tree trunks are made by metaballs replicated along a path. The reason you see this is because there are metaballs that are too far apart in this area. Tho not a significant problem, if its something that you would like to fix, there are several options. 1 would be to try shrinking the tree's height thus reducing the distance between the affected metaballs which would minimize this "arc". another would be to duplicate the tree, reposition it very slightly and apply a transparency map that would only show a very small portion of the tree (the straight part) to the duplicate. just a couple methods, there are more. The tree trunks need additional features for editing. I hope corel add a "detail" and "bend" feature as well and a "knot hole" feature. luck BT