///
/// Query the content instance for the value of a given named parameter.
/// If you do not support this parameter, call the base class.
///
/// Name of the parameter
/// IConvertible. Note that you can’t directly cast from object, instead you have to use the Convert mechanism.
for example:
var t = renderMat.GetParameter(“transparency”) as IConvertible;
var d = Convert.ToDouble(t);