In this lesson, you create a group of mr Proxy objects, and associate each proxy with an .mib file such as the ones you saved in the previous lesson. Then you assign each proxy a material from your mytrees material library.
  Open proxy_trees_start.max.
               The new scene features a rolling terrain intersected by a riverbed.
Create an mr Proxy object and associate it with an .mib file:
  Create panel and click  
  (Geometry). Open the Objects
               drop-down list, and choose “mental ray.” On the Object Type rollout,
               click “mr Proxy.”
            The proxy object you create can be of any size.

  Modify panel and rename
               the object Elm-Winter.
            
 Proxy File group, click
               the  
  browse button.
3ds Max Design opens a file dialog. Go to the \sceneassets\renderassets folder, choose elm1_winter.mib, then click Open.

 Proxy File group, set
               the Scale spinner to 0.1 to reduce the proxy to one-tenth
               its default size.

Copy the original proxy and change the tree types:
  Shift +move
               the proxy to the right.
 Object group, make sure
               Copy is chosen, then set Number of Copies to 3. Click OK.
  Select a copied proxy and
               on the  
  Modify panel, name it Elm-Spring. 
            
 Proxy File group, click
               the  
  browse button and use the
               file dialog to choose elm2_spring.mib.
            
  Select all four proxy objects
               and Shift+move them
               once, downward. In the Clone Options dialog, make sure Copy is chosen,
               then click OK.
  Zoom,  
  pan, and  
  orbit so you have a good
               view of all eight tree proxies, then  
  render the Perspective viewport.
Tree proxies with the same material
The tree proxies have different shapes and leaf densities, but their leaves and trunks are all the same color. In the next procedure, you will associate each proxy with a material you saved earlier in the material library.
Assign materials to the tree proxies:
 Material/Map Browser.
            
 mytrees.mat
               group, and drop this material on your selection.
3ds Max Design opens an Assign material dialog. On the dialog, make sure Assign To Selection is chosen, then click OK.

  Close the Material/Map Browser.
            
  Render the Perspective viewport
               once again.
Tree proxies after receiving materials from the material library
Now you have eight different types of trees that are ready to be multiplied and distributed across your scene.
  Close the Rendered Frame
               Window.