Using a process known as Photometry (a little different from photogrammetry), I scanned in these poison ivy leaves. Placed in a light tent, the light was angled at 5 different angles (1 for Sub-Surface Scattering), and photos were taken. These were then processed in Substance Designer using the Multi Angle to Normal Node. Then After Generating Roughness and Height, i added a few blends and finishing touches to polish the textures.
After this, i took the meshes into Houdini, and scattered them on a user controlled input mesh. The Amount of leaves, size etc is all controllable. The result is highly realistic Ivy Patches. (The Base Meshes are Megascans Assets.)