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| Since | 21.0 |
This node uses rainfall and weathering to simulate the removal and transport of material, at a scale specified by the Erosion Feature Size. Larger scaled erosion can reshape terrain into broader landforms. Smaller scaled erosion can carve finer details. You can chain Numerous HeightField Erode nodes together to create erosion features at multiple scales.
Note
HeightField Erode will produce very similar features if the resolution of the input terrain is changed.
This node can simulate a range of frames altogether, or each frame iteratively. When you turn on Freeze, a range of frames are simulated from the start frame (Start Frame) to the frozen frame (Freeze at Frame). When you turn off Freeze, this node works iteratively with the playbar.
Tip
It’s recommended to freeze the eroded output once the desired amount of erosion has been reached. If you chain several unfrozen HeightField Erode nodes together, they may not cook sequentially, leading to unexpected results or increased cook times.
Most parameters in this node can vary spatially if a supplementary mask layer is provided (see Masking for a guide on masking HeightFields). The Erodability parameter can scale the effects of erosion, and its supplementary Erodability Mask can restrict erosion to masked areas.
Several output layers are generated, including eroded height, sediment, debris, flow and flowdir. You can use these layers for visualization with the 
HeightField Visualize node, or for texture synthesis inside of Copernicus networks. See Erosion for a more detailed guide on eroding terrains in Houdini.
How to ¶
-
Navigate to the Terrain FX shelf tab.
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Create the Terrain: Mountain preset, or the Terrain: Canyon preset.
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Go to the Start Frame, then click
in the playbar to play the simulation. -
Freeze the output by setting Freeze at Frame to a preferred frame.
-
Try appending another HeightField Erode node; change its Erosion Feature Size to a finer scale.
入力 ¶
Terrain to Erode
The HeightField to erode. You can bind named layers in the Layer Bindings tab. You can also create auxiliary output layers as newly named primitives. You can reset existing auxiliary layers to zero at the beginning of the simulation.
Masks
Optional input masks. To use a mask with a parameter, wire the mask into the second port, change the parameter’s associated mask setting to Mask On, and bind the mask by its primitive name.
パラメータ ¶
Reset Simulation
Clears the entire simulation cache. ⌃ Ctrl-click to also reset to the start frame.
Freeze
Freeze the output at the specified frame. When turned on, the entire frame range is simulated from the start frame to the frozen frame. When turned off, the node cooks iteratively with each frame.
Freeze at Frame
The frame to freeze the output at.
Solver ¶
Erosion Feature Size
The width of erosion features, in meters. Higher values will create wider channels, slopes, and deposits. Lower values will create sharper features. The smallest possible feature size is 3× the input terrain’s voxel size: features will be clamped to this size.
Note
This node will usually produce very similar features if the input terrain is resampled. Although, the features can differ if the feature size was clamped.
Spread Iterations
How many iterations of material transport to simulate in each frame. The number of iterations, together with the Erosion Feature Size, control the distance that eroded material can be transported within a single frame.
Random Seed
The seed used to randomize the erosion process.
Erodability
How prone the terrain is to hydro and thermal erosion. You can use the supplementary Erodability Mask to restrict erosion to masked areas.
Flow Force
The force of hydro erosion. With 0 you turn off hydro erosion.
Bank Angle
Controls the angle of channel walls. Higher values will create steeper channels that appear to cut deeper into the terrain, creating a jagged appearance.
Rainfall Coverage
The amount of rainfall to simulate each frame as a proportion of the terrain’s surface. This controls the intensity of hydro erosion in each frame.
Slope Influence
Controls how closely streams will follow the slope of the terrain. Lower values will result in straighter channels. Higher values will result in winding channels.
Erosion Rate
The rate at which a stream erodes and accumulates material from the terrain.
Deposition Rate
The rate at which a stream deposits its excess accumulated sediment.
Removal Rate
The rate at which a stream’s accumulated sediment decays. Higher values will reduce the amount of deposited sediment, allowing hydro erosion to cut deeper into the terrain, creating a rocky appearance.
Evaporation Rate
The rate at which a stream’s sediment capacity decays. Lower values will create more prominent channels that persist across longer distances with a rocky appearance. Higher values will create smaller local depressions with a soil-like or sandy appearance.
Weathering Force
The force of thermal erosion. With the 0 you can turn off thermal erosion.
Cut Angle
The angle that thermal erosion will cut until. A lower angle will make the cuts flatter, and allow for more thermal erosion to take place.
Repose Angle
The angle at which the thermal erosion debris will remain in place without sliding.
Layer Bindings ¶
Height Layer
The name of the layer containing the height to erode.
Debris Layer
The name of the layer containing the amount of deposited debris from thermal erosion. If Reset is turned on, the layer’s values are reset to zero on the start frame.
Sediment Layer
The name of the layer containing the amount of deposited sediment from hydro erosion. If Reset is turned on, the layer’s values are reset to zero on the start frame.
Flow Layer
The name of the layer containing the flow of eroded material from hydro erosion. If Reset is turned on, the layer’s values are reset to zero on the start frame.
Flow Direction Layer
The name of the layer containing the average flow direction of eroded material from hydro erosion. If Reset is turned on, the layer’s values are reset to zero on the start frame.
Add Debris Layer to Final Height Layer
Adds the amount of accumulated debris to the output height layer.
Add Sediment Layer to Final Height Layer
Adds the amount of accumulated sediment to the output height layer.
Simulation ¶
Start Frame
The frame on the Houdini playbar where the simulation starts. If Freeze is turned, all frames are simulated from the beginning frame (Start Frame) to the frozen frame (Freeze at Frame).
Iterations
How many iterations of the simulation to run per frame. Higher values create stronger erosion effects, but also take longer to simulate, because the erosion process is executed once per iteration.
Cache Simulation
Cached Frames
How many frames behind the current frame to keep cached.
Checkpoint Rate
The rate at which the node continually caches a single frame.
For example, set this to 5 to cache frames 5, 10, 15,
and such. This allows random-scrubbing to be faster as it only
has to re-cook from the checkpoint frame.
Set to 0 to turn off checkpointing.
