Accessing Attributes In Pops

[henderthing]

OK--

So if I add normals to my emission geometry w/point SOP, I can access them easily enough in my source (or any other) pop with $NX, etc.

However, I've created a vector point attribute called upv, using a VOP SOP, and it is mapped to $UPV.

In my source POP, I tell it to inherit all source attributes and create local variables. The attributes show up in the spreadsheet in any pop I select, and their values are valid, yet I get errors any time I try to use $UPV0, $UPV1, etc. So I try poppoint($PT,"upv",0). That works in any POP downstream of source, but it will *not* work in the source POP--where I'd really like to set initial velocity. Why is this?

The workaround for now is to create a group using rule $AGE==0, then use the velocity POP on that group. It works, but what is going on in the source POP? How can I access my own attributes as local variables within POPs?

Any insight is welcome.

Thanks

-m

[sho]

Hi,

Well I'm not sure why we can't use local variable in SourcePOP, but my understanding is, it's not created(cooked?) in SourcePOP its self.

So I always use birth group and feed initial velocity using VelocityPOP.

Also, you may need to use $UPV1, $UPV2, $UPV3 for three floats...

Cheers,

Sho

[henderthing]

Thank you!

Still getting used to this stuff. So many things in Houdini index starting at 0, so many others with 1... <sigh> Of course I kept testing with just x (0). Doh.

-m

Hi,

Well I'm not sure why we can't use local variable in SourcePOP, but my understanding is, it's not created(cooked?) in SourcePOP its self.

So I always use birth group and feed initial velocity using VelocityPOP.

Also, you may need to use $UPV1, $UPV2, $UPV3 for three floats...

Cheers,

Sho

22033[/snapback]

[deecue]

are you sure it was a vector and not maybe just a float of size 3?

as edward was pointing out in this thread, a float attribute will have variables $VAR1, $VAR2, $VAR3.. where as a vector attribute will have $VARX, $VARY, $VARZ.. if you are unsure as to what type and size your attribute is, you can click on any sop and select 'extended information'. This will list all your attributes (point, prim, detail, vertex, custom) and their size and type (as well as some other handy info as well)..

hth,

dave

[henderthing]

Yeah--it's all working fine now, but I was still a little confused as to when the attribute becomes 3 floats. In the VOPnet it's a vector, the input to the addAttrib node is a vector, the addAttrib node says "vector signature" at the top of the parameter panel, but at the sop level, the attribute is clearly 3 floats.

Now I see that this is the default behavior of the addAttrib node, and there is a checkbox called "Vector Qualifier" that can cause the attribute to be a vector at the SOP level.

Good times.

Thanks

-m

are you sure it was a vector and not maybe just a float of size 3?

as edward was pointing out in this thread, a float attribute will have variables $VAR1, $VAR2, $VAR3.. where as a vector attribute will have $VARX, $VARY, $VARZ.. if you are unsure as to what type and size your attribute is, you can click on any sop and select 'extended information'. This will list all your attributes (point, prim, detail, vertex, custom) and their size and type (as well as some other handy info as well)..

hth,

dave

22073[/snapback]