Unreal Engine - PCG - Book Row Stacker
Procedurally generating a row of books in Unreal Engine using PCG is fairly straightforward, but handling gaps and calculating lean angles was a fun challenge.
Books 3D Model:
https://www.cgtrader.com/free-3d-models/interior/house-interior/books-collect
I used Shape Grammar because I wanted to stack rows with random books of different thicknesses. To achieve this, I needed to generate the grammar rule procedurally based on the books added in the graph's "Books" parameter.
PCG_Bookshelf_CalcLean Graph
This graph loops through all points and calculates the lean angle for each based on its gap distance.
To find the lean angle, I first needed the collision point of the leaning book against the previous one. I used the GetRaySphereIntersection function to determine this point.
In RaySphereIntersection, the book’s height is used as the sphere radius by default. However, if the previous book has a steep lean angle, this produces incorrect results because the bottom of the previous book may intersect first.
To fix this, I added another step to check for bottom contact.