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Explaining diffuse reflections

From: Creating Textures and Shaders in Maya

Video: Explaining diffuse reflections

So in this movie, we're going to talk about the concept of diffuse reflections. What is a diffuse reflection? Well, we have to think of it this way. All surfaces in the real world reflect light in one way or another. If they don't, then they're completely transparent. The light passes through them and they're essentially invisible to us. So when you're thinking about this kind of thing, you want to think about how smooth is the surface, because the type of reflection that is created is dependent on the smoothness of the surface. Let's take a look at this scene. We have two teapots here on this checkerboard surface.

Explaining diffuse reflections

So in this movie, we're going to talk about the concept of diffuse reflections. What is a diffuse reflection? Well, we have to think of it this way. All surfaces in the real world reflect light in one way or another. If they don't, then they're completely transparent. The light passes through them and they're essentially invisible to us. So when you're thinking about this kind of thing, you want to think about how smooth is the surface, because the type of reflection that is created is dependent on the smoothness of the surface. Let's take a look at this scene. We have two teapots here on this checkerboard surface.

I've created two very simple shaders to illustrate the point of diffuse reflections. So I'll do a quick render here and we can compare the result. So this teapot here on the left is highly reflective. The surface is a lot like a mirror. We can clearly see the checkerboards in the background reflected on the surface of the other teapot, and even other parts of the teapot reflected on the surface. This teapot on the right is also very reflective. However, you can see that the surface is somewhat rough.

What this means is that a smoother surface is going to reflect the light much like a mirror. A rougher surface is going to reflect the light kind of like - think about concrete on a sunny day. Concrete is very rough. So when the individual photons of light hit the surface, they're reflected back in all directions. What we end up with is we see the light reflected on the surface, but we don't actually see the other objects in the scene reflected on the surface. So I've created a dynamic simulation to illustrate this point a little bit better.

Imagine this surface, this plane, as being a smooth surface. At this point, we're so close to it that we can actually see the individual photons of light. So as I play the simulation, you'll see the photons of light come in and they bounce off the surface at about the same angle that they hit the surface. This is what a smooth or highly reflective surface would look like very close. Now if the surface starts to become rough, like concrete or something like that, you'll see that the photons, as they hit the surface, they're reflected back into the environment in all directions.

In other words, the photons of light are diffused back into the environment. Hence, the term diffused reflection. So as you can see from the way that I've set up this diagram, I have it gradually becoming rougher over time. Let's just illustrate the point that surfaces have a wide range of diffusion. So, as you think of your surface is going from perfectly smooth to very rough, you'll think about how that affects the individual photons of light. So we have a range of diffuse reflection, from perfectly smooth to very, very rough and everything in between.

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This video is part of

Image for Creating Textures and Shaders in Maya
Creating Textures and Shaders in Maya

37 video lessons · 7834 viewers

Eric Keller
Author

 
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  1. 2m 19s
    1. Welcome
      1m 6s
    2. Using the exercise files
      1m 13s
  2. 17m 49s
    1. Explaining diffuse reflections
      2m 39s
    2. Defining glossy and blurred reflections
      2m 32s
    3. Looking at refraction
      4m 20s
    4. Describing the Fresnel effect
      1m 56s
    5. Understanding anisotropy
      1m 10s
    6. Identifying ambient and reflection occlusion
      1m 49s
    7. Defining sub-surface scattering
      2m 4s
    8. Simulating translucency
      1m 19s
  3. 1h 8m
    1. Using Maya's standard shaders with mental ray
      7m 2s
    2. Comparing mental ray and Maya shader nodes
      9m 12s
    3. Creating mental ray shaders
      2m 32s
    4. Making sense of mental ray shaders
      10m 35s
    5. Introducing the mia_material
      9m 16s
    6. Creating a custom mia_material preset
      9m 17s
    7. Looking at car paint materials
      6m 43s
    8. Using subsurface scattering shaders
      13m 33s
  4. 1h 5m
    1. Understanding UV coordinates
      4m 26s
    2. Comparing NURBS and polygon UVs
      4m 48s
    3. Mapping polygon UV surfaces
      13m 1s
    4. Using texture maps for color and other shader channels
      8m 1s
    5. Applying and projecting 2D procedural texture nodes
      4m 0s
    6. Applying 3D procedural texture nodes
      7m 1s
    7. Using ramp textures
      8m 12s
    8. Setting up utility nodes
      6m 29s
    9. Using file texture nodes
      9m 41s
  5. 22m 36s
    1. Applying the turbulence texture
      9m 37s
    2. Considering the round corners texture
      4m 17s
    3. Improving skin detail with ambient occlusion
      4m 27s
    4. Applying reflection occlusion
      4m 15s
  6. 33m 6s
    1. Painting bump maps
      4m 14s
    2. Creating normal maps
      5m 24s
    3. Applying normal maps
      6m 17s
    4. Creating displacement maps
      9m 14s
    5. Troubleshooting displacement maps
      7m 57s
  7. 33s
    1. Goodbye
      33s

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