Join Brian Bradley for an in-depth discussion in this video Understanding color on the SSS material, part of SketchUp: Rendering with V-Ray 3.
- [Instructor] Having already seen how we can create a quick and dirty fake translucency effect in V-Ray for SketchUp, let's take a look now at the genuine sub-surface scattering material that we do also have available. As is oftentimes the case, the best way for us to understand just what this material is and what it can do, we need to take a look at it in action, and so to do that, let's first of all add a new sub-surface scattering material to our material list, dig down to the surface level of our shader ball pieces, and then right-click and apply our material to them.
Finally, let's go ahead and take a render of what we have. As soon as the render is complete, we get a very unique look and feel regarding the type of surface that we are now looking at. With light clearly bleeding through the thinner areas of the geometry, we instantly think of this as representing a much softer, perhaps more pliable type of substance. As we look at the control set for material in the asset editor and open up the rollouts, we do see that we are given a lot of control over how our sub-surface scattering effect will eventually turn out.
Now obviously, we don't have time here to cover every single option that we see but what we will do is look briefly at some of the major controls for the material and try to demystify a little bit how they work, focusing mostly on the color elements which is where users oftentimes find themselves getting frustrated. Having said that though, the very first thing that we will do here is come to the single scattering options and switch the single scatter type from simple over to ray trace solid, and then we can render again.
Now obviously, using the simple rather than ray-traced option gives us a much faster render, but as you can see in a comparison, a much less accurate and less obvious sub-surface effect, which is why this is the first switch that I will oftentimes make when using this material. If we are creating transparent materials in the scene of course, we may want to use the ray-traced refractive option instead, as this will also produce transparent shadows which can oftentimes be desirable with that type of material.
Coming back to the diffuse and sub-surface scattering controls then, let's for the remainder of this video, focus on getting a clear understanding of how the diffuse, sub-surface, and overall colors work together. With the diffuse and sub-surface options essentially being the inner and outer colors of the objects with diffuse affecting the surface color and sub-surface affecting the interior volume. To demonstrate how this works, let's set our diffuse color to pure yellow and our sub-surface color to pure cyan.
Now because our diffuse contribution by default is set at zero, all we are seeing in the preview at this moment in time is the sub-surface color. If we set diffuse contribution to one though, obviously now it is the diffuse color, and of course, with the diffuse contribution of 0.5, we get a 50% blend of both. What the overall color is doing here is acting now as a filter for both of the color options that we have just changed, controlling how much of each is seen in the final material.
It does this by using its own RGB values to determine or filter what percentage of the RGB channels from the diffuse and sub-surface colors should be visible. So pure white here is letting 100% of both sets of color channels come through, which is why we can get pure yellow, pure cyan, and a 50% mix of the two. If we were to set the overall color to a medium gray though, we can no longer get those pure colors as we are only letting 50% of their RGB values come through to the final material.
Now this filtering process means that it is probably best to stick to using just grayscale values in the overall color swatch as things can get really confusing once we start to introduce actual color values to it. To demonstrate, let's switch our diffuse and sub-surface colors over to pure red and pure blue and then set our diffuse amount to 0.5. What we get from that is exactly what we would expect given our explanation so far.
But watch what happens if we set our overall color to a pure green. All we get now is a pure black return, which again, given the explanations that we have looked at, does make perfect sense, seeing as now the pure red nor pure blue have any green values in them at all and so we get a completely black return. The big problem for us here is that predicting how mixed color values in the overall color swatch will affect our material becomes a minefield that is fraught with potential frustration, hence the recommendation to stick to using just grayscale values in the overall color swatch.
- Gamma handling in V-Ray 3 for SketchUp
- Working with interactive rendering
- V-Ray light types
- Working with irradiance mapping
- Rendering animations
- Working with the V-Ray camera
- Using the Materials UI
- V-Ray FX tools
- Stereoscopic 3D rendering
- Using V-Ray objects