Carrara put those things in the appropriated size... the problem here is that when you add a tree using the Insert menu, the tree will be puted in the middle of the scene.

First, try to start with a MEDIUM scene (when ou hit new document), this way will be more easy to see the objects.

Add your terrain and shade it. Now time to add a tree: use the insert menu, and your tree (plant) will be in the middle of the scene, sometimes under the terrain, so you will need to move it to a better place.

But here the secret is to use the Medium preset scene, if you use Large, your tree will be very small and hard to move around.

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