This is a waterfall/river asset in Unreal Engine 5, that can take in arbitrary geometry as input and produce foam when blocked by scene actors, and flow obstruction (transparency) at steep slopes. Additionally, Niagara particles simulate splashes where objects intersect with it.
Breakdown:
First the geometry is flattened by its UV coordinates using a vertex offset in material, this way ensures the entire geometry will be visible to the scene capture component regardless of shape. Then we sample distance fields from the original world position and write that to a render target.
Animated 'flattening to UVs' for demonstration only
The initial shader does a basic simulation that writes to a render target. This simulation involves:
1. Shifting the density field in the direction of flow
2. Decaying the density as it "ages".
3. Adding density where there is a significant change in slope.
1. Shifting the density field in the direction of flow
2. Decaying the density as it "ages".
3. Adding density where there is a significant change in slope.
Animating slope sensitivity parameter
The actual render material takes in this render target and interpolates opacity and foam based on slope and how “fresh” the foam is.
Niagara particles emitted from the water geometry add splashes where they collide with actors in the scene. Their initial velocity is derived from the mesh bitangent and flow direction. They are only rendered when a collision occurs to minimize overdraw.
Splish, Splash!
Potential Optimization Opportunities:
1. The initial scene capture could be run just once to store world positions in a lower resolution render target (and eventually to a static texture) and using that render target for the following steps. With this approach no further scene capture is required unless the waterfall actor is moved.
2. Updating the render targets only when needed; when waterfall is visible, near player, and overlapping a moving object.
2. Updating the render targets only when needed; when waterfall is visible, near player, and overlapping a moving object.
