This class can be used to make the water of a WaterNode flow in user-defined directions and with user-defined speed.

Defining Flow:
Water flow is defined by three influences:

• BaseVelocity defines a uniform constant flow which is applied to the whole water surface.
• Water flow can also be defined by surface slope of the water surface. The slope is defined by the vertex normals of the water Volume. Water is usually running downhill. SurfaceSlopeSpeed defines the speed at which water flows down an inclined water surface.
• A FlowMap texture can be used to define a detailed, complex flow pattern. FlowMapSpeed scales the speed defined by the flow map.

Speed and Normal Strength Limits:
Flow speed from all three influences (base velocity, surface slope and flow map) is summed up and clamped to MaxSpeed. The intensity of normal maps should be reduced if the water moves faster. The normal map strength have full strength when the flow speed is zero. The normal map strength is reduced to MinStrength when the flow speed reaches its maximum (MaxSpeed).

Reference frame:
The BaseVelocity is relative to the local space of the WaterNode. The FlowMap is also relative to the WaterNode; it is aligned with the local axes of the node. It fills the local AABB, and the map is always projected top-down.

Rendering Flow:
Water flow is created by scrolling the normal maps of the water into the flow direction. If two points on the water surface have a different flow direction or flow speed, then this creates distortion. To hide the distortions, two layers of normal maps are alternated: One normal map layer fades in, is scrolled and before it gets too distorted it fades out. At the same time a second normal map layer is added but with a half cycle offset. CycleDuration defines the cycle period. The normal map cycling can cause pulsing artifacts. Noise can be used to hide this artifact, by giving each point on the water surface a different cycle offset. NoiseMapScale defines the scale of the applied noise texture in x and z direction. NoiseMapStrength defines how much noise is applied to each pixel (= how much a cycle can be offset). The noise map itself is always generated automatically.

Limitations: Currently, the WaterRenderer does not render WaterFlow when the WaterNode also uses WaterWaves.

Reference