The new sculpting tool has been dubbed 'Mega Mesh' by the studio, and allows its team to work with multi-billion poly models. You can check it out in the video below.
According to Lionhead lead programmer Ben Sugden, Milo & Kate was designed to have a "hand sculpted feel but the softness and subtlety of realistic lighting". The studio wanted "bold shapes with areas of fine detail" in which it would "avoid hard polygon edges when objects are obviously placed onto of other objects, or when two objects are intersecting rather than nestling together naturally".
Sugden's overall aim was to create a "world to appear be a coherent, single whole, like one huge painting or sculpture".
However, Sugden told a behind-closed-doors audience at GDC that this objective created a major problem: an issue with scale.
"The current crop of sculpting tools are great for discrete models, but start to hit a wall when you hit very large polygon counts," he said in a talk entitled 'Modelling, rendering and lighting a world made of 100 billion polygons'.
"For example [industry standard tool] Zbrushworks brilliantly for characters, but as soon as you start to push beyond 10 million polygons or so, things really start to slow down. To give you an idea of scale, a typical level in our game - if we worked at roughly a 5mm texel resolution - would require around 10 billion quads."
The studio set about programming its own tool, which eventually became known as Mega Mesh. When Molyneux talks of Milo & Kate's tech being used to create "amazing new stuff" in future, we're guessing this is what he has in mind.
Sugden explained how studios conventionally model environment meshes - and the stumbling blocks this process creates.
"First you build a mesh in the modelling tool of your choice," he said, "Then you UV unwrap everything. And then you move to Photoshop or something for authoring textures, bumpmaps etc. We're all pretty familiar with this, but there's a problem: it means artists have to work first in 3D and then in 2D.
"Moving from 3D to image space means the artists jump from thinking about the shape of an object, to thinking about very fine surface details - such as 'let's apply a wood grain' - in one step.
"We felt this could easily result in models which look like triangle meshes [with] textures plastered onto them, rather than a good representation of the geometry.
"By contrast, character artists have more freedom to overcome this. Since we usually allocate relatively large budgets to character models, sculpting tools [to build environments] become viable."
"[Using sculpting tools] artists can work at any level of detail they wish, and can paint directly onto vertices. Normal and albedo maps are generally derived from the high polygon model, rather than painted independently.
"And when artists are modelling, if they want to increase the resolution they need for painting, they just subdivide the geometry.
"Since our world required a painted look we felt that to paint and sculpt our whole world would allow us to deliver on our art ambitions.... it seemed pretty obvious that we should be using a sculpting tool - so why isn't everyone already?"
Here, Sugden explained the problem with "scale" when using current industry standard tools - and how they can't handle those mega-high polygon counts.
"We've developed a tool which allows us to overcome these problems, enabling us to manage multi-billion poly models," Sugden explained. "It's the core of our pipeline and is called the Mega Mesh tool.
"It sits between the content creation tool producing the rough low-poly model and the sculpting package, enabling multiple users to work simultaneously through integration with version control.
"We work around the 10 million poly limit [problem] by allowing the user to select regions of the world using a window. So with a large selection window, you edit the world at a lower resolution, and with a smaller window you have finer detail available. And finally the tool ties the pipeline together by coordinating the build process."
You can see the results of Lionhead's new tool dotted around this page and in the video above, which Sugden used to accompany his GDC talk.
Regarding the video, Sugden has qualified it was "running on a stock Xbox 360 at 30fps - although the video capture has made things look choppy". He added that the tech "is totally viable on either an Xbox or a PS3". One love.
[Thanks to CVG reader MattyR95]
Read Ben Sugden's full GDC presentation sheet (in all its technical glory) through here.