Shifty Geezer said:
Regards article, I did like the Displaced SDS! Not sure how well it'll work in motion using a texture to specify geometry as the texture will warp with UV's, causing bending structures that should remain inflexible and the like. It'd be nice to hear Laa-Yosh's opinion on how useful this'll be for things like characters or inanimate tyres and scenery and bits. Maybe KZ's tyres aren't in the realm of impossibility?
We're heavily displacing EVERYTHING here
It works well enough in most cases, because the displacement is always relative to the surface, along its normal - so when you bend a limb or something, the displacement 'moves' with the skin.
(There are methods to displace along other directions and not just the normal, but it's hard to get proper data for that... so most people stick to standard displacement.)
You have to be careful not to go too far with it though, like, displace a horn or such a big thing. First it'll kill the accuracy of your map, because the maximum displaced distance defines the amount of elevation between two intensity levels (I don't expect games to use floating point maps for this in the near future...) and second, larger features
can get distorted when the underlying surface is deformed by a skeleton.
Shameless plug... here are two characters from our recent work:
http://hardwired.hu/img/wg/2/623/Warhammer_Mark_of_Chaos_52.jpg
You can see here the original geometry in a black wireframe, overlayed on top of the displaced surface (this is an ambient occlusion pass so no textures or shading here).
http://hardwired.hu/img/wg/2/623/Warhammer_Mark_of_Chaos_51.jpg
Here you can see how much silhouette detail we can get with displacement; but also that all the larger features like horns are modeled in, and that the polygons are laid out to support animation (and they're also quite uniform to make the Zbrush painters' job easier).
http://hardwired.hu/img/wg/2/623/Warhammer_Mark_of_Chaos_47.jpg
http://hardwired.hu/img/wg/2/623/Warhammer_Mark_of_Chaos_48.jpg
Also note that we're using Pixar's Renderman for these, which tesselates everything adaptively to micropolygons smaller than a final pixel. IIRC we've been using a shading rate of 0.5 which means ~4 micropolygons per pixel. The tesselator in Xenos probably won't be able to create such a dense mesh for everything in the scene... so like, you could do up to 4 tires, but go with lowpoly characters and enviroments
Seriously, I expect that developers will probably have to budget their resources properly and use the tesselation/displacement for some key elements in a scene. Like the T-rex in King Kong? Although it didn't look displaced to me, 'only' tesselated with smooth curved silhouettes.
Another interesting info is that that creature in the slides has been made by Bay Raitt, if I'm right here; he has modeled the face and most of the expressions for Gollum in the LOTR movies and is working at/with Valve for more than a year by now...
PS: you can watch the whole animation here:
www.digicpictures.com
