Terrain erosion sandbox in WebGl

controls :

• press keyboard c to do terrain editions with brush, editions include : add/subtract for water and hight map for now, you can also adjust size of brush
• press keyboard r to place permanent water source. (note : 1 . press r again to remove permanent water source, 2 . after it's placed you can see a red circle marking the location, 3 . the size and strength of permanent water is equal to the brush size and strength the moment permanent water source is placed)
• press button Start/Resume to the right top corner to start or resume the erosion sim
• press button Pause to pause the simulation
• press button Reset to reset simulation and start with a new randomly generated base terrain
• use WaterTrabsparancy slider to control alpha of water
• use EvaporationDegree slider to control anomunt of evaporation you want each simulation step
• use Kc slider to control Kc (erosion capacity constant)
• use Ks slider to control Ks (erosion dissolvating constant)
• use Kd slider to control Kc (erosion deposition constant)
• use the dropdown to check the debug views
• press right mouse button to rotate camera, press left mouse button to translate camera, use middle mouse to scale...

PLAY LIVE (Chrome Recommended)

Demo Video showing sandbox feature

Note : MacOS currently unsupported, Recommended GPU is GTX 1060 and above

update 12/8/2021 :

• Algorithm update/fix : added basic(semi-lagrangian) advection for velocity field generation, you can change magnitude of it under "Erosion Parameters" -> "VelocityAdvectionMag", this means that momentum is possible for water, we can have larger/better scale meandering/delta effects

update 10/1/2021 :

• Algorithm update/fix : now erosion detail will be more accurate as I've choosen to disregard small water body's contribution to sediment advection, it used to create noises in sediment result because when water volume goes below numerical limitation of the sim, velocity will be contributing the same to advection regardless of water size...

update 9/24/2021 :

• Added option to change simulation resolution

update 7/11/2021 :

• permanent water source is added, you can pressed r to place it, see controls for details
• added heatmeap for velocity magnitude in debug view, mapping color goes from blue to green then to red as the velocity size increases
• added MacCormack advection scheme for sediment advection, resulting in less numerical diffusion (referencing : ShaderX7 Advanced Rendering Techniques - starting page 207), you can find and toggle it on/off under erosionParameters in gui

some screenshots

• flow map and results after adding velocity advection, this will make sure water have momentum transfered from previous frame, making it more persistent and easier to form ravine/valley
  

• velocity advection also enables better delta/flood plain :

• permanent water in a river vally

• river vally dries up after some erosion

• alluvial fan (or at least a similar one) formed at the mountain exit

sediments advection in action

see detail.md for implementation details

Future Plans:

• Image(height map) I/O
• muti-layered(rock/sand/etc) erosion
• PBR
• adaptive simulation utilizing quadtree(or just tiles) for sim optimization
• Depth upsampling/downsampling for volumetric rendering optimization
• Better GUI & Visulization
• Terrain features like instaced tree placements
• other postprocessing effects (ray marched cloud for example, since ray marched Mie scattering is done, cloud should be fairly simple to work based on it)
• Biomes
• Eventual goal : Erosion based games, "FROM DUST" would be a good example

limitations are there however for grid based method

• mass conservation of sediment is not guranteed

Reference

• Fast Hydraulic Erosion Simulation and Visualization on GPU
• Interactive Terrain Modeling Using Hydraulic Erosion
• Volumetric Lights for Unity 5
• ShaderX7 Advanced Rendering Techniques : starting page 207