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Aldar

Procedurally generated plants and game environment in Unreal

Overview

Aldar was the junior year game project I worked on at DigiPen. I worked as technical environment artist and at times producer with a team of 10-20 teammates (the number fluctuated). There were 3-6 artists at different points. The project lasted for two semesters, with one semester of pre-production and one semester of production. Unfortunately, after the first semester we lost our director and a number of teammates, so the team was hard pressed to deliver a full 3D game. The goal was a Breath of the Wild inspired puzzle game, but we ended the production after making mostly the environment and some story/gameplay elements and moved on to other teams.

Overall, it was a lot of work and I learned a ton of techniques for vegetation and tech art in Unreal and with Houdini. I made all of the vegetation in the environment, most of which was procedurally generated; the floating islands, the clouds and skybox (which were pretty last minute), some of the environment effects, plus picking up a lot of extra texture and modeling work. The trees took a lot of iteration and were probably my favorite part of the project.

In-engine screenshots from Unreal.

Pre-Production

I began with exploring different ways to make trees and foliage cheaply with foliage cards, and use different distribution methods for populating an environment. Also spent a lot of time learning the grammar of L-systems to make variable trees.

Midgard’s megatree

Grove Tool

Exposed parameters:

  • Primitive
  • X/Y size
  • Count
  • Falloff

LOD Strategy

After studying some games with great foliage like Uncharted or Assassin’s Creed or Horizon Zero Dawn, I found some common tricks for having high-resolution foliage with cards and LODs.

Production

During the production phase, I used the systems developed during the first semester and created textures and models for a heavily procedural pipeline.

New Canopy

A big focus was the appearance of the foliage en masse of the main tree, because it would be popagated throughout the environment and almost always taking up a chunk of the viewer’s vision.

Fronds

The critical element for foliage is the cards - how big bushes of leaves are broken down into chunks of geometry with textures of leaves. Traditionally, a lot of games use the cross-bar method, which gives you a field of leaves from most angles:

However, I found using low-poly geo that follows the gesture of the foliage to work much better.:

Tech Art

As mentioned before, this project was a great vehicle for tech art. More techniques used here are documented over in Foliage Tech, such as normal resampling for subsurface effects or L-system basics.

Growth and Probability

The two main factors of variation in plants are growth and probability. With growth, you can export each stage in a plant’s growth as a unique model. With probability, such as using an L-system, you can generate similar but different variations of the same model

Procedural Generation

This shows the growth sequence in Houdini of the main canopy tree.