Learn how to control advanced transparency effects.
- [Instructor] For transparent or refractive materials, using the Arnold Standard Surface, we will adjust the transmissive properties. But the first order of business is to disable the opaque flag on any transparent objects. In our scene I have a vase or vase and also some water within it. That water is a little bit difficult to select in the viewport using the mouse. So let's open the Select From Scene dialog with the appropriate hot key which is H.
In the Select From Scene dialog, select vase edited, hold down Ctrl and select vaseWater, click OK. Both of those objects are now selected. Let's add a modifier. Go into the Modify panel. From the modifier list, choose Arnold Properties. Open the general properties. At the bottom of the general parameters rollout is a section also labeled General. Turn the General section on and you want to disable all of the options in the General section.
Disable opaque so that objects can participate in transmission rays and be rendered transparent. Also disable Double Sided so that the object surfaces are single sided and only the normals facing the camera will render. If Double Sided is on then each surface counts twice toward the number of transmission rays required for transparency. You would need to double the number of rays which would slow down the rendering. But beside it is only useful for infinitely thin surfaces such as plane primitives so that both sides will render regardless of the normal direction.
Now we'll actually be able to see the effects of transmissive properties in the Arnold Standard Surface. However, we may run into an issue with dark areas in the rendering due to low ray depth. Let's look into that. Go to the Render Setup dialog. I've currently got the target as ActiveShade Mode. Go into the Arnold Renderer tab and we have the ray depth here. The specular ray depth is only one bounce and that's not sufficient for highly reflective surfaces near one another, such as water and glass.
Increase the specular ray depth up to three. And that's the minimum number to avoid dark areas on, for example, the surface of the water. Also, for refractions, we need to increase the transmission depth. And the default value of two is nowhere near enough. Think of it this way. You need to be able to render the object that's behind all of the refractive surfaces. And each surface, whether it's an interior or exterior polygon, will count towards the ray depth.
Here I've got the vase, which has got a front and back, and that's four surfaces total. And then I've also got the water. That's going to be two surfaces at a time, front and back. And also we need one more ray for the background itself. And you add four plus two plus one, you get seven. We'll set the transmission ray depth to seven. And the ray limit total down here under depth limits is set to 10.
We've got a total here of 12. Let's just play it safe and set the ray limit to 20. And now we shouldn't see any dark areas in the reflections or refractions. We can do an active shade rendering now. I'll close the Render Setup dialog. Click in the perspective view to make sure it has focus, and click the active shade button. Now let's open up the material editor. And we want to get at our vase material.
Use the middle mouse button to pan around. Here it is. Vase Arnold Standard. Double click on that. And we need to change a bunch of parameters because it's currently set to a gold material. The base color, we'll set to white. The base scale we'll actually set to zero. Enable Caustics should be disabled. The specular scale of one is good as is the specular reflection color of white. The specular roughness we'll set to 0.05.
In the advanced section, metalness should be zero. The index of refraction is set to 1.52 by default and that's fine for normal glass. We previously set the anisotropy to 0.6. Let's bring that down to zero. And finally in Transmission, General, we can increase that weight or scale amount. And now we're getting our transparency. We want to absorb a little bit of light. Let's set the transmission scale to 0.95 for glass.
We can get in closer, take a better look. In the perspective view, use the wheel to zoom forward. Middle mouse button to pan around. If we select the vase object and then use Alt and middle mouse we can tumble around. Just for safety's sake, because we're working with X-Res, I'd like to back up this material. I'll just put it into a sample slot at the bottom of the material map browser. Take the output of that new Water Arnold Standard and drag it over to a sample slot and choose Instance.
We want to select the water in the scene. And for that we can use the Select From Scene dialog which is the hotkey H. But we should give focus to the viewport first. So click in any viewport and press the H key. And from the Select From Scene dialog, select vaseWater. Click OK and now the water is selected. And the Water Arnold Standard node is selected in the slate material editor. And we can click assign material to selection.
And immediately in the active shade we can see that the duplicate material has been applied to the water and we can see through it now. Let's go into the parameters for that new water material. Just change the index of refraction to 1.33 for water. And also make it a little bit more transparent. Set the Transmission, General scale to 0.98. And those are physically accurate values for glass and water. If we scroll down a little bit in the transmission section we come to advanced.
We have dispersion abbe number. And this is the chromatic aberration. Higher values will constrain the rainbow effect of the aberration to a smaller area on the screen. For a very dramatic effect we can set the abbe number to a low value to simulate a dense material such as diamond. Set that just temporarily to a value of 10. During the preview render we see some colored artifacts. And when the render completes, hopefully we'll see some kind of rainbow effect.
And that will be a subtle effect and will depend upon your angle of view and a lot of other factors. We can tumble around in the perspective view using Alt and middle mouse. And take a look at this from a different angle. Especially one where we're getting a strong highlight. With a dispersion value of 10 we're getting a really unrealistic result, as if this were a solid diamond. Let's set it to something more realistic for water. Say a value of 50.
Likewise for the base material. We can set its abbe number. Double click on that vase material and scroll down. Dispersion, set it to a value of 30 for dense glass. Also in the advanced section is extra roughness will give us a frosted glass effect. Set the extra roughness to a value of 0.2. And finally if this is frosted glass, we should also have a little bit more roughness to the specular reflections themselves.
I'll set that to a value of 0.1. That's how to set the transmission parameters of an Arnold Standard Surface for glass and water.
- Arnold rendering concepts
- Arnold lights such as quad, spot, and distant
- Modifying Arnold object properties
- Filtering light with the gobo filter modifier
- Image-based lighting with Skydome
- Daylight simulation with Physical Sky
- Arnold Standard Surface material parameters
- Diffuse, opacity, and bump mapping
- Rendering refractions with Transmission
- Building an Arnold shading network
- Test rendering with utility map
- Mesh subdivision and displacement at render time
- Atmospheric perspective with scene environment fog
- Rendering a spherical environment with VR Camera