Houdini: Python
Workflow tip:
If you find yourself editing a lot of python code, you might like the joy of an external editor. Place your python code in $HOME/houdiniXX.X/scripts/python, for example as "test.py", then inside Houdini, drop a python node and do as follows:
import test
reload(test)
from test import *
Another cool way is to use the exec() function. Whan doing this, you do not need to worry about importing any stuff in your external file. I like the following:
(For example, in a python SOP, to read myfile.py in my home dir)
import os
home=os.path.expanduser('~')
pyfile=os.path.join(home,'myfile.py')
execfile(pyfile)
You can add frame=hou.frame() so the SOP will become time-dependent. Now stepping through frames re-evaluates your node. You can then edit the source file using your favorite editor.
Misc
Where on disk is my scene file?
hou.hipFile.path()
(hou.hipFile has a lot of options)
Get parameter
print hou.ch('parm')
Delete primitives
deleteList=[]
for i in boundingGrp.prims():
deleteList.append(i)
geo.deletePrims(deleteList)
Access local variables:
xBoundSize=lvar('SIZEX')
bang out point positions:
import json
node = hou.pwd()
geo = node.geometry()
pdata = []
for p in geo.points():
pos = list(p.position())
#print pos
pdata.append(pos)
with open('/tmp/points.json','w') as f:
json.dump(pdata, f, indent=4)
Point <> Vert mapping
sometimes you need the vertices that belong to a point. You can query the point belonging to a vert, but not the verts belonging to a point. For connectivity checks, you might find yourself needing that, so:
# store every vertex with it's point
def gen_v_p_dict():
dict = {}
for prim in geo.prims():
for vert in prim.vertices():
dict[vert] = vert.point()
return dict
# more useful to me, store all points with
# a list of vertices.
def gen_p_dict():
dict = {}
for prim in geo.prims():
for vert in prim.vertices():
pt = vert.point()
if pt in dict:
dict[pt].append(vert)
else:
dict[pt] = [vert]
return dict
Group related:
Create group:
myGrp=geo.createPrimGroup('name')
Add Point to group:
point=geo.createPoint()
myGrp=geo.createPointGroup('name')
myGrp.add(point)
Iterate group:
groups = geo.primGroups()
for group in groups:
print group.name()
Delete group, leaving contents intact:
group.destroy()
Attributes
Before setting an attribute, it must exist. Create it with:
geo.addAttrib(hou.attribType.Prim, 'myattrib', 0.0)
(In this case a primitive attribute)
Set attribute value
points[index].setAttribValue("Cd",(1.0,1.0,1.0))
Get attribute:
redVal=point.attribValue("Cd")[0]