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When you use Spot lamps you have an additional type of shadow that you can use, and that's called the buffer shadow. Now these are shadows that are created using a bitmap, rather than ray tracing, and they can render much more quickly. So if you're using Spot lamps, it's a good idea to take a look at buffer shadows to see if they'll work for you. Now I have a simple scene here with a Spot lamp shining on a cup, and this is the scene we used in the last lesson. And let's go ahead and select the lamp and change the shadow from Ray Shadow to Buffer Shadow.
Now we have a number of options with Buffer Shadow. The first one is the color of the shadow, which is pretty much the same as you have for the Ray Shadow. And then down here we have controls for this specific type of shadow. And we have a couple of different buffer types, as well as controls for those buffer types. Now we're going to take a look first at Classic-H, which is probably the one you're going to use most. It's actually an update of the Classical one. It actually works a little bit better.
So under this we have, first of all, Filter Type, and this is basically how does it blur the shadow? We're just going to leave this on Box. And then down here we have a Softness control, a Size control, in other words, the size the bitmap uses calculate the shadow, a Bias control. Now this controls how the shadow aligns with the object. Remember, this is a bitmap that is overlaid on the image, so this controls how that works. And then the number of Samples. Now this is the number of samples to create a soft shadow. So let's go ahead and just do a quick render here to see what the default give us. And as you can see, it's a very workable shadow. So let's take a look at some of these controls.
Now the first one is called Soft, and let's go ahead and just dial that down to 0 and render. And as predicted, we get a very hard-edged shadow, because softness is 0, and not soft is hard. So if we want, we can dial up the number of samples and that can make the shadow even crisper. Now this size here is just the size of that bitmap that it calculates. If you get too big, you're going to have more bitmap than you have image, so large numbers really kind of give you a diminishing return; after a certain size, they don't really have much effect. But you can see when I turn it up to 2048, I get a much crisper shadow.
That's because a 512, I'm actually under-sampling in relation to the image, so you can see how I'm getting a much crisper shadow here. Now I'm going to turn that back down to 512, and let's go ahead and turn softness all the way up. I'm going to turn it up to a very high number. Originally, it was at 3, but I'm going to bring it up to 32. And this will actually shows you how it calculates this shadow. So with a very high value for Soft, it shows you how it calculates a sample.
You can see we have a bunch of different samples of this shadow from different angles. It moves the light around to give you different shadows, and then it blends those together. But the larger this soft value, the further it moves the light, and so you get this multi-shadow affect if you have not enough samples, and that brings us down to this. This is actually the number of samples we're using. How many times do we move that light? So with 3, with a Soft value of 32, you notice you're not going to get a really good-looking shadow, but we can certainly bring that up. So let's bring that up to, say, 10 and then do a render.
Now with more samples, that means it moves the light more times and it has more sub-shadows to blend together to make this soft shadow. And notice how the shadow looks soft and it looks really nice, and more importantly, it renders a lot faster than a ray-trace shadow. Now I'm going to bring my Samples back down to 3 here, and I'm going to bring my Soft value back down to 4, and then I'm going to do a quick render here. Now we're using the Classical-H buffer type.
Now one of the reasons we use the Classical-H buffer type is because it's a new algorithm that Blender instituted back in 2.4 or so, and what it does is it prevents objects from self-shadowing and actually corrects some errors in the original algorithm. So with these values, if I go into a Classical buffer type, you'll actually see some of the errors that we can get. So because of the specific values I have, we actually have a little bit of an error here in that we have a white spot in our shadow, and that's what can happen when you use this Classical buffer type.
So I tend to always keep it on Classical-H. Now if you want, we do have some additional buffer types. We have what's called a Deep buffer type. Now this has all the same controls as Classical and Classical-H, but it has a compression value for the shadow, and what that does is it gives you more bit depth in the shadow area so that way you can get more image in that shadow. This is really better if you render at higher bit depths.
Now the last one is called a Regular Shadows, and that's really just a very simple, basic shadow and it basically just renders a simple shadow like this. And we only have one control which is for Bias, and so a higher biased value, say such as 3, will give you a slightly different result. In other words, the bias basically just moves the shadow. Notice how the shadow moved a little bit forward here. So I tend to keep my shadows on Classical-H. Classic-H is probably the best general-purpose algorithm to use. But remember, buffer shadows are based on a bitmap, which means they render faster, particularly for soft shadows.
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