Authoring grass using normal mapping tools2
thedenrei posted in Uncategorized on January 21st, 2007
I’ve been working more or less consistently on the project our main page so sparingly alludes to.
The main bits of the game come from one of Tony’s wildly elaborate and fascinating dreams mixed with Willow (the movie), Zelda64 and a mis-communication of one my brainstorm ideas at our initial design meeting.
Environments have been my focus lately. The persisting lack of an animation system makes character design feel kind of cramped and lackluster.
I once read an article about the creature fur in Black and White 2. I remember thinking it would be a nice technique for things like plants and grass and I’ve since noticed it used in games like Shadow of the Colossus in those very situations. I’m not sure what kind of workflow those guys used to create their fur and grass, but I’ve wondered about using normal mapping tools and some by-hand work to acheive the same results. Recently I went ahead and tried it out, and I think the results are pretty good for a first attempt.
The technique is plotting dots of color on many layers of transparent polygon planes. When you get enough layers and view it from a proper radius, it looks like strands of whatever. The pictures will better describe what I mean:
To create this, I started by using Maya’s PaintFX tools to quickly generate some polygonal blades of grass. I converted these to geometry shapes, and then created 18 rectangular faces of equal size stacked upon one another and evenly spaced out. The planes created a box that encapsulated the blades of grass. After laying out the UVs of the planes, I merged them into a single shape and calculated a normal map with the grass as the source mesh and the planes as the target mesh. Because I kept the search radius very very low for each face, the normal map came up empty besides where the blades of grass had intersected the faces. I then colored the UVs for each face in photoshop by had to get a gradient of dark green to white as the planes go from bottom to top. Anywhere the normal mapping tool wasn’t able to get a result I made transparent. I hope this makes sense, I kind of feel like it won’t as I compose this. Usually in the game, you’ll only see this grass from the top, so the side angles that get all split apart will be avoided.
We’ve become very elaborate and official with our project management. We use a system called “SCRUM”, perhaps you’ll be able to read up about it in Gavin or some one’s blog… I don’t understand it all too well, really. I’m just there because I have good (maybe I should just say “better”) handwriting for the index cards. I think its meant for much bigger groups working on much bigger projects, but it helps us communicate and stay disciplined about exactly what we are doing so we don’t work on all kinds of randomness forever.
RockinOutMan has been Rockin the drift trank on the PS3 demo of GranTurismo using a Logitec MOMO via USB the entire time our current project has been in development. There was a breif period where I could bank scores higher than his, but lately he has been getting REALLY good, and has hopes for the top spot on the online rankings. Currently a man named SlighteyCyrus dominates the drift boards. We hate this man, but are quite sure he lives in the apartment down the hall from us. Note the spare MOMO in the lower right.
