A discussion about Mudbox and Zbrush-style shading arose on the Softimage mailing list. Their signature look comes from “MatCap” shaders (originally known as lit-spheres.) It’s a popular way to achieve a custom lighting solution from a texture, in realtime, which is particularly useful when modeling – you can get a nice clay or sculpy “look” to geometry in realtime. It’s also useful for creating nonphotorealistic (NPR) looks in realtime, toon shading etc.
As mentioned in an earlier post, the grey-ball shader in mental ray can render litsphere textures, and a user suggested that in the high quality viewport you can get the desired result by plugging the metaSL node “Map_ball” into the environment channel. The problem with this is the result (on my machine, at least) appears in world space. A proper litsphere should be in view space.
But it called my attention to something important – almost all of the metaSL nodes used in Mental Mill are now accessible in the render tree and can be used similarly – meaning for most intents and purposes all softimage users now have Mental Mill. Which is awesome.
But we still needed a solution for matcap functionality in the high quality viewport. So I bit the bullet and wrote a metaSL shader which seems to do the trick. It can be used for both realtime performance in the high quality viewport as well as full renders in mental ray (and any other platform supporting metaSL.)
Update: Daniel Brassard kindly fixed some bugs, the new version is now available below. Thanks Daniel!
Here’s the shader (MetaSL ~2kb): litsphere_v1_1
More examples of the shader: