Hey here is a python function that returns all unused materials of a scene. After a while Houdini scenes tend to have more and more materials that are not needed. This function helps to find all stuff that has no dependency in the scene. I’ve added a searchContext List that defines all the types of materials we were working with. So if you are working with other renderes (like vray or renderman), it is needed to add this type of materials to the list. If you don’t know your type of material, you can use the function in the third line. Simply put this into the python source editor, select your material and hit apply. The console should give you informations over the type.
import hou #debug Line if you want to add new searchContexts #print hou.selectedItems().type() #findUnUsedMaterails function #returns a tupple of materialpathes def findUnUsedMaterials(): #define an empty list that will returned in the end outList =  #set the search Contexts searchContext = [["mat", "principledshader::2.0"],\ ["mat", "redshift_vopnet"],\ ["mat", "redshift::Material"], \ ["mat", "materialbuilder"],\ ["mat", "arnold_materialbuilder"],\ ["shop", "RS_Material"],\ ["shop", "vopsurface"],\ ["shop", "redshift_vopnet"],\ ["shop", "arnold_vopnet"]] #loop over the searchContext variable for inContext in searchContext: #define the node Context Type, mat or shop if inContext == "mat": node_type = hou.nodeType(hou.vopNodeTypeCategory(), inContext) if inContext == "shop": node_type = hou.nodeType(hou.shopNodeTypeCategory(), inContext) #get all Instances of the Mat type Mats = node_type.instances() for Mat in Mats: #set a checker variable for adding materials to the outList checker = 0 #get all dependencies of the current material instance allDepents = Mat.dependents() #check if there are dependencies if allDepents: #loop over all dependencies of the material instance for currDepents in allDepents: #if there is an dependency set the checker to 1 if (currDepents.type().name() != inContext): checker = 1 #if the checker is still == 0, meaning that there is no dependency append the material path to the outList if(checker == 0): outList.append(str(Mat.path())) else: #if there is no dependency append the material paht the outList outList.append(str(Mat.path())) #return the list of unused materaials return outList print findUnUsedMaterials()
PS: If you are a tough guy, loop over the returned list and delete the nodes 😀
unusedMats = findUnUsedMaterials() for unusedMat in unusedMats: hou.node(unusedMat).destroy()