Light Types

Maya, Mental Ray: Lighting

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Understanding how lights work in Mental Ray are fundamental to appealing renders. We’ve 3 main light types which borrow the Maya Light types. Directional for distant lights, sun or moon. Spot Lights for focused light. And area lights that can mimic pretty much everything else. We will also work in linear light which is mandatory for realistic lighting these days. See the tutorials on Linear Light in a previous class.

For each light type it’s important to understand a handfull of settings, how to setup the correct amount of falloff and intensity, how to control shadow blur and sampling. Maya’s area and spot lights can also be converted to Mental Ray Area lights which bring up new list of settings and we want to make sure our lights have been converted to Mental Ray where ever possible. At last we have the portal light which is a modified version of the Mental Ray area light, the portal light is important for window lit interiors.

It’s also good to remember that lighting with an actual light source in Maya is referred to as “Direct Illumination” or “Direct Light” this is a very different system “Indirect Lighting” which is the bounce light in our scene. This can also refer to shaders such as in the newer Mental Ray Uber Shader the “MILA shader”.

Unfortunately the default light settings are rarely what we want nor are they intuitive. But once we learn a few settings we can light with a lot of power.

1. Introduction and Setup (5:55 mins)

Here we go over the different light types in Maya and setup the scene with linear workflow.

VIDEO 1.1 : INTRODUCTION AND SETUP (5:55 mins)

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The introduction and scene setup with linear workflow for this tutorial. See other tutes for more detailed info on Linear Workflow.
2. Light Types in Mental Ray (30 mins)

Mental Ray uses the Maya Lights, the main lights are Area, Spot Light and Directional Lights. It’s important to note that we can switch the area and spot lights to a Mental Ray Light type.

Each light has various settings for falloff, shadow softness and sampling and intensity.

Mental Ray is a little strange in that when we adjust the falloff type to Quadratic (which is the realistic setting) the light intensity values can get very high.

VIDEO 2.1 : DIRECTIONAL LIGHTS (7:17 mins)

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Direction Lights mimic sunlight and moonlight, lights that are so far away that we might as well treat the light rays as if they are parallel. In real life all light sources come from an area, but to save us actually creating a light the size of a sun and placing it many units away the directional light is the easy option.

Unlike other lights directional don’t have light falloff. We can also adjust the shadow blur/softness under the raytraced shadaw section

Attribute Editor
Ray Traced Shadow Attributes > Light Angle

The sampling quality of the soft shadows is found in the
Ray Traced Shadow Attributes > Shadow Rays

Directional Lights aren’t converted to Mental Ray light types, it’s fine to leave them as is.

VIDEO 2.2 : AREA LIGHTS (16 mins)

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Area Lights can be used for any earth based light, Depending on the intensity and scale and light shape they can mimc most regualr light types.

Set Quadratic falloff to make realistic. We have no blur value for these lights as they’re realistic. It’s also best to set the lights to Mental Ray lights and then the sampling value become the

Area Light Shape Node > Attribute Editor
Attributes > Decay Rate > Quadratic
Attributes > Intensity (numbers can become very large)

To make the light into a Mental Ray Light
Area Light Shape Node > Attribute Editor
Mental Ray > Area Light > Use Light Shape On

The sampling quality of the soft shadows is found in the
Area Light Shape Node > Attribute Editor
Mental Ray > Area Light > High Samples

VIDEO 2.3 : SPOT LIGHTS (6:38 mins)

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Spot Lights can be used much like area lights except we can fos the rays mor into a cone shape as a spot light or a torch would do. We can also change these lights to Mental Ray area Lights and it’s worth doing so.

Set Quadratic falloff to make realistic. We have no blur value for these lights as they’re realistic (if switched to Mental Ray Area Lights). It’s also best to set the lights to Mental Ray lights and then the sampling value become the High Samples.

Spot Light Shape Node > Attribute Editor
Attributes > Decay Rate > Quadratic
Attributes > Intensity (numbers can become very large)

To make the light into a Mental Ray Light
Spot Light Shape Node > Attribute Editor
Mental Ray > Area Light > Use Light Shape On

The sampling quality of the soft shadows is found in the
Spot Light Shape Node > Attribute Editor
Mental Ray > Area Light > High Samples

3. Creating The Interior Room (4:18 mins)

Now well move onto the next part of this tutorial which centers more on interior lighting. Interiors are much harder to light generally than exteriors where we usually light with a simple HDR light dome. Interiors have a number of challenges for bounce lighting and so lets get started and setup the scene.

VIDEO 3.1 : CREATING THE INTERIOR ROOM (4:18 mins)

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Andrew demo’s the modelling of a very simple interior.
4. Camera Exposure – Photographic Lens Shader (4:01 mins)

In the real world we can open a camera’s lense or lengthen the shutter time to brighten the image. In Mental Ray we can also adjust our exposure. One way is in the render view but the other is done by simply creating a “photographic lens shader” through the camera settings.

VIDEO 4.1 : CAMERA EXPOSURE – PHOTOGRAPHIC LENS SHADER (4:01 mins)

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Andrew creates a lense shader to adjust exposure.
5. Portal Light Setup (18 mins)

Portal Lights are a must for lighting rooms lit by windows. The portal light acts like a conductor of the outside light turning the outside values into a direct area light. This improves the quality of the light being bounced from outside which can be difficult to achieve with Final Gather alone.

VIDEO 5.1 : INCORRECTLY USING AN AREA LIGHT AS A WINDOW (5:04 mins)

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Here Andrew demo’s using an area light as a windo light. With the default values the lighting effect is more of a cinema TV Screen lighting look.
VIDEO 5.2 : PORTAL LIGHT SETUP (12 mins)

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Now Andrew demo’s the portal light setup, letting the light from the outside flow through the area light in the window and correctly lighting the interior.

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