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Sunday, December 17, 2017

Making the Citadel

We just put up a video of how the Magic Citadel demo for UE4 was built:

The demo is not available yet, we are still working on the game-side of it in UE4, but the Citadel model is pretty much complete at this point. I would like to cover a couple of aspects that I find interesting from this experience.

A question I often get is why use voxels at all. I usually point at the obvious bits: If you want to do real-time constructive solid geometry (CSG) pretty much anything else is too slow. CSG is what allows to create game mechanics like harvesting, tunneling, destruction and building new things. Also, if you are doing procedural generation of anything that goes beyond heightmaps, voxels make it much easier to express and realize your procedural objects into something you can render using traditional engines like UE and Unity.

What I rarely say is that once you work with voxels, your mind changes. I let people figure this out by themselves, I do not want to be that weird guy saying you really need to try LSD. You change because you begin seeing your entire project as a single fabric of content. You feel more like you are working on a canvas. There is no difference between a tower roof versus terrain you have terraformed. It is a really distinct feel, which cannot be explained rather experienced.

If you have developed for UE4 or Unity before, think of how you would approach a project like this Citadel. While it is possible, you would be building out of a myriad of objects placed in your scene. You would have an object for the terrain, static meshes for the towers, walls, even the rocks making up your cliffs would be a bunch of instanced meshes clearly intersecting each other. Simply put, there is no canvas, instead, you have a collection of things.

If you want to have large organic shapes, like a massive spiral tower that slowly unravels over hundreds of meters, you would need to carefully plan how to deal with all this unique geometry. The image below shows an example of this from the Citadel:

It gets messy. This often leads to not having unique geometry at all, as it is too much trouble. It is unfortunate. Unique geometry can take your content to a whole new level. Once you have experienced it for a while, going back to the traditional instance-based approach is immersion breaking, at least it is for me now.

When you build out of individual small pieces, even if they have LODs of their own, their agglomeration cannot be trivially condensed into single objects that will efficiently LOD. Serious consideration needs to go into which objects you use to build the world, how large they can be, how you can reuse them and create cheap variations of them. All this planning takes a lot of work and mostly, a big deal of experience.

This is why it takes a Triple-A team to produce complex scenes and rich open worlds. Even when there is plenty of very talented artists out there, the slew of tricks you need to apply remains a veiled, mysterious art. We should not need GDC talks. The current state of the industry is as if Microsoft Word would limit the kind of novel you can write with it, and only those versed in Word's options and macros were able to create compelling fiction with it.

As I see it, it is really about the "fabric" that makes the virtual world. Once it becomes an organic canvas, you can automate tricks like LODs, culling and visibility sets in simple, robust ways. Let the computer do the hacks for you.

The other advantage of developing a virtual world as it were a canvas, is that your workflow becomes closer to what you experience working in Photoshop, versus the Maya-Blender experience. This is one of my favorite bits in the video above, it starts around the 2:54 mark. The artist first defines the basic volumes and then continues to refine them. I find this very intuitive and close to how people create in pixel-based systems like Photoshop.

Talking about artists, this Citadel project was possible thanks to Ben, who became part of the Voxel Farm team early this year. The amount of work he was able to put into this Citadel is incredible, as is the quality of his work. Ben caught everyone's attention as a player-builder in Landmark, under the Ginsan alias. Here is one voxel beauty he created back then:

Screenshot from Landmark (SOE/Daybreak)

A true Renaissance man, Ben also created the superb music for the video above. He often tweets about his progress in new Voxel Farm projects, if you are curious about what he is working on, make sure to follow him