untitled city defense game: graphics and multiplayer

Quick update for the live review. I didn’t get terrain working fully over the weekend, but I did figure out texture arrays and blending in Unity shaders, which is pretty cool!

Going to post here to wrap up March. I did not have a very productive second half of this DK30. I have made a lot of progress understanding shaders in Unity, which I’ve wanted to tackle for awhile now. I haven’t gotten terrain textures working yet, though. I think I’m close, so I’ll make a push to do it this weekend, and continue posting occasional updates here if the site stays up after March.

Some background first. My game is a colony-defense citybuilder somewhat in the tradition of They Are Billions. It takes place on an irregular grid of cells. Game logic uses ‘cell’ as the fundamental unit of positioning; you order units from cell to cell, select a cell to build buildings, and so on. Each cell can hold ~2-4 buildings. (Most RTS games aren’t like this, of course. It’s a new thing I’m trying out!) I’m working in Unity.

Here’s what it looked like at the start of March, with abstract polygons and no visuals for buildings: My goal for the first two weeks of this DK30 was to upgrade the graphics. Specifically, I wanted to draw terrain with textures and elevation, and add some sort of building visualizations.

I generate the irregular cell grid as a Voronoi diagram. Turns out rendering heightmaps is not straightforward on irregular terrain! Here are the things I actually managed in the first two-and-change weeks:

• Wrote “subdivision” tools that takes triangles or quads and fill them with smaller triangles that are approximately evenly spaced. Specifically, I wanted to subdivide while controlling the number of vertices produced on each edge. I wasn’t able to find anything about that specific problem online, so I rolled my own. It assumes at least two edges of the quad or triangle have the same vertex count, but that’s enough for my purposes. I also updated my mesh generation tools to be generic in vertex data (no more dummy UV coordinates!) and to allow me to reuse vertices when connecting different meshed regions.
• Wrote a DCEL implementation to track connections on the Voronoi cells. I would highly recommend this, by the way. My first attempt used a simpler data structure, but it ended up being harder both to use AND to instantiate! Using the DCEL has been a dream.
• Adjusted Voronoi vertices to lengthen small edges, which had been causing several annoying issues. I used the approach described here by the excellent Amit Patel. I prefer the boxier shapes that pure Voronoi cells tend to take, but we’ll go with this system for the time being.
• Wrote cubic interpolation tools to make smooth cell transitions. I did not expect to download a linear algebra library to do elevation rendering, but it looks like that’s how you do cubic interpolation, so here we are! I also ended up writing a polynomial class and auto-differentiator so I could specify polynomials and fit them automatically. This is not the most CPU-efficient way to do heightmaps, but it was a lot more fun than differentiating by hand and then typing in the equations. It also allowed me to iterate quickly on different polynomials and constraints.

Now, here’s the result: No textures and no building graphics, but so it goes! It felt really good to get this far, especially in the face of a pile of unexpected complications. I’m afraid I don’t love the end look, though - I’d like it to feel a lot more natural, without such obvious edges and corners. I had hoped cubic interpolation would handle some of that, but it appears to have mainly just rounded the edges a bit.

Some ideas I may investigate later:

• Increase the spacing between the flat parts of cells.
• Adjust vertices after the fact to ‘erode’ them into more natural shapes.

For now, though, I’m going to adjust my goals for the second half (“half”) of my DK30: textures by the end of week 3, and rudimentary building visualizations by the end of March. I’m also going to try to make smaller, more regular updates here.