The Volume Arrival Time SOP computes how long it takes to get to every voxel in the volume. This time is measured from a provided set of start points. The time taking to cross each voxel is a function of the incoming speed field.
You can take the gradient of the resulting field to get an estimate for the most efficient way to get to one of the seed points.
This node currently only works with standard Houdini volumes. It does not work with VDBs.
The volume to use for the speed field. 0 areas will inhibit travel from the source points, 1 areas will allow for fast travel.
See specifying volumes for more information.
Arrival Field Name
A new field of this name is created to store the resulting arrival time at every voxel. It is the same resolution as the speed field. When processing more than one volume, this parameter can contain a space separated list of names (optionally in double quotes), where the name of each new field will be its index modulo the number of names in this parameter.
The times are all scaled between the smallest and largest found time.
Any times greater than this at the end of the solve are just replaced by the maximum time that is not greater. This avoids unsolved areas from getting very large values that can lead to computation problems. Setting this greater than 1e10 and turning off the normalize times will result in the raw output of the solver.
How accurate the resulting arrival times have to be before the iteration is stopped.
Even if a solution within the tolerance is not found, the process will still be stopped if this number of passes has been done.