How can I add a seasonal flare to my trees? – Unity

Symptoms

I would like to add a bit of seasonal flare to my trees added via the Terrain paint widget. The trees are not placed as GameObjects in the hierarchy.

Cause

There is not a function to swap between tree prefabs.

Resolution

Unity Terrain exposes the Tree instances using the array Terrain.treeInstances. Every Tree instance included in this array has a property that stores the tree Prefab configured in the Terrain settings (prototypeIndex).

The tree Prefab is updated automatically by changing this value.

TreeInstance[] currentTreeList;
TerrainData terrain;
int springTreeIndex;
int fallTreeIndex;
bool season;

void ChangeSeasons ()
{
    // The currentTreeList array must be at least terrain.treeInstances.Length in size
    System.Array.Copy (terrain.treeInstances, currentTreeList, terrain.treeInstances.Length);
    if (terrain.treeInstances.Length == currentTreeList.Length)
    {
        for (int tcnt=0; tcnt < currentTreeList.Length; tcnt++)
        {
            if (season)
            {
                if (currentTreeList [tcnt].prototypeIndex == springTreeIndex)
                    currentTreeList [tcnt].prototypeIndex = fallTreeIndex;
                }
                else
                {
                if (currentTreeList [tcnt].prototypeIndex == fallTreeIndex)
                    currentTreeList [tcnt].prototypeIndex = springTreeIndex;
            }
        }
        terrain.treeInstances = currentTreeList;
        season = !season;
    }
}

More Information

http://answers.unity3d.com/questions/521056/access-terrain-tree-material-from-script.html

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