convert method 
    
      
Map<String, dynamic>
convert(
 - dynamic materialsInfo
) 
    
    
  Implementation
  Map<String, dynamic> convert(materialsInfo) {
  if (options == null) return materialsInfo;
  Map<String, dynamic> converted = {};
  for (final mn in materialsInfo.keys) {
    // Convert materials info into normalized form based on options
    final mat = materialsInfo[mn];
    Map<String, dynamic> covmat = {};
    converted[mn] = covmat;
    for (final prop in mat.keys) {
      bool save = true;
      dynamic value = mat[prop];
      final lprop = prop.toLowerCase();
      switch (lprop) {
        case 'kd':
        case 'ka':
        case 'ks':
          // Diffuse color (color under white light) using RGB values
          if (options != null && options!["normalizeRGB"] != null) {
            value = [value[0] / 255, value[1] / 255, value[2] / 255];
          }
          if (options != null && options!["ignoreZeroRGBs"] != null) {
            if (value[0] == 0 && value[1] == 0 && value[2] == 0) {
              // ignore
              save = false;
            }
          }
          break;
        default:
          break;
      }
      if (save) {
        covmat[lprop] = value;
      }
    }
  }
  return converted;
}