node evaluation

[964racer]

Hello,  What are the conditions in which Houdini nodes evaluate ?  I recently used a point wrangle node which I used to create

geometry on the fly using VEX functions such as addPoint(), addVertex(), addPrim()  etc. etc. Thankfully the code is evaluated once

in this node for those functions and the size of the node in number of points and primitives stays the same when I press "play".   But, if my node is doing

something dependent on time, I would expect the node to be re-evaluated if there is any upstream change to the graph (in a node "above"). How does

Houdini know the difference between these two cases ?  If the node is re-evaluated and there are any geometric creation functions in the body of the VEX

code, are they re-evaluated at every step ? 

Thanks

[symek]

SOPs are timeless by design. Your node evaluates whenever upstream geometry changes, so possibly at every frame it will repeat its work from scratch. Albeit this may seem wasteful, it's actually the reason SOPs are so flexible. Most nodes track upstream changes and evaluate only when something has changed. You can verify it by setting TimeShiftSOP (placed above your node) to a constant frame and check cook statistics for a given node. 

[koen]

Houdini is pretty smart about figuring out if a node is time dependent or not. The simplest way to check, is to middle click on a node and look at the bottom line, it will say "Time dependent cook: no" or Yes if it believes the node needs to be recooked with a time change.

 

Cheers,

koen

 

[Guest tar]

also Network Editor Display Options / Network View / Dependency -> Show Time Dependencies