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Adding light with shaders

From: Lighting and Rendering with mental ray in Maya

Video: Adding light with shaders

One of the more interesting aspects of working with Final Gathering and rendering with mental ray is that light objects, objects with shaders that have an incandescent value, can actually add light to a render without the help of any other direct lighting. So, to demonstrate this, I'm using this simple animation of a lava lamp. I have my lava lamp in the scene, and if I scrub on the timeline, you can see that these little guys are animated, moving around inside the lamp. So, I'm going to go to my Render Settings window. That's Window > Rendering Editors > Render Settings.

Adding light with shaders

One of the more interesting aspects of working with Final Gathering and rendering with mental ray is that light objects, objects with shaders that have an incandescent value, can actually add light to a render without the help of any other direct lighting. So, to demonstrate this, I'm using this simple animation of a lava lamp. I have my lava lamp in the scene, and if I scrub on the timeline, you can see that these little guys are animated, moving around inside the lamp. So, I'm going to go to my Render Settings window. That's Window > Rendering Editors > Render Settings.

The first thing I'm going to do is go to the Common tab and turn off the default light. I'm turning this off, so there are no extra lights affecting the scene. So if I create a render now, I should see basically a dark room. There is nothing in here, because there is no lighting. So now, the next thing is go to the Indirect Lighting tab. I'm going to turn on Final Gathering. These are the default settings right here. I'm going to pump this up a little bit. So, let's set the Accuracy to 200, just to get something that looks all right to start with.

I'm also going to increase the Secondary Diffuse Bounces, so we get a little bit more light moving around in here. I'll set this to 1. Then what I need to do is apply a shader to the lava inside the lamp, to make it actually glow. So, I'm going to expand the lava group, so we can see our little bits of lava geometry in here. I'm going to select the first one and Shift+Select the last one, so that they are all selected. I'll just click on this Lambert Material icon, here in the Rendering shelf.

I'm going to just change a couple of settings here. The first thing I'm going to change is the color. I'm going to change this to a purplish color. Then I'm going to click on this and add a light purple to this value, and make it fairly bright, so it's a bright pink. So, I'm going to render that and see how that looks so far. It'll be probably be still fairly dark. We can't see that the lava is actually glowing. It's got this purple color to it. So we just need to boost a few settings to get some of that light going. So, I'm going to go into the Render settings again, and under Indirect Lighting, I'm going to click on the Primary Diffuse Scale swatch here.

So I'm just going to increase the scale. So, I have this set to HSV, which stands for Hue, Saturation and Value, so I'm just going to click on that. Under the Value slider, I'm just going to type in 4 here, just to pump up the value of the scale. So, let's do a render now and see how that looks. Now, we're starting to actually see objects in the scene. We can see that they're castings some light here on the background plane. The body of the lamp has a reflective shader here, so it's starting to pick up reflections of the lit environment.

I'm going to store that now. The next thing I'm going to do is take a look in here. I have a polygon plane that's hidden in the Outliner. I'm going to select it. This Plane1 is the background, so I'm going to select Plane2 and press Shift+H down to hide it. What we're going to see is that we have this plane here acting as kind of like a bounce card, like something a photographer might use. It's just positioned right here. This plane has a Lambert shader applied to it that is white with just a very dim gray applied to the Incandescence, just like I applied purple shading to the lava here.

So, this has got a little bit of a value in here. The other thing about the actual geometry is that if I select this geometry and go to the pPlaneShape2 tab here in the Attribute Editor, I've gone to the Render Stats, and I've turned off Casts Shadows, Receive Shadows, as well as Primary Visibility. So this plane is not actually going to show up in the render, even though we can see it here in the scene; it's not going to render at all. But the fact that it's casting light because of its incandescent shader is going to be applied in the seen. You'll also be able to see it in the reflection.

So, it's got Visible In Reflections that's left on, so you will see it in the reflection on the glass here, which will add a little bit of extra quality to the scene. So, I'm going to do another render here. You can already see that that bounce card is adding some white lighting here, even though we can't actually see it in the render. It's also being picked up in the reflection on the body of the lava lamp and then the glass. At this point, I can just mess with these settings a little bit more, maybe select one of the pieces of the lava. I'll go into the Hypershade.

I'm just going to graph the material on the lava, and here it is in Hypershade. Maybe I'll boost that Incandescent value a little bit and also add a bit of Saturation. I can actually put this above a value of 1. I can actually plug this 2, just by selecting that value and typing in 2, so we get something that's very bright. Let's see how that looks. Now it's really adding a lot more light to the scene.

So even though we don't have any actual lights in the scene, we are actually seeing the objects. This is because the shaders applied to the lava and the shaders applied to that invisible plane are both casting light into the scene. So, this is a technique that can be used for all kinds of effects. If you have something like a cylinder, a fluorescent light housing in a room, you could apply Incandescent shader and turn on Final Gathering. You'll see that that fluorescent bulb will actually add lights to the scene.

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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 · 8094 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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