The most challenging part for me was simulating drawing on water. While there are multiple ways to achieve this, making the strokes look beautiful and naturally dissolve into the water so that users feel they are drawing on a water surface, rather than in the air, is particularly difficult. Additionally, other animations needed for storytelling depend on the drawing process, and these effects can be resource-intensive.

After extensive exploration, the final product features a small pond made of several layers. The first layer is a plane with simulated water materials, while the second layer handles water simulation using Unreal Engine’s water plugin to simulate forces on the water. The physical water material detects user input vectors through line tracing. The strokes are created using a Niagara ribbon particle system, with changes in color, size, shape, and opacity over time to achieve the dissolving effect.