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Activating caustic light effects

From: Lighting and Rendering with mental ray in Maya

Video: Activating caustic light effects

The term 'caustics' refers to the patterns of light that are created when light passes through a refractive surface, such as glass. So as you can see in this render, I have a glass vase here on the table, and light is passing through it, and we're getting this pattern in the background, and these are what's known as caustics. You can create this effect using Global Illumination. In this movie, I'll show you how to activate caustics in the scene. So, I'm going to store this image and minimize the render view, and so here's my scene, and I'm going to do a render to see how it looks so far.

Activating caustic light effects

The term 'caustics' refers to the patterns of light that are created when light passes through a refractive surface, such as glass. So as you can see in this render, I have a glass vase here on the table, and light is passing through it, and we're getting this pattern in the background, and these are what's known as caustics. You can create this effect using Global Illumination. In this movie, I'll show you how to activate caustics in the scene. So, I'm going to store this image and minimize the render view, and so here's my scene, and I'm going to do a render to see how it looks so far.

So I have a transparent surface. Light is passing through it, and it's creating this type of shadow on the background. And it's a nice, transparent shadow, but in reality, it doesn't actually reflect what happens in reality, because we're seeing a very clear, well-defined shadow. This is something you might see with maybe plastic or something like that, but the shadow itself is not picking up the refraction that the glass surface has in it. So, I'm going to store this image and minimize the Render view. When you create caustic light patterns, you're going to use Global Illumination photons.

So, just like with Global Illumination, when you're trying to create indirect lighting, it's a good idea to separate your direct lighting from your indirect lighting effects. So, I'm going to have two lights. The first spotlight is casting the shadow and creating the lighting the scene. I'm going to duplicate this light and activate the caustic settings for it. So that will just be in charge of creating the caustic light pattern in the scene and not the direct lighting. So I'm going to select light in the Outliner, do Ctrl+D to duplicate it, so now the light is duplicated.

I have the light selected in the Outliner. I'm opening up the Attribute Editor to the spotLightShape2 tab. In this case, I can set the Intensity to 0, and I can set Decay Rate to No Decay. This will have no effect. I'm going to scroll down to the Caustics and Global Illumination settings in the light, and I'm going to turn on Emit Photons. I'm going to pull up my Render Settings here and switch to the Indirect Lighting tab. In the Indirect Lighting tab, there is a Caustic section underneath Global Illumination.

So I'll expand this, and I'm going to turn on Caustics, and I'll just leave the settings at their default, just to see what we get. So, I'll minimize this, and I want to change the position of the light a little bit, so I have the light selected in the Outliner, and I'm going to choose Panels > Look Through Selected Camera, so that I can see exactly what the light is seeing in the scene. Now we only need to create caustics right behind the vase here on the table, so I don't need to be pulled out this far. So I'm going to zoom in and then change the position of the light just a little bit, and in the Attribute Editor for the light, I'm going to lower the cone angle just to get a little bit tighter around the vase.

So, I'm going to switch back to the Perspective view, create a render and see how it looks. So we can see that caustics are activated, you can see the photons of light coming through. You'll also notice that the shadow now looks different. It's not 100% transparent. This is actually more realistic, if you compare it to photographs in the real world. We're going to have something that resembles an opaque shadow, but the light passing through the surface is going to be scattered in the background. The next step that we need to do is start to tune these settings so that we get more of a well-defined pattern.

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This video is part of

Image for Lighting and Rendering with mental ray in Maya
Lighting and Rendering with mental ray in Maya

59 video lessons · 7820 viewers

Eric Keller
Author

 
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  1. 3m 46s
    1. Welcome
      1m 32s
    2. Using the exercise files
      2m 14s
  2. 19m 8s
    1. What is a CG light?
      1m 22s
    2. Types of CG lights
      10m 55s
    3. Direct lighting
      4m 48s
    4. Indirect lighting
      2m 3s
  3. 53m 20s
    1. Decay rate
      6m 30s
    2. Previewing lighting and shadows
      2m 37s
    3. Creating depth map shadows
      1m 57s
    4. Troubleshooting depth map shadows
      2m 38s
    5. Shadow map overrides
      5m 30s
    6. Using the shadow map camera
      5m 31s
    7. Saving and reusing shadow maps
      2m 48s
    8. Creating raytraced shadows
      1m 56s
    9. Adding softness to raytraced shadows
      3m 42s
    10. Creating area light shadows
      5m 11s
    11. Sample: mental ray area light
      4m 23s
    12. Setting area light visibility
      8m 7s
    13. Creating soft shadows with spot lights
      2m 30s
  4. 43m 35s
    1. Setting global illumination for interiors
      2m 33s
    2. Tuning global illumination
      5m 56s
    3. Global illumination photons
      1m 12s
    4. Activating caustic light effects
      3m 28s
    5. Tuning caustic settings
      3m 35s
    6. Setting caustic light effects on metal
      2m 35s
    7. Using final gathering for indirect lighting
      2m 9s
    8. Tuning final gathering
      4m 2s
    9. Reusing final gathering maps
      3m 21s
    10. Adding light with shaders
      5m 27s
    11. Creating final gathering maps for animation
      4m 26s
    12. Combining final gathering with global illumination
      4m 51s
  5. 1h 2m
    1. Activating the Physical Sun and Sky network
      2m 33s
    2. Tuning the Physical Sun and Sky settings
      7m 18s
    3. Applying physical light shaders
      8m 54s
    4. Applying image-based lighting
      8m 57s
    5. Tone mapping
      6m 23s
    6. Applying portal light shaders
      7m 45s
    7. Creating light beams with participating media
      10m 9s
    8. Adding depth of field with the Bokeh lens shader
      10m 39s
  6. 48m 21s
    1. Introducing render layers
      6m 13s
    2. Creating render layers
      4m 28s
    3. Splitting a scene into render layers
      15m 36s
    4. Applying render layer presets
      7m 47s
    5. Setting render layer overrides
      7m 7s
    6. Creating render layer composites
      3m 52s
    7. Organizing renders with tokens
      3m 18s
  7. 42m 24s
    1. Introducing render passes
      2m 56s
    2. Comparing render passes and render layers
      6m 44s
    3. Editing render passes
      10m 41s
    4. Using appropriate materials
      5m 51s
    5. Batch-rendering passes
      5m 56s
    6. Compositing in After Effects
      6m 41s
    7. Rendering the EXR image format
      3m 35s
  8. 23m 3s
    1. Anti-Aliasing Quality
      6m 44s
    2. Setting color profiles
      2m 53s
    3. Diagnosing raytracing
      5m 7s
    4. Adjusting motion blur
      6m 57s
    5. Finding mental ray help
      1m 22s
  9. 21s
    1. Goodbye
      21s

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