SSS Experiments

Sorry I've not posted in awhile, hopefully that will change with the Everyday Art project.  In case you hadn't seen it the idea is to create a piece of art from start to finish every day.  Doesn't have to be good it just has to be started and finished.  Even though the artist Beeple (Mike Winklemann) titles his site Beeple-Crap, his work is anything but.  That probably has alot to do with the fact that he's been doing it for over 10 years. 3293 consecutive days of publishing new work every day.  As my Art History professor at A&M, Joe Hutchison would say "But I digress . . ."

The last week and a half I've been messing around with Sub Surface Scattering.  Fascinating subject, hugely complicated material with lots of settings that I have NO IDEA what they do.  The documentation from Chaos is great at giving the techincal definition of what each setting is but LOUSY at telling me what it DOES. Or why, or how, or simply what to expect with certain values. So here's me at 10 pm at night mashing buttons and changing settings like a great dane in front of a computer hoping to get something in the next 2 hours that doesn't suck completely because I have to post it even if it does.  Fortunately my first two attempts came out pretty well.  I'm going with beginners luck.

     











The Fast SSS shader has 12 presets. The majority of the renders I've done use either the Milk (whole) or Milk (skimmed) presets with a few changes to scatter radius and color. I started to be able to produce closer to what I wanted without a huge amount of trial and error, but there was still some guesswork involved.

 












So I decided to sit down and make some notes on the various settings I'd played with.  I put together a video of the results and it can be found on Vimeo. It's by no means a definitive tutorial on SSS or Vray, but if you're like I was a week ago with no idea of what settings do what, this may help get you started.

Check Out the Video Here

Material Update

My primary client is a kitchen equipment manufacturer.  98% of what they fabricate (and that I render) is made of stainless steel.  So I am constantly tweaking my stainless steel shader.  After a number of years working in Mental Ray, I switched all their renders to Vray.

I developed a shader based off everything I had learned from Mental Ray, and combined it with info from Grant Warwick's shader creation techniques.  After having had it in production for a few months, and really getting to see it in various scales and scenes, I had alot of notes on what I wanted to update, and I recently took several days off after completing a large project to do just that.

The shader is a Vray Blend material that uses 3 layers of materials.  The layers are then blended with a falloff map with a custom curve drawn to show a different shader based on viewing angle.  The idea being that a materials reflectance increases with the viewing angle.  Here's an example to illustrate what the material is doing.

The red areas are those facing more or less directly to the camera.  The blue areas are those almost 90 degrees to the camera.  The green are the values in between.  When this is applied to the stainless steel shader, the red areas show the least reflective of the material and the blue show the most reflective.

The next issue is that nothing is perfectly flat.  I've been using a noise map in the bump slot of the shader to create the "wobble" found in sheet metal.  This is set to a world space so no matter what mapping coords you place, the wobble will be random and consistent.  It also allows smaller objects to not have very much distortion and large ones to have more.

The 3 renders are each of a different scale (left to right is largest to smallest), but use the same mapping coords.  The brushed texture is very small and fine on the large model and larger and more visible on the small model.  The edges of all 3 are chamfered at 1/16"  The render scene is a modified version of Grant's.  Download the shader here.