Turned off, Water Layer contains the height of the water column at each voxel. Turned on, Water Layer contains the location of the water surface To change between the modes, go to the Output tab, and turn on or off Output Water Height is Absolute. The Shallow Water Solver differentiates between absolute and relative Water Layer values.

The simulation result–the solver’s Water Layer–is also a heightfield. The solver has a Source Scale parameter that can be used to tweak the amount of sourcing, but the sink field will be used as is. With a sink, and FG Value set to 0.5, only 50% of the incoming water will be deleted on each frame. A BG Value of 0, on the other hand, means that no water will be sourced or removed. With FG Value set to 1, sinks have full strength. For example, in the HeightField Paint node you can find FG Value and BG Value. You can also create separate masks for sinks or areas where forces are applied. You can also use the HeighField Mask by Occlusion and HeightField Mask by Object nodes, or combinations of different methods.

Another way is to import a single image or an image sequence for an animated mask. You can, for example, draw a mask with a HeightField Paint node. To create a water source, you need a mask. You can make yourself familiar with fundamental concepts under Basics of heightfields. Heightfields play a central role in the Shallow Water Solver.

Water houdini