code: public void setMaterial(GVRMaterial material, int passIndex)
      {
          if (passIndex < mRenderPassList.size())
          {
              mRenderPassList.get(passIndex).setMaterial(material);
          }
          else
          {
              Log.e(TAG, "Trying to set material from invalid pass. Pass " + passIndex + " was not created.");
          }
      }
docs: Set the {@link GVRMaterial material} this pass will be rendered with.
  
  @param material
  The {@link GVRMaterial material} for rendering.
  @param passIndex
  The rendering pass this material will be assigned to.