Emission volumes for quick rendering

- [Instructor] Volumes like smoke and fire are awesome in Blender, but their biggest drawback is speed and memory use. To get those cool-looking effects in Blender, you take a serious hit on your render times. What are you to do? Well, in this week's Blender's Tips, Tricks, and Techniques, I'm going to show you a way to speed up your volume rendering. First, let's delete this cube and lamp. Let's switch to cycles. I'm going to shift a, add a monkey, and shift a, add a sun lamp.

Let's put that sun right about here. I'm going to click on this monkey, type spacebar quick smoke, and without doing anything else, I can just play this, and see some pretty cool smoke. Now if I want to hide Suzanne, I can turn off render ability. And to speed up our rendering just really quick, I'm going to go to sampling, and change my render samples to 32. So now let's go up to render image and see what we get.

Hey, great! Now we have a monkey, but you can see that it took us about 19 seconds to render, and it peaked memory of about 1.75 megabytes. So let's see if we can do better. Switch to 3D view. Let's pull this open. Let's go to Node Editor, hit end to get some more real estate, and let's select this attribute right here on the left that says density, and hit shift e, bring him down.

Let's add a few nodes. Shift a, search. We're going to add a color ramp, and connect this factor here. We're going to shift a, add a math node, put that right here, and go color to value. Switch add to multiply. Shift a, search. Let's add a emission.

Leave that right here. Value to color. And then, let's bring down the material output, and drag my emission right over the volume. Now don't worry, it'll disconnect the previous one, but it'll still be there if you want to look at it. Now you should have a node set up that looks a lot like this. Okay, so if I go ahead and render, we'll see the difference. But first, let's go to UV/Image Editor, middle mouse drag this bottom area, and look for slot one.

Click on it, and pick slot two. I'll show you what that does in a second. Now go up to render image, and hey, look at that! We rendered a smoky white monkey. Now if you compare slot one to slot two, you can see a few differences, notably in the color, but you can also see how much quicker we rendered, almost half the time, and little bit less memory. Now the reason why it's smoky and not as, well, volumetric, is simply because we're using an emission shader, and so we're going around all of that complex light calculating, with light rays bouncing among all of the volume.

We're just keeping it nice and flat. However, because it's an emission, it is a bit bright, so I recommend you play with this multiply value. I'm just going to pick 0.75 really quick. And let's go to slot three, and let's render that. Perfect! Now you have a monkey that has a bit more of a darker hue, and you can always compare, just drag into a little area here, and go to slot one and slot three, and you can kind of see the difference between the two.

Now a quick head's up. This trick isn't going to give you a beautiful volume, smoke and fire, and it's also not going to react to light, because it's emission shader. But, if you did need a bit of smoke, say in the background, fog up in the foreground, something that you didn't really need to pay attention to all of that nice, volume-looking smoke, this could help out quite a bit. It's really fast, and really light on rendering, and you don't need as many samples to really get a nice, clean image. I hope this helps out your smoke and fire workflow, and until next time, this is David, with Blender's Tips, Tricks, and Techniques.