Creating a translucency effect

In this video, we are going to do a little bit of extra work on our tablecloth material. Really we want to take what we have so far and make it behave a little more realistically, a little more organically in respect to the scene's lighting setup. To do this, we are going to make use of a couple of V-Ray materials and a new one, the V-Ray 2-sided material. We do need to switch cameras inside our view, so let's come to the Panels Menu, and I'm just going to choose this CAM_ TableCloth option, and you can see we have a brand-new perspective on our scene.

If we take a render, just to remind ourselves of what we have so far in our material setup. You can see the things are just as we left them. Our pattern is working fine, our colors are looking good in the scene. However, at this moment in time from this particular camera perspective, we are looking essentially directly into the V-Ray sun that is settled in our scene. Now from such a point of view, we would expect to see light passing through our thin fabric object here and yet, as we can clearly see that is not the case.

This is the effect that we are going to use our V-Ray 2-sided material to create. I'm just going to save the render that we have at this moment of time so we can make some comparisons. Of course we need to pull up the Hypershade window for ourselves, so let's just put Render View out of the way for a minute or two. Come up to Rendering Editors>Hypershade. Now in the list of materials that we already have settled in the scene, if I just scroll down, you can see we have this Translucency_Test material. This is a V-Ray 2-sided material and you can see we have a couple of materials set in the front and back of material slots.

These essentially are just two V-Ray materials, standard V-Ray materials, one is set up with a diffuse blue color, one is set up to be a diffuse red. If I just select our tablecloth object in the scene, we can just use our right-click and Assign Material To Selection option, that is now applied. And we can show you the effect that the V-Ray 2-sided material in its current setup will have on our object. So we have our render set, so let's take another one. And what we get is probably what we would expect.

So let's just go and select our material node. Again you can see we have our Front Material showing up on the outside of our cloth, of the front side according to the way the materials have been assigned, and our red material is showing up on the back or the inside. As if yet though, we don't have any kind of a Translucency effect. We're still not seeing light penetrate or we are not getting the impression of light penetrating through this object. That is because of our Translucency Text Swatch, now we could use a map to control our translucency effect, but we are just going to work with our Color Swatch.

This essentially turns the translucency effect on or off with black set which is the default, we have no effect occurring in the scene. But if we just click our Color Swatch, and if I just come down and if I set a color value of around about 0.07, so we are just working with the grayscale value here, and if we take a render effect, let's say what we have, and if we just make a comparison, you can see that something has definitely happened.

We are not really getting what we would call a decent looking translucency effect at this point. That's because there is one option that we have failed to take into account. That is this Force single- sided sub-materials option. If we just come and look at our V-Ray materials, you can see that if we scroll down to the Options section, you can see that by default V-Ray material is setup to be Double Sided, in other words, this blue color is trying to apply itself to both sides of our piece of geometry.

And of course the same is true of our red material as well, so there is a little bit of a conflict going on here. Really what we need to do is at a top level of our V-Ray 2-sided material, we need to enable this Force single-sided sub-materials option. Of course we could turn off the Double-Sided option in each of the V-Ray materials if we wanted to, but if we had a complex setup, that might take a little bit of time. This option is a nice easy one to work with, so again, let's save what we have and see how that is affecting our material.

And what we get now is a much more believable translucency effect. You can see where the folds of the cloth come around. We are getting shadow information showing through, we can see dark areas, so something that's looks much more akin to a genuine translucency effect. We do need to be aware though that this essentially is a material trick. This will not affect any of our scene's lighting, so the shadows underneath our tablecloth will not be affected by this change in our materials. If we wanted to brighten those up a little bit, we would have to play with our lighting or global illumination setup.

Well we are not finished here yet, because we do want to of course reapply our tablecloth material. What we are going to do is let's just pull up our Hypershade window, and if we just find our original tablecloth material, the V-Ray material, and I'm just going to middle-mouse click on that, and we are just going to drag that and apply it to the front slot in our V-Ray 2-sided material, and again, if we save what we have and take a render. Then you can see with that change we get a very nice effect indeed. We still have our bright checkered pattern, so if we were to switch back to our table-top camera view, the material would look just as it did before.

But let me come down to this point of view, we get a very, very nice translucency effect indeed. So with just a couple of V-Ray materials and some help from the V-Ray 2-sided material, we've created, as we say, a very nice translucency effect for ourselves. Of course, we could have used more complex materials such as V-Ray's SSS options, but if we need to create thin surface organic effects such as paper, foliage, or indeed as we have here, fabric, I would highly recommend trying out this particular approach first.