Laurens Corijn » Tips

Vertex Blending Snow

Laurens — Tue, 01 Dec 2009 16:26:09 +0000

Due to an ongoing thread at the Polycount boards about the snow and ice of Uncharted 2, I replicated Paul Greveson aka MoP’s vertex blending material in Unreal.

This is my result:

The tank tracks are another type of blend, this one’s about the snow on the ground.

I was asked to post my node layout on my blog, so here goes:

The base mask for snow coverage is calculated by using the Red vertex color channel (you can easily paint onto one channel only in UDK, great feature!) and a heightmap. These are combined together to create a transition effect with the heightmap, where the vertexcolors fade out. Clamped at the end to prevent extreme values, just for safety.

Using the Green vertex channel, we calculate a varying number for the mask’s hardness. 20 is the ceiling value, a 1 is added to prevent powering to 0 (bad). The invert on the vertex color is just to make sure the default value is hard (default vertex color is 1,1,1,1).

Both groups are combined by powering the raw mask to the hardness value, adjusting the contrast. Clamped for safety, though technically not necessary since we’re only powering a value of max 1to20,resulting in a 1 anyway.

The mask is used on 3 LinearInteroplate nodes, to blend between snow and non-snow diffuse, spec and normals. Since I had the heightmap anyway, I just used it for a quick parallax effect on the diffuse (I should apply it to normals as well…).

Total material. Nothing too complex, only 63 instructions which really isn’t expensive.

I recommend doing this in UDK only, since painting vertexcolors is incredibly easy there.

Normal baking and 3DS Max Tangent basis

Laurens — Tue, 15 Sep 2009 22:10:30 +0000

During my Skorpion SMG project, I did a lot of normalmap baking. The baking itself really is the most tedious process for me, reaally slows me down a lot, even compared to UV’ing which a lot of people find horrible (I think it’s quite easy if you have TexTools and Unwrap Tools).
Every cage needs an hour of tweaking in my case (I group things into 4-5 big objects) and then still requires overpainting and fixing of normalmaps in Photoshop. I did find out a few things while baking in Max and xNormal:

Max uses an incorrect tangent basis to compute the normalmaps from. This results in the maps not working 100% correctly when viewed realtime with a shader. They do look ok when rendered, but that’s pretty useless for a game-artist.
xNormal does use the correct tangent basis, but is a bit tricky to set up. Biggest letdown was the lack of supersampling in xNormal, which leads to artifacts on baked maps. Max has no issue due to samplers like 2.5 Star or Hammersley. Santiago from xNormal did tell me he’s going to add supersampling in the next release!

In conclusin: big ups for Santiago, he’s areally great guy and it’s not the first time he’s been really helpfull and responsive to me. On the other side, boo on Autodesk for not fixing this issue for … years!

Camouflage Textures

Laurens — Mon, 10 Aug 2009 21:11:58 +0000

I was talking to 3DRobbo a few days ago, about his Mazda RX7 model that he wants to texture with camouflage. The issue of painting across seams came up and I remembered something from my Internship. The technical artists used a 3DS Max procedural material, a plugin from Blur Studios, that required no UV mapping. He then rendered that material to texture via Max’s Render To Texture interface. A very smart way of handling things, saves you the agony of having to paint across seams consistently. Definitely recommended for any artist that wants to texture camouflage.

For the sake of illustrating things, here’s a test from Rob:

The Blur plugins can be found here:

http://splutterfish.com/sf/WebContent/DownloadTools