Join Brian Bradley for an in-depth discussion in this video Creating a translucency effect, part of SketchUp: Rendering with V-Ray 3.
- [Instructor] Now although both the generic and sub-surface scattering materials can be used to create thin object translucency, getting them to work and work well can, in my experience, take a quite a bit of trial and error, and so in this video, we're going to walk through creating a quick and easy fake translucency using nothing more than a couple of generic materials and a V-Ray two-sided material. We already have the two generic materials that will be applied to the front and back of our tablecloth geometry sitting inside the material list.
These are using just straight diffuse colors in this instance but if you were willing to take on the challenge of UV-mapping complex shapes in SketchUp such as this tablecloth, then you could instead use bitmap files if you wanted. Now I have used the names front and back on the materials here as that essentially is how SketchUp and V-Ray will ultimately see things given that they will apply each of these materials according to what they think constitutes the front of the back faces of the geometry. Next we need to create our two-sided material and so from the Add Material list, let's add a two-sided material and call it tablecloth.
As you can see, this material has a very simple control set in that it has two slots named front and back which as you would perhaps suspect is where we will add our front and back materials and so let's go ahead and select our front material for the front slot and the back material for the back slot. We then need to go down to the surface level of our tablecloth geometry and right-click the tablecloth material so that we can apply it to the selection. Now initially, nothing will change in the SketchUp viewport simply because our front and back materials have just grayscale values assigned to the diffuse slot.
Let's change that though by first of all coming to the front material, giving it a nice obvious red color and then let's go to our back material and add a blue color in there. Now you may wonder why I'm using red and blue but these are really just debug colors that I like to use as they make it very obvious to me what is going on in the scene. You can of course assign finished colors here if you want to. If we take a render now, because the translucency color here is set to a light gray value by default, we see that we get a very obvious blending of our two colors, essentially giving the impression that direct light is shining through the cloth and blending the two colors together.
To prove that it is the translucency control that is causing this, let's set the color swatch to black and render again. What we see now are the very distinct colors sitting on either side of this piece of geometry with no blending at all taking place. When it comes to creating the illusion of translucency though, what I typically find is that we generally want a pretty small amount of color to be bleeding through to the back material. If I just set the translucency color to a relatively low grayscale value of around about 60 then, and render again, we can see that our translucency effect has improved quite a bit, in my honest option that is, given that we can now see where the folds in the geometry are occurring, the brilliant thing here being that we now have two separate materials on our tablecloth that can have completely different properties assigned to them.
The downside though is that this is just a material trick. We don't actually get any light at all passing through the material and so lighting underneath the table is not affected. If we wanted to give the impression that the shadows were being somewhat brightened by sunlight passing through the fabric, then we would need to add some extra lights in here to be able to fake that. What we have seen then is that we can use our generic and two-sided materials to create thin object translucency or at the appearance of it, and of course this trick doesn't apply to just fabrics.
We could add this to foliage, to paper, in fact, to any object at all that would let direct light pass through to some degree or another. All we have to do is wrap our generic materials inside a two-sided material, tweak the translucency option, and we should find that we have created a very nice fake effect for ourselves.
- 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