How can I properly orient custom leaves with a Particle System modifier? In trying to replace Sapling 2D leaves with custom ones, I struggle to orient them properly. Setting the Tangent value to 1 in the particle system doesn't have any effect (bug ?).



The new leaves in this blend are in the right plane and their bases touch the branches. It must remain like that, but the new leaves should grow in the same direction as the old one (at the moment it's random). If you select one of the old leaves's face and choose "normal" for the orientation, you can notice that the x and y axis follow the sides of the old leaf, so the orientation information is in the mesh. But how can I get it to influence the particles?


The base of the new leaf must touch the branches because the tree will be in the foreground.
The orientation must follow the original leaf's one.
The whole foliage must be easily editable and form one mesh (to be able to make instances of it). For that, the current solution is to use a particle instance modifier. The answer can use something else, but it must have the same convenience (fast because having each leaf in one object makes blender slow at 2000+ leaves and easy to modify : modifying one leaf mesh modifies the whole foliage)
You could use Duplifaces. When the sapling addon creates leaves, each rectangular leaf is a single face (hex leaves are two faced).

Create your custom leaf and then make the leaves object a parent of your leaf. In the object properties for leaves turn on Duplifaces.



Now your custom leaf will be duplicated at the location of each original leaf. The object centre of your leaf will be at the centre of the original face and will be rotated to match the rotation of the original single poly leaf. Modifying the original leaf will adjust every leaf to match. The original poly leaves won't render, just your custom leaf.



To speed up the viewport you can add a decimate modifier to the leaves object to reduce the amount of visible leaves.