Rendering Tutorials > Reducing Complexity in Your Renderings > mr Proxies >
Using Object Paint to Distribute the Trees

Now that you have your tree proxies properly defined, you need a way to instance them multiple times and distribute them across your terrain. You can do this by using the Object Paint feature, which is new to Autodesk 3ds Max Design 2012. Object Paint lets you paint objects onto other objects: In this lesson, you will paint proxy trees onto the terrain object, Plane01.

Set up the lesson:

- Continue from the previous lesson or open 8_trees.max.

Choose the trees with which you will paint:

1. If the ribbon isn’t already open, then on the main toolbar click (Graphite Modeling Tools). Click the expand/collapse icon until you can see the full height of the ribbon.
2. On the ribbon, click the Object Paint tab.
3. On the Paint Objects panel, click (Edit Object List).

   3ds Max Design opens a Paint Objects dialog.

4. On the dialog, click Add.

   3ds Max Design opens a Select Objects dialog.

5. Click and Shift+click to select all eight tree objects, and then click Add.

   The grove you paint in this lesson will be an eclectic one. Another time, you might want to choose only spring trees, for example, or fall ones.

6. Close the Paint Objects dialog.

   Now you are able to paint the trees onto the terrain. By default, the Paint Objects tool uses the first object in the set you selected.

Set up the Object Paint tool:

1. On the Paint Objects panel, choose All, Randomly from the drop-down list.

   When you paint, the trees will appear in random order.

2. Also on the Paint Objects panel, open the Paint On drop-down list and choose Selected Objects.
3. On the Brush Settings panel, set Spacing to 40.00 units.
4. Also on the Brush Settings panel, open the Align drop-down list, and turn off Align To Normal.

   We want the trees to grow vertically, not to lean wherever the terrain is not flat.

5. The right-hand side of the Brush Settings panel has three groups of controls: Scatter, Rotate, and Scale. In this tutorial, we don’t use the Scatter tools, but do make adjustments to the other two groups.

   In the Brush Settings panel Rotate group, click the drop-down arrow next to the Z coordinate field, and in the drop-down list, turn on Random Z.

   When you paint, the trees will have a random amount of rotation about their vertical (Z) axis.

6. In the Brush Settings panel Scale group, make sure axis Lock (Uniform Scale)) is turned on, then open the Scale Type drop-down list, and choose Random.

   After you choose Random, the Scale group shows a range of values for the axes; because Axis Lock is on, you can change only the X axis values.

7. Also in the Scale group, set the minimum X value (on the left) to 60 and the maximum X value (on the right) to 160.

   The trees will vary in height and girth from 60 units to 160.

   Now you are ready to begin painting trees.

Paint the proxy trees:

1. Select the terrain object, Plane01.

   Remember that Object Paint is set to paint onto the currently selected object.

2. Maximize the Top viewport, and click (Zoom Extents Selected).
3. On the Paint Objects panel, click to turn on (Paint).
4. Hold down the mouse button as you drag over the terrain object. 3ds Max Design adds copies of trees to the scene. The trees are at least 40 units apart.

   You can paint the trees densely together, but on the near bank of the stream, avoid painting directly in front of the camera’s line of sight.

5. Minimize the Top viewport, then activate the Camera01 viewport, and render the scene.
   TipIf any of the trees appear to be floating above ground level, then on the Paint Objects panel, set the Offset value to a negative value; for example, –3.0.
6. One good feature of Object Paint, is that you can preview the scene with renderings before you commit.
   - If you are not happy with the results, click (Cancel).

     3ds Max Design removes the trees you painted, allowing you to start over.

   - When you are happy with the results, click (Commit).

     3ds Max Design adds the trees to the scene, as copies of the original tree proxy objects.

     If you like, experiment with other options, such as painting with only trees from a certain season, as we suggested earlier, or changing the range of Scale X to paint a greater (or lesser) range of variation in size.

Save your work:

- Save the scene as my_forest_painted.max.

  You can compare your work with a finished version of this scene, proxy_trees_final.max.

Summary

When you render with the mental ray renderer, mr Proxies are a useful way to create a large scene with many instances of a similar object. While mr Proxy objects cannot be edited directly, they offer the advantage of freeing up memory and speeding up render time.