Node Tree Traversal
When the node tree executes or updates the Mesh Output node traces backward from input to output throughout the node tree to determine what nodes to calculate. If a node is not connected, whether directly or indirectly, to the Mesh Output it will not be calculated.
Duplicate nodes (nodes of the same type with the exact same settings) are not recommended as each node will be calculated. Think about this before adding new inputs especially Grid nodes! Utility nodes shouldn’t be a problem though.
Cached Node Results
Node calculations are saved and will only update if a node behind it is added or changed. So once the Noise or Hydraulic/Thermal erosion nodes run any other node you place after will not recalculate said nodes when any settings are changed on the new nodes. If you are getting weird results click the “Execute” button in the header. This will recalculate all nodes.
I Am Speed
Most nodes are incredibly fast and can make changes in near real-time (depending upon Density). The Erosion nodes can be the slowest as they are simulations and not just math operations. Noise nodes also can be slower depending on the Density.
Turning on debug mode from the Addon Preferences (Edit > User Preferences > Addons > NodeScapes) or header menu will show you how long each node takes to execute.
Every time you “preview” (CTRL + SHFT + Left Click) a node it will execute that node’s calculations. If you want to switch between 2 nodes where one or both are slow to see their outcomes connect them to a Mix node and switch between them using the fac. This way it won’t calculate those nodes.