Just having great fun with this apprentice licence, ive been usng maya for too long and guess my mind needs a bit of a wash to understand how attr data flows in houdini…
Im talking in POPS world here:
As I understand, everitime I need an attr value to be called in an expresion i must be very careful to see if it can be called as a Local variable (by checking the nodes local variable)otherwise i must “create” one using an attribute node or use the “point” command (not sure if this is the way in POPS)
My problem is, I have created a VOP POP node which makes an effect, it works fine and I want to access the output values of an attr created inside that VOP POP in another node (in my case its the creep node) later in the network.
now if i Check the detail panel I can see my attr with the different values flowing for each particles,the way it appears is (lets call the attr “uvpos”):
uvpos uvpos uvpos
so when i try to load the values to the u and v of the creep node, im having a bit of a hell.
obviusly i just need the first 2 attr values and .
the attr was created as a vector inside my VOP POP node,the way I call the attr inside the vop node is by using an invisible parameter with the same name and by piping the result of a chain of operations to an “add attr” node also with the same name, so i get the attr values that I want.
Now
creep doesnt know anything about this “uvpos” attr ,so I create a new attr with EXACTLY the same name as the attr I want to use (in this case “uvpos”) as a vctor, but what i got is:
uvpos uvpos uvpos
worst of all, when i try to pipe the values Hudini wont recognize the variable definition as:
$UVPOS1 $UVPOS2 $UVPOS3
and if I use
$UVPOSX $UVPOSY $UVPOSZ
it does recognize but pipes to itself the values (obviusly) of uvpos uvpos uvpos and i need uvpos uvpos uvpos
the “point” command was not succesful either… not sure what do i need to use instead of “$PT”
so to summarize and apologize for the long text, how can i read those values in to the creep node?
this is very frustrating and i belive the way attr and local variables work is not helping with the learning proccess
as a quick challenge:
make some particles collide to a geo ad the “Add Hit position UV” attr , and split some particles out of them, then try to call this “hitposuv”in vop pop by using a parameter node or an “Import attribute” with the same name, no mater what signature i select it wont load the values
with other attr i works fine…just need to be careful with the signatures…
finally, im sure there is a way when i use an import attr node to change the “adata” to something that makes more sense! this is the reason why i use parameter nodes instead.
thanks guys!
love the program.
