Like this Screenshot - 7818cd8e88b52540250c36d7159f9a65 - Gyazo what the do in Lumber Tycoon is when you hit the tree the Dark Cut Area the Material is changed from the Bark of the tree to black to look like its cutting
Like this Screenshot - 7818cd8e88b52540250c36d7159f9a65 - Gyazo what the do in Lumber Tycoon is when you hit the tree the Dark Cut Area the Material is changed from the Bark of the tree to black to look like its cutting