MagicaVoxel-Blender-Unity Workflow

Hi Trixie here….

We had a good break from the build cycle with the Text Adventure framework and since then have been making lots of fun headway on the main game in development Endless Elevator.

Endless Elevator is, as the name suggests, an endless runner style of game. It’s played in the vertical axis and follows the Good Cop as he scales the heights of an endless building shooting down the bad guys, climbing stairs, and catching elevators.

We have the main game functionality finished to a point so we started working on background objects and some cute little buddies for the Good Cop. It’s puppies…ain’t they cute!

This is not about the puppies though. This is about the workflow we have been using for creating assets using MagicaVoxel and making them game engine ready using Blender before importing them into Unity.

Lets start with MagicaVoxel. A 3D voxel editor that is free (no commercial license required) 8 bit and super awesome. Credits to the software are appreciated (e.g. “created by MagicaVoxel”) – like what I did there just like that! All the assets for the Endless Elevator have been made with MagicaVoxel. The walls, the floors, the furniture, and the characters.

First we model and then we paint in MagicaVoxel. For example this table lamp:

When we are done modelling and painting we export it as an .obj file that also produces a .png of the palette mesh mapping. It’s a bit like using the UV Unwrap in Blender but much harder to manually map or see.

Once we are done with MagicaVoxel if we want to optimise we import the .obj file into Blender. Blender is a terrific open source 3D modelling (and more) software. There is a trade-off here… we use Blender to lower the poly count on complex objects by using the decimate modifier. This modifier basically takes a parameter in your vertexes (like the angle between edges) and reduces the vertex count by simplifying the model. You see the problem with MagicaVoxel is that it created edges from a fixed point which can make lots of thin triangles.

Have a look at this model of the lamp imported into Blender:

You can see all the sharp angles of the triangles there. This is how MagicaVoxel works under the hood and it’s great for the internal workings of that program and is very efficient when working in that app but it sucks a bit for making complex models that you want to import into a game engine.

This is the Decimate modifier in Blender that we use to simplify this topology. We tell the modifier to take the Planar (faces) and simplify anything that has an angle under 25 degree.

We are left with something like this: (below)

This is much simpler and super easy for the game engine to understand and render.

The trade off here is that when you decimate all the vertices you lose your UV mapping for the paint work you might have done with MagicaVoxel. These are the limitations of working with awesome freeware. Sure they are awesome but if you shell out a few hundred (or less in some cases) for different Voxel modelling software you can get away with not having to work around these problems. But welcome to the world of no-budget game making. Hacking through the workarounds is part of the fun. Plus you actually learn a bit while you are working it out.

So in our game Endless Elevator we use a lot of small models (ie. not complex) and import them straight from MagicaVoxel and use their paint system and resulting exported image files for making the materials (albedo component). If we have more complex models that we want to simplify, like the walls and lifts in the surrounding building, then we import into Blender and do some optimising. Once the complex models have been optimised then we unmask them and paint the UV’s using GIMP. Next when they are imported into Unity we either add a material with the coloured UV mask we painted up or use Unity’s in built colour system for large areas.

There is another problem with using MagicaVoxel to make your game assets and that is on more complex models the “normal” of a face are often flipped the wrong way round. This one is kind of easy to spot and not that much fun to re-mediate. If you have a look at our character below you can see his shadow being projected on to the wall behind him.

Oops – he’s got big holes in him. You cannot see it on the model and it’s really only a problem if you are looking for it and using lots of hard lighting. In a 3D model each mesh forms a face and that face has two sides. In Unity’s default Shader only one face (the forward one) is rendered. So when MagicVoxel flips a few faces here and there (they are very small usually) you get these gaps that do not block the light in a shadow. It’s pretty hard to show in an image but what we have below is the model imported into Blender where we can expose the normals (the direction the face is facing!) and see the issue. In this image we have clipped the camera hard so that we can see into the cavity inside the model. Normals show up as light blue lines. You can see a few of them poking the wrong way into the center of the model instead of the outside. You can play around with the “flip normals” feature in Blender to fix these issues but it’s a lot of fiddling that frankly I have not had the patience or need to do yet!

So these are just a few of the issues and workarounds we use with this workflow – I hope you enjoy reading about it and if you have any questions feel free to comment 🙂

Trixie out.

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