Hey.

Newbie alert !

I'm trying to understand how Houdini processes it's nodes on each frame. Coming from a Nuke background, where every node is evaluated on each frame, does Houdini work in a similar way ?

For instance, we have a Polyreduce node connected and I'm wondering if this is evaluated every frame or only when an option is changed and it needs to re-compute ?

Also, if so, what is the best procedure to combine all nodes (like maya's delete history) ?

Thanks

Eugene

If you middle-click on a node, it will tell you if it is time dependent. If a node has animation, it becomes time-dependent, along with all those downstream from the node, and will be evaluated each frame. Otherwise, Houdini will be smart enough to evaluate it once and keep it in memory. This isn't always perfect, for example, an imported alembic file will sometimes be seen as time-dependent, even if it's a static mesh. You can set a time shift node to a static frame to fix this issue.

You can use the red lock flag on a node (crtl-click) to force Houdini to evaluate the geometry and keep it in memory, it will also save the geometry with the scene file.

Tanto
You can use the red lock flag on a node (crtl-click) to force Houdini to evaluate the geometry and keep it in memory, it will also save the geometry with the scene file.

The other default way to do this is write a .bgeo.sc file to disk (using a file cache node) and read it back in.
Which of those two methods (locking and thus keeping it in the hip or caching to disk) is better depends on the situation and your general workflow and setup. I personally try to avoid blowing hip file sizes up, but there are moments where this is better.

What you generally don't do is throw away the network. It often happens that the geometry object where all the creation happens is not the one you use further in your project (you often create an empty one that just loads a cache or a reference to a cache), but in one way or another it stays. That's a big difference to all the destructive softwares out there where at certain intervals you merge down your modeling steps.