Skill Level Intermediate
- [Instructor] Global illumination, or bounce light, is relatively fast in the Arnold Renderer because it's an optimized renderer. However, in many cases, your render times are still too long, and Arnold is not fast enough. Animation is one area in particular that benefits from shorter render times. This week I'll show you how to set up Arnold for a very fast render that looks plausible but does not use global illumination and therefore will render in a fraction of the time.
This is just a technique from the olden days, sometimes known as fakeocity. We're applying an overall ambient light to the entire scene in order to give the impression of bounce light. Let's check out the render setup. Go in there. And I've got my scene set up for ActiveShade mode rendering. In the system tab, I have Legacy 3ds Max Map Support enabled, and I'm rendering on all but two of my current processors threads, or cores.
In the Arnold Renderer tab, I have default samples and ray depth. Let's take a look at this. Click on the render button to execute ActiveShade. And we get an image, but it looks pretty grainy, and that's because of the method I've employed here to light the scene. There are no actual light objects active in the scene right now. The illumination is coming from the emissive material applied onto these ceiling panels. Let's take a look at that. If we go into the material editor, you can use the keyboard shortcut, which is m.
Here's the emission node, which is an AI standard surface material. Double-click on its name to load its parameters. And near the bottom you'll see emission, it's got a value of three. If I set that to zero, then I turn off all light in the scene. OK, I do want those ceiling panels to be self-illuminated, but I'm going to actually disable GI, so they won't actually emit any light. This value only needs to be enough in order to make those panels give a pure white in the rendering.
So I'll set that to a default value of one. Close the material editor, and also close the ActiveShade because I want to make changes to the render settings. We've got a default number of bounces of one. Let's bring that down to zero. We're now going to get no diffused bounces. Likewise, with the specular ray depth, bring that down to zero. No specular bounces. And refractions I'm also going to set to zero because they don't apply in this case. But you might need to play around with that in your own scenes if you have transparent objects.
Now, I've got a scene with no global illumination. So let's see what that looks like when we click render. All we get are the self-illuminated ceiling panels. But I have some lights already in this scene ready for us to enable. Let's go into the layer explorer, and it shows up at the bottom of the command panel by default. I want to tear that off so I can get at that. I've got my UI locked, so I'll unlock that with customize, lock UI. Drag that layer explorer out, expand its size, and then turn the lock UI layout back on again.
So we can get a look at what we've got in here. We've got a layer called lights ceiling. Make that layer visible. And now we can select those lights in any view port such as this front view here. Go to the modify panel and turn that light on with its light properties. And I've got 10 lights, they're all instanced. So when I flip the switch here, they all turn on. So that's a much faster render, and it's much clearer and much less grainy than what we had, but we have no global illumination now.
I should mention, by the way, that these lights are actually behind the ceiling panel geometry, and that geometry has an Arnold properties modifier placed on it so that it won't cast shadows. Now we're ready to apply our ambient light. I'll close the ActiveShade and create an Arnold light in the front view port here. Go to the create panel, lights, from the pull-down list, choose Arnold, click Arnold light, and click and drag from top to bottom in the front view port, release the mouse, right click to exit creation, and then go over to its modify panel, disable the targeted option, and let's check out its rotation.
Just go into rotate transform and right-click. We just want all of these values to be zero. Zero, tab, zero, tab, zero. And now that's correctly aligned so it can be made into a skydome. Over here in its parameters, change its type to skydome. Finally, let's rename it, let's call it ambient light. Let's see what that looks like. We'll execute another ActiveShade rendering.
And it's certainly working, it's just way too bright. In that Arnold light parameters, down in color intensity, we have intensity and exposure. Bring the exposure down to negative three. And now that's a pretty balanced amount of light coming in through the window. The exposure value needs to be so low because I have photometric values for the ceiling lights. And although this is not strictly photometrically accurate, it looks good in the final rendering.
That is to say that the amount of light coming from this skydome is less than it would be in the real world. And we're kind of playing a trick here with nature. But we're trying to achieve a certain look, and we're doing quite well in that regard because we got a convincing light coming from the outside of these windows. However, if we look a little bit deeper here, it's not quite right just yet. Let's go over to one of our ceiling lights and just temporarily disable it in its light properties.
Now we can see that the skydome is only coming from outside these windows. And because of that, we're not getting any illumination in the back here. I actually want this skydome to be an ambient light. I don't want it to have any directionality. And to accomplish that all I need to do is just disable its shadows. Reselect the ambient light, the Arnold skydome, and in its parameters, under shadow, disable cast shadows.
Now we have an even wash over all of the geometry. Of course, it's too intense. Let's bring the exposure down to its minimum value of negative five. And it's still a bit too much for bounce light. So let's bring the intensity down to 0.3. And that's our ambient illumination. If we wanted to, we could go deeper into this. In the contribution area, we could decide, for example, that we didn't want specular highlights from the ambient light. But I'll leave all those values at their defaults of one.
Let's re-enable our ceiling light. Select it and turn its light properties on. And we're getting closer. We have good coverage back here in the shadows, but we're not getting any of the strong directional illumination that we saw when the skydome had shadows. Well, I thought of that too. I've actually got another set of lights outside these windows that serve just that purpose. And in the layer explorer, we can see I've got a hidden layer, lights exterior.
Un-hide that, and we can select one of these lights and turn its properties on. And now that's providing the direct illumination from the window. So we have the artificial lighting from these photometric lights in the ceiling. We have a fake lighting from the environment, which is coming from these other photometric lights that are scaled quite large, actually. We can take a look at that, in the perspective, you dolly back. I've got those exterior lights very large and very far away to provide an even illumination through those windows.
OK, we're nearly finished. We've just got a couple other details. One is the color of these lights. The ones that I've previously set up have varying color temperatures. These ones from outside are at 6,500 kelvin. The interior artificial lights are at 4,800 kelvin. And let's take a look at my environment dialog. Go to rendering, exposure control or environment. I've got the camera set up to be 5,000, which is somewhere between those two values for a balanced look.
So let's set the Arnold skydome to be the same as the camera here. I'll select that skydome or ambient light. And we want to set its kelvin value in color and intensity. We'll set that to 5,000 to match the camera. A bit of a subtle effect, but we're essentially splitting the difference between the color of the exterior light and the interior light to give the color of the overall ambient illumination. All we need now is a backdrop. I'll close the ActiveShade and close the layer explorer as well.
We've got, in our environment dialog, the environment map. Click on that none button, and from the material map browser window, we want to scroll down into maps. OSL. Here's OSL, our Open Shading Language. We've got a handy one here, black body. Select that and click OK. It's assigned. Let's take a look at it in the material editor. Open the material editor and drag the map over into the view and choose instance.
Double-click it to load its parameters and rename it, we'll call it backdrop. This gives us two colors in a gradient. You can double-click this and make it larger. We just want these both to be 6,500 degrees. With a value of 6,500 kelvin, the background will be slightly bluer than the camera, which is at 5,000. OK, let's take a look at that, and we'll do another rendering. And we've got light coming through the window, which we didn't have before.
So there's one more thing we want to do. We get a skydome for free whether we want it or not when we add something to the environment dialog here. So I'll close ActiveShade. Go back into the render setup, and in the Arnold Renderer tab, scroll down near the bottom. You're looking for environment background and atmosphere. By default, this is going to convert your environment to an Arnold skydome. But we already have an Arnold skydome, and we already have light coming through the window.
So we don't need this here, and we actually don't want it, because I want to separate the color of the background from everything else. Set the mode here to advanced, and then disable enable environment lighting with skydome light. Once we've done that and our background is set to the scene environment, then this black body color will show through as a background but won't add any light to the scene. We'll do our ActiveShade once again. And now we've got no extra light coming through the window.
And so we can see exactly what's going on here. We've got an intensity amount. Let's bring that down to .1, and now we've got a blue color corresponding to 6,500 degrees kelvin. We want this intensity to be just enough to blast out that window. If I set it to .2, it's at its maximum brightness. .1, it's not bright enough. Let's do .15, and that's just bright enough to make those pixels perfectly white.
And the reason this is important is because if the intensity value is too great out there or on these lights or wherever, that intensity will result in jagged pixels in your rendering. We can kind of see that here with my emission. It's looking a little bit jagged there. So I can go into that emission once again and reduce the emission amount. Let's say .2, and that way the light's not blasting out too much, and the anti-aliasing engine is able to do a better job.
OK, this is pretty good for a draft-quality render. If I wanted to do a final-quality render, I would just go back into the Arnold Renderer and increase the camera anti-aliasing up to a value of five. Let's do one final ActiveShade render with the higher camera anti-aliasing settings. And it will take a little bit longer, but it's still much, much faster than global illumination. That's how to set up a scene in Arnold to give the impression of ambient light, allowing us to disable global illumination and speed up our render times.