Houdini_Procedural_City

This is practice project to generate a city in houdini procedurally using Python. Some of the important aspects ,where python is used, are loading building assets as well as setting attributes. There are two types of areas available in the map, one is the commercial which will have commercial buildings and other is house, which will have residential buildings.

NOTE: At many places, VEX or node based approach will be a better and faster approach but the intention of the project was to learn to implement things in houdini using python.

Important Code Snippets

1) Buidling Asset Loading

import os

#fpath gets the path to the folder containing building assets
buildings_path=hou.node(".").parm("fpath").eval()
buildings_name=os.listdir(buildings_path)

switch_houses=hou.node(".").createNode("switch","switch_houses")
switch_com=hou.node(".").createNode("switch","switch_commercial")
merge=hou.node(".").createNode("merge")
counter=0

#Variables to store the number of house 
#and commercial building assets present
housesCount=0
comCount=0

#The naming convention followed is
# commercial_{x} where x becomes the commercial building id
# house-{x} where x becomes the house id

for bname in buildings_name:
    if bname.endswith(".fbx"):
        #variables
        path=buildings_path+bname
        id=bname.split("_")[1].split(".")[0]
        type=bname.split("_")[0]
        
        #There will be four nodes for each building before merge and switch nodes
        #Nodes: file, bound, transform and attribute create
        #set the file node
        file_node=hou.node(".").createNode("file")
        file_node.parm("file").set(path)
        
        #set the transform node
        transform=hou.node(".").createNode("xform")
        transform.parm("scale").setExpression("ch('../u_scale')")
        transform.setFirstInput(file_node)
        
        #set the attribute_create
        attr=hou.node(".").createNode("attribcreate")
        attr.parm("numattr").set(2)
        
        attr.parm("name1").set("buidling_id")
        attr.parm("type1").set(1)
        attr.parm("value1v1").set(id)
        
        attr.parm("name2").set("buidling_type")
        attr.parm("type2").set(3)
        attr.parm("string2").set(type)
        attr.setFirstInput(transform)
        
        merge.setInput(counter,attr)
        counter+=1
        
        if type=="commercial":
           switch_com.setInput(comCount,attr)
           comCount+=1
           
        elif type=="house":
            switch_houses.setInput(housesCount,attr)
            housesCount+=1
            
        else:
            pass
hou.node("../CONTROL").parm("houseNum").set(housesCount)
hou.node("../CONTROL").parm("commercialNum").set(comCount)

2) Random asset assignment

import random

node = hou.pwd()
geo = node.geometry()

# Add code to modify contents of geo.
# Use drop down menu to select examples.
points=geo.points()
if len(points):
    houseNum=hou.node("../../CONTROL").parm("houseNum").eval() #Get the total number of house assets
    comNum=hou.node("../../CONTROL").parm("commercialNum").eval() #Get the total number of commercial building assets
    geo.addAttrib(hou.attribType.Point,"id",-1)
    
    #Set the end parameter for the randint function based on the type of point in map
    end=0
    type=points[0].attribValue("block_type")
    if type=="commercial" :
        end=comNum
    elif type=="house" :
        end=houseNum
    else :
        pass

for point in points:
    point.setAttribValue("id",random.randint(1,end))

Preview