Get List of All Prim Groups in Python

[LukeLetellier]

I'm often bringing objects into Houdini that have 20+ primitive groups, and I'd like to figure out a way to easily split them up to put separate materials on each group, then merging them back together. Its rather tedious to do by hand - creating node after node and manually inputting each group name - so a scripting solution sounds like it would be much more appropriate. 

 

The psuedo-code would go something like:

 

sn = GetSelectedNode()
groups = sn.GetPrimitiveGroups()
 
for x in groups:
    Create Blast node
    Connect Blast to sn
    BlastGroup = x
 
    CreateMaterialNode
    Connect Material to BlastGroup
    MaterialGroup = x

 

I know how to do this sort of thing in C4D with Python, but I'm not sure of where to start with this sort of thing in Houdini; I've looked through the help guide, but couldn't find exactly what I needed. Thoughts?

    

[djiki]

You could do that by script, but also Houdini have Material node which gives you ability to assign bunch of materials to single object where each material could be assigned to specific group. This way you do not need to blast out separate groups and merge them back. Simply, connect Material node at SOP level and use "+" button to add as many materials you need and select which group(s) material should be attached to.

[f1480187]

import hou

node = hou.selectedNodes()[0]
mat = node.createOutputNode('material')
mat.parm('num_materials').set(0)

groups = [g.name() for g in node.geometry().primGroups()]
for i, name in enumerate(groups, 1):
    # Add instance to the multiparm on material node.
    mat.parm('num_materials').insertMultiParmInstance(i-1)

    # Set instance's Group and Material parameters.
    group = mat.parm('group%d' %i)
    shop = mat.parm('shop_materialpath%d' %i)

    group.set(name)
    shop.set('/shop/' + name)

# Select material node.
mat.setCurrent(on=True, clear_all_selected=True)
mat.setDisplayFlag(True)
mat.setRenderFlag(True)

Open Windows / Python Source Editor (code already there), then select node and press Apply. You can do much more than that. Such as create materials.

automat.hipnc

[LukeLetellier]

Oh my gosh, thank you. Will be diving into that this week!

[acey195]

you can also do this using VEX, using:

 

//

string groups[] = detailintrinsic(0,"primitivegroups");

int i,numGroups;

numGroups = len(groups);

 

for(i=0;i<numGroups;i++)

{

// code to assign your materials per group index

}

 

//

 

unfortunately this does not let you add instances to the multi parm automatically