The Paintable Puddles, Streams, Lava & Wetness module for MicroSplat add support for paintable wetness, puddles, streams and lava flows. A dynamic spawning system is also included, which allows water or lava to be poured over your terrain, flowing downhill.
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Once installed, enabled any or all features and use the included painting tool to paint these effects into your terrain. Flow direction is handled automatically so that the liquids always go down hill.
Don't want to paint your flows onto the terrain? You can generate them in realtime. Place emitters which cause lava or streams to start flowing downhill as you watch.
Requires the MicroSplat framework to be installed.