Houdini - erosion

Houdini terrain master class 1

Houdini terrain master class 2

Houdini use with Unreal

UI

user interface layout can be selected and reset in :

Menu -> Build

Heightfield 

height field is create around the center with the radius as half of the size axis.

grid spacing : large spacing create less resolution.

heightfield paint

paint mask on the height field, need to enable show handle to show the brush

lmb to paint mask

mmb to erase

mouse mmb scroll to change brush size

masked part will show red

heightfield noise

create noise on the height field
input1 : heightfield
input2 heightfield mask








combine Methods : calculation methods btw heighfield and noise


amplitude : change the maxim height of the noise


element size : size of noise


noise type : Worley (cellular ) Manhattan worley is very useful to create chunky flat area on terrain.

geometry and transform & heightfield

geometry can be projected onto a heightfield:

transform node transform the geometry
heightfiel_project project the geometry onto the heightfield.
input1 : heightfield
input2 : geometry

heightfield distort by noise

use noise field to moves the existing values
a compare btw ditort by noise and heightfield noise

heightfield layercomposite two heightfield layers

input 1: hf1
input2 : hf2
input3: maskheightfield File

heightfield file

heightfield file import image to heightfield

heightfiel distort by layer

the distortion can be control by another layer of heightfield 

the distortion keep the shape of the basic terrain layer as well as bring in some feature by the add on layer.

input1 : hf to be distort (terrain)

input2 : addon hf (noise)

compare of before distortion and after

heightfield mask clearer

clear the red mask visually for better

heightfield erosion

visulization: create color scheme for terrain

Place to reset simulation and freeze a frame (where you decided is the final result and don't want to touch it anymore)
to start an erosion : left bottom corner

Global Erosion Rate : higher rate has higher erosion effect

MainTab

• Hydro : erosion cause by water

Bank Angle : smaller value create wider and flatter river bank, high value cut deep into terrain, a rule of thumb is use high value when creating the basic mass form.
spread iteration : higher number cause the river run longer

• Thermal erosion : rock becomes sand

cut angle : control where erosion start, low value allow more erosion, higher value create cap on the mountain

advanced Tab

• Hydro Erosion

removal rate : remove the debris by wind. set to minus can add more debris. It is useful to create muddy effect.

max debris Depth : allow thicker debris build over time.
Grid Bias : Control the direction of erosion

Erodability

initial factor : this increase the strength of erosion 

slope factor : low value enable flat area has erosion, higher value constrain the erosion in sharp slope area.

Riverbed

erosion rate factor : higher value cause deeper cur deep in the river. less value cause scattered isolate lake effect.

deposition rate : higher value cause earth hard to erode.

sediment capacity : how long can sediment go with the water. cause water go further in narrow area, also create mud in flat and wide area.

RiverBank
erosion rate factor : high number cause more erosion on river bank. wider river bank
Max Bank to Bed Water ratio : how much is consider as bank

thermal erosion
has the similar set as hydro erosion

Preciptation
this is where the rain wash down the debris. hydro erosion will need this to take shape.
amount : higher number more rain
density : higher number detail branches on the water path

raindrop setting
expand radius : channel and water area becomes larger in larger value

Debris flow
spread iterations : higher value make debris spread wider
quantization : higher value cause debris to be more chunky
water absorption : the higher value create a muddy and narrow water bank. lower value create wider and flater area.
max height : how high the debris can climb up to the mountain when it is washed down.
repose angle : the angle debris can stand until it falls down

layer
layer is options for multi-layer erosion, either delete or keep previous erosion effect.
remove layer and delete layer :
remove layer still keep the water / debris but they do not calculated in erosion, this is good for adding details on the second layer of erosion
delete layer : useful for when want to keep the form of previous erosion but create data set separately.
add layer to final height : bake the layer to the heightfield

heightfield remap
remap the height of a terrain, normally it will become more realistic.

heightfield blur can be use to blue the heightfield after erosion to create realistic result.


normal noise and chbyshew workey noise to noise but also hard line on top of the mountain, the size of the noise is the key to achieve good result.


heightfield resample
increase the resolution of heightfield
useful when finish the first layer of erosion and before go to the second layer.

heightfield



heightfield_slump


heightfield_flowfield
add the existing flow into the dataset.