How do I subtract one block shape from another when controlling Houdini through Python (Boolean operation in Houdini)? Have a house, want a window.

Please; does anybody know how you subtract one shape from another under Python program control?

If you can create the node network that performs that result, then it should be trivial to recreate that in Python. As a handy tip, you can ask Houdini to show you the code to create that node like this in the Python Shell window:
print hou.node(“/obj/path/to/node”).asCode()

When I try that I get a

NoneType' object has no attribute ‘asCode’

error message. Any suggestions?

Replace “/obj/path/to/node” with the real path of your node.

I call up the Python shell window, it says “source editor” but remains blank.
Then I type in

'print hou.node(“/obj/box_object2/boolean1/to/node”).asCode()'

but it generates no response. What am I doing wrong?

Got it. Was typing path wrong.
Now let's see if I can figure out the code for the boolean operation.
Great help so far. Thanks.

OK Wow, I got a lot more than I bargained for.
About 100 or so lines of code, in almost repeating stanzas that start with a cryptic comment, then an if statement to check for existence of object
The the following follows:

hou.parm = hou.node.parm('different parameters')
hou.parm.set('different parameters')
hou.parm.setAutoscope(False)
hou.parm.lock(False)

The first set of parameters include things like:autojoin, keepsourcecode, consolidateto1, dojitter, seed, overlapA, overlapB, closedA, closedB, insideAgroup, insideBgroup, insidetest, creategroup and many more

The second set of parameters include: Boverlap, Aoverlap, Ain, Bout, groupswitcher, 0, 1 and the hugely encouraging AminusB

How much of this is indispensable. Is there a short set of instructions, such as hou.parm.set(AminusB), and a couple more lines to establish who A and B are, that would do the job? I'm a bit swamped here. Help would be good.

Could anyone please tell me in simple terms how to perform a boolean operation on 2 volumes in Houdini under Python control?

I certainly wouldn't go this route. Why do you want to build this in python? Procedural workflow in houdini gives you much better options. Have you tried fore each loop or feedback sop?

Writing code is what I do.

With the guy I'm helping on a CGI project,
we feel limited on how much cityscape we can
produce creating the objects directly in Houdini.
Whereas with some random numbers and a few
do loops and object oriented programming, the
virtual environment can be made to go on forever.

Come on somebody, there must be a simple
way to perform a Boolean operation on Houdini
objects under Python program control.

I must agree with Kuba, if you were doing it in the GUI would be much easier. Have you thought of turning the house models into Digital Assets that you could then place in the scene using python? That might make things a bit easier. Also you can use ForEach SOP nodes to repeat operations like you'd do in a python loop. It'll probably reduce your memory footprint for large scenes…

Cheers

Hi Rafaels
OK, that might be the easiest route, but in our case, each house is different.
For the windows, for instance, their height, width and spacing will differ from house to house. Also a random function will determine whether at each interval there is either a window, blank wall, or a full length door. Some colonial houses have all doors. The only constant is that you must have at least one door. So the asset, controlled by Python might not allow for such flexibility unless it had it's random function incorporated.