У меня в хелпе к СпидТри есть тутор как делать лес:
1 You will notice that the Spline you create actually exists above the ground surface. This is nessisary for the SpeedForest utility to work correctly.
2 In the create tab, select IDV software from the geometry pull down.
3 Click on Tree (v2.0) and click in one of the viewports. This will create a Speed Tree. (/Broadleaves/English Oak)
4 Import the EnglishOak_MD SPT file into the tree. (/Broadleaves/English Oak)
5 Go to the Modify Command Panel.
6 Expand the Size rollout. Change the size value to 500. Now, under the ".spt" Data rollout, hit Compute. This will resize your tree.
7 Under the Viewport display roll out, set the Tree Detail to Spike. This will make working with the scene with a lot of trees easier to deal with.
8 Now before we add the terrain to the SpeedForest utility, we need to colapse it to an Editable Mesh. It is required that your terrains are collapsed an Edible Mesh or Editable Poly. Select the terain and go to the modify tab. Right click on Editable Mesh in the stack and click Colapse All. Now we are ready to use the SpeedForest utility.
9 Under the 3ds max utilities click the "More..." button. Select SpeedForest from the list and click OK.
10 Expand the Objects rollout and click on the Pick Objects button. Select the tree you just created. You should see it appear in the list.
11 Increase the Object count to 100.
12 Increase the Collision radius to 50.
13 Under scale, decrease the min to .5. Increase the max to 1.5
14 Expand the boundaries rollout. Click on Pick boundary shapes button and select the splines that you drew.
15 Expand Terrain meshes and click on the Pick terrain objects button.
16 Click on the terrain in one of the viewports. It should now appear in the Terrain meshes list.
17 Click the Create Forest button under the SpeedForest rollout.
18 After a few minutes, 35-50 trees should be generated for the forest.
19 Select Direct01 and go to the modify tab.
20 Turn on shadows. From the shadow type pull down list select SpeedShadow. SpeedShadows are as fast as shadow maps, but include the detail of a ray traced shadow on opacity maps. This makes them ideal for using with Speed Trees.
21 Switch to the camera view and render the view. You should have a look similar to the following figure.