Distance based tessellation in UE4 for virtual reality applications

cageclaypool

For those of you who've worked on assets for VR games, you may know that normal maps don't appear properly when trying to simulate large details. it's difficult to explain to people who've never used a VR headsets, but your binocular vision essentially makes normal maps look very fake unless viewed from head on, so they have very limited applications. Because of this human models tend to look pretty fake once you get near them. For anyone who attended GDC, you may have visited the Sony booth and spotted the PSVR subdiv SDK booth. Essentially it's an SDK that is available to Playstation developers, that allows objects to subdivide the closer you get to them. This is distinctly different from LODs as the whole mesh does not subdivide, only the closest polygons. In VR it's an incredibly convincing illusion, as you can get as close as you want to a mesh and it will continue to get more detailed the nearer you are.
Is there any way to replicate this technology in UE4? I'm working on a vr game and I would like to use this, but I have no current plans to develop for the PSVR. Iv'e seen examples of distance based tessellation in UE4 for terrains, but it has a lot of tearing and other problems

Sorry for the poor image quality, I just grabbed some photos at the booth, and couldn't find any resources for this technology online. I did not make any of the art assets I am posting:

Probably the most impressive part of this technology is the fact that the input mesh is very low poly, and the rest of the details are generated using height maps. In the following images, the green wire-frame is the input mesh, Notice how the spheres in this model are only 24 sided , meshes:

As you can see it's a very effective solution, but this technique isn't meant to be used on every model, It only appears once you get very close to the mesh. I also have no idea how this works on non-organic shapes. I think the most useful application for this technology is to subdivide human models once they get very close to you.

anyone know a good way to do something like this in UE4? Would it be possible to accomplish this with only a material, or will it require some coding?

cageclaypool

I should probably mention, that I'm pretty confident this is possible. I'm more concerned  if 90 fps is still doable with this technique

LTS3D

It is possible. You need to generate the distance between the object position and the camera position, then use that as a falloff of sorts for your displacement multiplier.

Obscura

Thf fps would really depend on the videocard, and the 90 would be probably hard to achieve on VR.

To make the distance falloff, you would need to take the camera position and world position, and measure the distance between them (since pixel depth doesn't work in non translucent materials), then divide by the desired distance.  I would put a clamp on this and plug it into an alpha of the lerp, and put values for min and max sobdivision. Then this whole thing would go into the tessellaion multiplier. Maybe you would need to apply the same fallof on the displacement itself aswell.

ZacD

At GDC Epic mentioned they added Pixars open subdiv to the engine, so I'm kind of expecting this to be an integrated feature in 4.16

Source: https://youtu.be/K6tRt7c2elU?t=4101

MatiasP

I think this is what you're looking for.

http://youtube.com/watch?v=_Xmxt1wv1SE