions/addattribute 

 

 

EDIT:

i'm not sure what you want to do, but if you want to check if you have an attribute you can use "haspointattrib" function.

 

in a pointWrangle, this works for me.

 

if(haspointattrib(0,"my_attribute"))

{

    addattribute("newAttrib",5);

};

 

 

 

I don't know how to create an attribute in an attributeWrangle.It doesn't seem to recognise  the addattribute function. I can Set an existing attribute but not create one, without using the @ syntax

Edited July 12, 2014 by MENOZ

[adamvanner]

ahh that looks like a much more appropriate function thank you!,.. shame it still doesnt seem to set the value (it does when I use @my_attrib)

 

Ive tried this and this:

addattribute("my_attrib", orient);

addattribute("my_attrib", orient, "type", "vector");

 

so to sum up:

 

This works (but always adds the attrib, even when I dont want it to)

v@my_attrib = orient;

 

This doesnt

addattribute("my_attrib", orient);

 

which seems odd?

[MENOZ]

I didn't tried this yet, but to set an attribute you should use a separate function like setpointattrib.

 

http://www.sidefx.com/docs/houdini13.0/vex/functions/setpointattrib

 

 

the reason why @ always is executed is in another thread:

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=151709#151709

 

hey Adam, I've just read your name, is it you from dneg?

[anim]

just to be clear not all VEX function work in all VEX contexts 

so pointwrangle has import(), addattribute() and no setattrib()

attribwrangle has setattrib() functions and no inport(), addattribute()

 

those 2 functions are similar but not equivalent, for your case though they both should do what you want

@ syntax always creates the attribute as it's mapped to export variable, unless you exclude attribute's name from exporting, in that case @ would only read 

 

so if you want to avoid @ syntax

in pointwrangle use:

vector attr = 0;


if ( import("my_attrib", attr, 0) ) 
{
    attr += {1,1,1};
    addattribute("my_attrib", attr); }

for attribwrangle:

vector attr = 0;


if ( haspointattrib(0, "my_attrib") ) 
{
    attr = point(0, "my_attrib", @ptnum) * {2,2,2} + {1,0,0} ;
    setpointattrib(0, "my_attrib", @ptnum, attr, "set"); 
}

 

[adamvanner]

 

in pointwrangle use:

vector attr = 0;


if ( import("my_attrib", attr, 0) ) 
{
    attr += {1,1,1};
    addattribute("my_attrib", attr); }

 

 

 

Thanks Thomas, yes I tried exactly this in PointWrangle but even in a very simple case - literally as you have but a different attrib name, assigning using @ works fine, but with addattribute does nothing.. its odd- I dont see what Im doing wrong - could run this in the VOPSOP instead, but this should work?

 

 

hey Adam, I've just read your name, is it you from dneg?

 

Hey Andrea! Ha yes I should have just waited until tomorrow to ask you about this in rounds, eh?!

[anim]

not sure what doesn't work for you do you have non-working example?

here is an example which modifies attribute only if exists (both point and attribwrangle) , if it doesn't it will not create one

 

created in H13

 

modify_attr_only_if_exists.hip

[adamvanner]

ahh great - yes so looks like it was the use of isbound() - I guess that is detecting attribs bound using @ notation rather than being present in the inputs.. all working perfectly with haspointattrib(), import() and addattribute() .. thanks a million!

Edited July 14, 2014 by adamvanner