cannot find rgb info in placeholder

Hi, 
Thanks for sharing this work!

in the paper, you said, the input is six channels, x, y, z, r, g, b.
but I find in the code, it's 
```
   pointclouds_pl = tf.placeholder(tf.float32, shape=(batch_size, num_point, 3))

```
it seems the input is three channels?

Thanks!