Polished Reflection vs Blurry Reflection vs Glossy Reflection

So you may hear a lot of definitions being thrown around like a polished reflection, a blurry reflection, or a glossy reflection. Defining these is actually a little bit difficult since these words can mean different things to different people and in different renderers. But here's the general gist of things.

• A Polished Reflection is an undisturbed reflection, like a perfectly mirrored surface. This is the kind of material I made in my Chrome Material lesson.
• A Blurry Reflection means that tiny random bumps on the surface of the material cause the reflection to be blurry.
  
• Now here's where things get tough. To get Blurry Reflections, most renderers give you a control called "Glossiness". When your Glossiness is a high value, your reflection is mirror like, like a polished reflection. When your Glossiness is a low value, your reflection is blurry. However, many people use the term "Glossy Reflection" as a synonym for "Blurred Reflection". This isn't technically accurate, since a reflection that is very glossy is the same as a polished reflection. But if a renderer says it has the feature called "Glossy Reflections", it means it has the ability to blur your reflections. See how confusing that gets? So just keep in mind, when someone says they used "Glossy Reflections", they could mean that they blurred their reflections, since they used the glossy reflection feature, or they could mean their reflections are quite mirror like, because that's what a reflection that's glossy is. Don't you love it when the same word can mean 2 opposite things :)
  

• Isotropic means the blur is equal in all directions, since the tiny scratches on your surface go in a random direction
• Anisotropic means the blur stretches in a specific direction, because the scratches are all stretched in a specific direction.
  

The basic ingredients are as follows:

• GGX Shader ideally (But Blinn or Phong will do)
• Almost Black Diffuse (The brighter the Diffuse the more it will look like an alloy, ie, a mixture of a metal and another material)
  
• High Specular Reflectivity
• Medium to Low Glossiness (Blurred Reflections)
• Fresnel Reflections, IOR between 6 and 20

• 3dsmax's Brazil Advanced Material in Brazil Rio Renderer
• 3dsmax's Arch & Design Material in mentalray Renderer
• 3dsmax's VrayMtl Material in Vray Renderer
  

3dsmax's Arch & Design Material in mentalray Renderer

Here's an example file to make a scene like the image above using 3dsmax's mentalray Renderer: blurred_raytraced_chrome_mr.zip (Requires 3dsmax 2009 or later, mentalray)

3dsmax's VrayMtl Material in Vray Renderer

Here's an example file to make a scene like the image above using 3dsmax's Vray Renderer: blurred_raytraced_chrome_vray.zip (Requires 3dsmax 2014 or later, Vray 2.4, ColorCorrect)

Again, identical to the polished chrome, except I changed the Refl. glossiness from a value of 1.0 to a value of 0.8. (note, the env is wrapped in a ColorCorrect map to set the gamma correctly, since this scene uses Linear Workflow). I also increased the Subdivs to 32, so that the blur is nice and smooth, without tons of noise.

Blurry Environment Mapped / Polished Environment Mapped and Raytraced Chrome

Anisotropic Brushed Metal Using Small Bumps

Since anisotropic reflections are really just reflections distorted by tiny bumps on a surface, why not just make those fine bumps on our cg surfaces? Well, you can, for example, take a look at the tea kettle that I rendered in Ghost (the predecessor to Brazil)...

So the basic ingredients are as follows:

• GGX Shader ideally (But Blinn or Phong will do)
• Almost Black Diffuse (The brighter the Diffuse the more it will look like an alloy, ie, a mixture of a metal and another material)
  
• High Specular Reflectivity
• High Glossiness
  
• Fresnel Reflections, IOR between 6 and 20
• Stretched Bump map

• 3dsmax's Brazil Advanced Material in Brazil Rio Renderer
• 3dsmax's Arch & Design Material in mentalray Renderer
• 3dsmax's VrayMtl Material in Vray Renderer

Here's an example file to make a scene like the image above using 3dsmax's Brazil Renderer: aniso_with_bumps_brazil.zip (Requires 3dsmax 5 or later, Brazil Rio)

First, make a polished raytrace chrome surface. Then add a very soft, small but elongated bump map, which distorts the reflection primarily along one axis.

While this technique works, it takes a lot of fine tuning to get just the right size and frequency of bumps to produce the type of distortion you want.

3dsmax's Arch & Design Material in mentalray Renderer

Anisotropic Brushed Metal Using Anisotropic Reflection Shader

With an Anisotropic Reflection shader, you can stretch the reflection without the need for a fine bump map (although adding bumps does make the effect look more realistic). Much like an anisotropic highlight, you have control over the amount of anisotropy, and the reflection gets stretched in the direction and by the amount you choose.

So the basic ingredients are as follows:

• GGX Shader ideally (But Blinn or Phong will do)
• Almost Black Diffuse (The brighter the Diffuse the more it will look like an alloy, ie, a mixture of a metal and another material)
  
• High Specular Reflectivity
• Medium to Low Glossiness (Blurred Reflections)
• Fresnel Reflections, IOR between 6 and 20
• Anisotropy turned on

• 3dsmax's Arch & Design Material in mentalray Renderer
• 3dsmax's VrayMtl Material in Vray Renderer

Here's an example file to make a scene like the image above using 3dsmax's mentalray Renderer: aniso_shader_mr.zip (Requires 3dsmax 2008 or later, mentalray)

Create an Arch & Design material, set it up as blurred raytraced chrome, and now set Anisotropy to a number lower than 1, the lower the number the more stretched the reflection. Also note, I placed a stretched noise in the reflection amount just to get something that looks a little bit like scratches. But note, these scratches aren't distorting the reflection, the anisotropic controls are.

Here's an example file to make a scene like the image above using 3dsmax's Vray Renderer: aniso_shader_vray.zip (Requires 3dsmax 2014 or later, Vray)

Anisotropic Brushed Metal Using A Reflection Map

Similar to the first example, but you use a pre-distorted reflection to make it appear as though it's anisotropic. So say we have the following reflection map...

That produces the following reflection on our cylinder...

Now take this reflection map and use the motionblur filter inside photoshop on it going vertically, amount depends on how much of the effect you're after. You get something like this...

Now the reflection looks anisotropic, although it's not the surface causing the anisotropy (like in real life), but the reflection itself that's been pre-blurred to appear anisotropic...

And now add a little noise in the bump slot (or even the diffuse slot if you'd like) to simulate the grain you see in anisotropic metal.

Note, the noise doesn't have to be as small as the noise I used in the "Brushed Metal Using Small Bumps" above, because we're not using the bumps to distort the reflection, we're just using the bumps to look bumpy.

Also note, the direction of the grain should always go in the opposite direction that the reflections are stretched. This happens automatically when you're actually using the grain to distort the reflections, but you need to keep this in mind when doing this sort of cheat.

Of course, this trick only works with a reflection map, you can't use it to distort real raytraced reflections. But you can mix and match, do a pre-distorted environment map and then mix it with real blurred raytraced reflections.

This site is ©2023 by Neil Blevins, All rights are reserved.