The leaf geometry is generated using the "Trace" node in Houdini. The alpha cards I used here are from Quixel Megascans, but any alpha card map will work fine. I loop through each leaf, remesh, UV based on the original map location, then centre the pivot.
I used Side FX Lab's "Quick Tree" node to try to get a more realistic distribution of points to copy my leaves on to. I get the centroid of each generated leaf and blast away all of the Quick Tree's geometry. I then copy my leaves to all of the points.
I then ran a Vellum simulation to get natural pile up, crinkles, and folds in the leaves as they collide.
Using the last frame of the simulation, I blast away all leaves that haven't hit the ground yet (outliers) and feed the result into the "Mesh Tiler" node.
I colour the front and backsides of each leaf to make a mask for use in Designer and bake it out. The backing ground plane is added back in to fill the holes and the original Megascans material maps are applied and transferred via the bake.
In Substance Designer the baked mesh data from Houdini is read and applied for the final material. The colour ID map allows me to manipulate the values for the backside of each leaf. Dirt and dampness layers are added.
The final map outputs of the material.
Feeling inspired by fall! The idea of this piece was to see how effectively I could use photo scan data to make realistic scatter materials with Designer and Houdini simulations.