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Reflections are a vital part of many materials. But how much reflection we need varies widely, depending on the material we're using. I'm going to add a subtle reflection to my metals outside, my door handles and railing frames. The big deal with reflections is that they're computationally intensive. That our real time, raytraced reflection on the floor for example, would bring many game engines to their knees. And doing this on a mobile device is out of the question. They simply don't have the power. So, we'll use some creative fakery in here.
Pre-calculated images that move around and change dynamically. I'll scroll back in my scene and go select one of those railing elements. I'll pick a corner one here and press F to focus in on it. This object is three materials. Dark wood, a metal screen, and a brushed bronze. I'm going to add a subtle reflection in the brushed bronze. First, I'll scroll down and change the shader over from a specular shader. I'll drop down to my shaders and I'll choose under, Reflective, Specular. We can see in the reflections we have a lot of our standard material types.
Bump, diffuse and specular and so on, all the way up through parallax. So we can even add a reflection into our shiny bumpy nubbly surfaces. I'll choose a specular because this is a smooth metal. When you choose a reflective shader, Unity inserts a reflection color and a reflection cube map slot. A cube map, as the name suggests, has six images, one for each side of the cube, so that as we move around it appears to move with us and change dynamically. Here's how I'll put this in. I'll go into the materials folder and my assets folder.
Right click and choose create. And cube map. I'll name this cube map Reflection Sky. And then I'll get images of my sky in there. Now that I've named it. I'm going to bring in the same sky images I used earlier. You may end up wanting to either paint cubes, draw cubes, photo manipulate some cubes, or render cubes in another application like Maya. For now though because these pieces are so small I'm going to use pieces of my sky and tint them using the reflection color. So I get the idea of stuff happening that sort of matches in the scene.
First, I'll get those images in. Clicking on the select button for the right image and going into the sky. I'll scroll down and in the assets folder here's my sunny sky. I'll limit this down by typing in S-U-N and there's my sunny sky. And I'll scroll this out so I can see their full names. Here's sunny 3 right. And then I'll pick, moving this over, the top, and again here's SU and sunny 3 up. Here's the front, filter down, and sunny 3 front.
Left, bottom and back in the same way. This filter is a great tool because it lets me get in and really pick things quickly. Now that I've picked all of my images, I can see in the preview, a sphere. And dragging that sphere around shows that cube apparently moving. In reality, we're just looking at different images that are made to blend together. I've got, in the cube map, a face size, and the choice of MIP-maps in here I’ll check Mipmaps, so that as I get farther away, it down res's. And, I can limit down the face size, if needed. I’ll leave it right now at 64, and see how this looks.
This will also let us reduce that, and blur it down a little bit, which can be handy. Because again in a reflection, we need stuff, not necessarily something clear. I'll go back and select this object, and scroll down to that brushed bronze. Now in the reflection cube map slot, I'll click Select, and there's my reflection sky. Once that's in, my bronze is rather blue looking. I'll use that reflection color to bias it down, and reduce the amount of reflection a bit. In the reflection color, I'll click on the eyedropper, and grab that main color.
And the reflection changes over to be a bronze color reflection. I'll bring this up just a little bit. Bringing up the value. And just the saturation a touch. I'll see if this works. And then see if I need to adjust more. We get in here is a little something going on. Its not much but its just enough in there to get the idea of something happening. We can just see some movement in that surface and especially when we pan up like this to look at the sky. It really has that feel of bronze in there.
In this case perhaps a little too polished. I'm going to pull down the shininess on my bronze and I'll also darken that specular color. One thing to note. You may end up darkening your main color as well, when you're putting in a reflection. It's okay for metals, for that main color to be almost black. So that the material really reads as that dark metal with some of the color contribution coming from the reflection. Now it's got a good reflection to it. I've backed off the shine a little bit. And it really reads as that bronze color for those railings. It's got a subtlety and really what I'm after here is that there's stuff happening in the reflection.
It's not necessarily that they're stunningly reflective, as much as, changing as I move around. I'll put the same image into the window frames as well so that they've got a little bit of sky reflection from the cube. I'll pick any one of the window frame objects and go look at the material. Here's a window frame joining bar and it's got an anodized bronze on it. I focus on and we can see it's that material that's across all of these Mondrean-esque window frames. I'll do the same thing changing from a diffuse over to a reflective specular.
They go white and that's okay. First I'll grab that specular color from the main color and then darken down the main color. Now I'll get the cube map in. Clicking select in the reflection cube map and choosing my reflection sky. Finally I'll take that reflection color, borrow that specular color so it darkens out. And maybe even go a little bit darker. This material is usually a very dark one so we really want that reflection to mute down. I'll saturate it and I'm going to dark my main color almost to black here. And now here's the test.
As I move around, there's definitely something happening in there. But it's so mellow that it just barely shows when I look at the biggest piece. But it definitely feels more like a metal. I'll give it a quick play test to see how it behaves. As I move around and go look at this window frame, it has a rich bronze-y look. And it's definitely kind of a oil rubbed or brushed surface, or something similar. And I can see where the glass goes in. And there's a little something moving that just gives it the idea of being a metal.
The same goes for the railings. I can see as I walk right through them, movement in their metal. I should probably put the same reflection cube onto that metal screen. I'll jump out onto the water and take a look. And again, we can see it really behaving like a brushed metal or A very subtly, soft, shiny metal. That there's a little difference in that reflection. And it's a great way to bring things to life. You may end up wanting to make a custom cube map as I said. Or simply borrowing one of your existing ones and attempting it. We want to save our reflections to things that really need them.
We'll put a reflection in the water for example. Or maybe use a really good reflection on the floor. Or even a custom made cube map. To really make it look like that wood floor is glossy, but for things that need a little bit of reflection on the little surface a small cube mat that gets the idea of stuff moving is a great way to go.
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