Setting a translucent weight of 1.0 makes no sense most of the time right?

Flortale

If I set translucuent weight to 1.0, then the base color texture is no longer shown.  Try it for yourself on a surface. Set the base color to yellow, then set translucent color to red.  Set translucent weight to 1.0 and your surface will be red only.  The whole point of translucency is to show the base color on the top and then the transcluent texture beneath it right? Therefore setting translucent to 1.0 makes no sense unless it's super clear water or something right?

Does it make any sense to use the same color map for both base color and translucent color? I see a lot of surfaces do this, but it doesn't seem to make sense or does it?

For skin, the base color should be the skin texture alone, then for translucency texture it should be veins in addition to red to simulate blood capacity in certain areas yes?

JonnyRay

Setting transluceny to 1.0 (100%) basically tells Iray that all of the light striking the object is passed to the interior of the object. So, you're right, for most (non-transparent) surfaces you would want something significantly smaller than that. As I think you noted in another thread, even 0.1 is enough to see some results without completely losing the base surface map.

As for the color, it depends on what effect you want to have. For instance, if you're creating a blue gem shader, then the light that bounces (Base) and the light that is transmitted (Translucency) should be the same. But if you're trying to show that certain wavelengths of light bounce back, and others are passed through, then different colors would make more sense.

Skin shaders can get crazy complicated. I once read an interview with a professional 3D artist known for his realistic skin who used 5-7 different maps to represent the Epidermis, Dermis, Hypodermis layers as well as blood vessels, sweat glands, etc. To be honest, since many skin textures are based off photographs of actual skin rather than scientifically accurate skin models, trying to add some of those details would look incorrect since they are already accounted for in the photographs used as reference for the base skin texture. That's why many of our skin shaders can get away with just using a single color in the various translucency, and subsurface channels instead of needing texture maps.

 

SpottedKitty

That actually makes a pretty good general point. The Iray shader uses several "master control" parameters that open up groups of related parameters in the Surfaces tab when they're set to non-zero values; Translucency Weight is one, there's also Diffuse Overlay Weight, Glossy Layered Weight, Bump, Normal, Top Layer Weight, etc. Not all of them need to be bumped all the way up to a value of 1; in fact I think some should have quite low values (I'm thinking in particular of some of the glossy ones). Where do we find details of which parameters need to have limited values (and, almost as important, why)? There's a page in the online D|S docs here that gives some details, but it does a pitifully poor job of actually explaining — no matter how many times I read it, I keep losing track of the information I was originally looking for.