def parse_parameters(param_str):
    """
    Parse parameter string return by librenderman into a dictionary keyed on parameter
    index with values being the name / short descriptions for the parameter at that index.

    :param param_str: A parameter decription string returned by librenderman
    :type param_str: str
    :returns: A dictionary with parameter index as keys and parameter name / description for values
    :rtype: dict
    """
    param_list = param_str.split('\n')
    param_dict = {}
    for param in param_list:
        param_vals = param.split(':')
        try:
            param_index = int(param_vals[0])
            param_name = param_vals[1].strip()
            param_dict[param_index] = param_name
        except ValueError:
            continue
    return param_dict
