Update README

* Rearrange README to place "Pre-trained models from SIGGRAPH'18 paper"  before "Running the model on a single image pair"
* Add note to indicate that model must be downloaded before running `mpi_from_images.py`

README.md

@@ -57,6 +57,11 @@ contains a ground-truth target image `tgt_image_*.png` and the synthesized image
 `output_image_*.png`. The script will output a text file summarizing the metrics
 inside the folder FLAGS.result_root.
 
+## Pre-trained models from SIGGRAPH'18 paper
+
+Our pre-trained model can be downloaded into the `models` subdirectory by
+running the script `bash scripts/download_model.sh`.
+
 ## Running the model on a single image pair
 
 To run a trained model on a single image pair to generate an MPI, use
@@ -67,15 +72,12 @@ between the images.
 You can find example input stereo pairs and command lines for generating results
 in the `examples` directory.
 
+(You must first download the pretrained model or train your own model and place in the `models/` subdirectory)
+
 ## Reference examples and results
 
 For reference, you can find additional example input stereo pairs, as well as corresponding output multi-plane images and view synthesis results used in the paper in this [Google drive link](https://drive.google.com/open?id=1CZGJxRl0GK0js0MbL7cn7tHtdRrtnjOB) (772 MB).
 
-## Pre-trained models from SIGGRAPH'18 paper
-
-Our pre-trained model can be downloaded into the `models` subdirectory by
-running the script `bash scripts/download_model.sh`.
-
 ## RealEstate10K dataset
 
 We have released the [RealEstate10K dataset](https://google.github.io/realestate10k/) suitable for training and testing the MPI model. Note that due to data restrictions, this is not the same version used in our SIGGRAPH'18 paper. However, we are working on updating the results using this public version.