The world's greatest virtual concrete slab
Yes, we're talking about a concrete barrier of the sort that you'll find lining highways all across the country at this time of the year. Also known as a Jersey barrier, these simple, stark structures are strewn liberally throughout the mid-apocalyptic New York cityscape in Crysis 2, providing cover and fortifying certain areas. You might not know it, and you almost surely didn't expect it, but these flat concrete blocks are one of the major targets for enhancement in the DirectX 11 upgrade to the game.
Here's a look at the DX9 and DX11 versions of the Jersey barrier. Rather than resize these first few screen shots, I've cropped them to provide you with a pixel-for-pixel capture of the game's imagery.
You can see that there's not much visual difference between the two. The biggest change is the little "handles" atop the slabs. In the DX9 version, they're flat and just textures. In DX11, they appear to be real structures protruding from the top of the barrier. I think there may be higher-quality textures in use in DX11, but some of the difference there may be the result of the fact that I haven't duplicated the camera position precisely between the two shots. Whatever the case, the visual improvement when moving from DX9 to DX11 is subtle at best.
However, in the DX11 "ultra" mode, the handling of this particular object takes up a pretty good chunk of GPU time during the creation of this frame. Why? Well, have a look at the output of one of the most time-intensive draw calls:
Yep, this flat, hard-edged slab is one of the most highly tessellated objects in the scene. The polygons closest to the camera are comprised of just a few pixels each. Further from the camera, the wireframe mesh becomes a solid block of red; there, we're probably looking at more than one polygon per pixel. Those are some very small polygons indeed.
Let's move around and have another look at the same barrier from the side, so we can get a cleaner look at its geometry.
These barriers a strewn all over the streets. Let's take a look at another one from a different part of the game.
Yes, folks, this is some truly inspiring geometric detail, well beyond what one might expect to see in an object that could easily be constructed from a few hundred polygons. This model may well be the most complex representation of a concrete traffic barrier ever used in any video game, movie, or any other computer graphics-related enterprise.
The question is: Why?
Why did Crytek decide to tessellate the heck out of this object that has no apparent need for it?
Yes, there are some rounded corners that require a little bit of polygon detail, but recall that the DX9 version of the same object without any tessellation at all appears to have the exact same contours. The only difference is those little metal "handles" along the top surface. Yet the flat interior surfaces of this concrete slab, which could be represented with just a handful of large triangles, are instead subdivided into thousands of tiny polygons.