Inspecting a RenderMaterial and its parameters

written by Nathan 'jesterKing' Letwory

The RenderMaterial is the class that represents materials in Rhino. The same class is used for all different materials that are provided by Rhino, and even non-Rhino materials are supposed to implement this.

The main way to access a RenderMaterial parameters, the properties that determine the visual appearance of the material when rendered, is through the methods GetParameter and SetParameter. And therein also lies the problem.

To be able to successfully access the parameters you need to know the names of these parameters. But by itself there is no obvious way how to find the names out. And each material type will have its own set of parameters.

<<inpect render material parameters.*>>=
import scriptcontext as sc
import clr

import System.Xml as xml

rms = list(sc.doc.RenderMaterials)

<<loop over each rm and inspect>>

For each material we are going to access the Xml property. This property provides a description of the material in question in XML-form. In this XML document we are going to look for the <parameters> tag. This is essentially where all the parameters of a material are expressed.

On each iteration of the loop we are going to create an XML document and load the XML provided by the RenderMaterial into that document. Then we can look for the parameters tag.

<<loop over each rm and inspect>>=
for rm in rms:
    print('material:', rm.Name)
    rmdoc = xml.XmlDocument()
    params = rmdoc.DocumentElement.SelectSingleNode('parameters')
    <<loop over all parameters and print>>

Now that we have this node <parameters> we can iterate over its children, and show the information we have learned. The name of each child node is the name of the parameter we need for proper usage of the GetParameter and SetParameter methods.

We can start by getting the first child, and then continue by asking each one for its next sibling until we got none.

To understand what data type each parameter is we ask for the type attribute. This tells us whether a parameter is a boolean, or a string, and so on.

<<loop over all parameters and print>>=
param = params.FirstChild
while param:
    param_type = param.GetAttributeNode('type')
        param_type = param_type.Value
        param_type = 'N/A'

    print('parameter', param.Name, 'is a', param_type, 'with value', param.InnerXml)
    param = param.NextSibling

The generated script is in the repository here