Object Lights with Mental Ray
Maya 2012 Tutorial
How to Use an Object to Light Your Maya Scene with Mental Ray
With Mental Ray you can turn any object into a light source. The trick is to disable the default lighting, assign your light object a Surface Shader and use the mib_cie_d node.
Add a polygon plane to the workspace by choosing Create > Polygon Primitives > Plane.
Add a text object by choosing Create > Text (include options).
In the text options, enter the text, set a font, choose Bevel for Type and adjust the bevel settings. Click Create to add your text.
Use the Scale tool (r key) to enlarge the plane object.
Using the Move tool (w key), position the text so it sits on the floor object.
Add a NURBS plane by choosing Create > NURBS Primitives > Plane. This will be the window light source.
Using the Move tool (w key) and Rotate tool (e key) to move the plane to the side to simulate a window illuminating the scene.
Select the new window plane object, then right-click the new plane and choose Assign New Material > Surface Shader.
In the Attribute Editor, surfaceShader tab, click the checkerbox next to the Out Color slider.
In the Create Render Node, Mental Ray category, Mental Ray Lights section, click the mib_cie_d icon.
Click the Render Settings icon, then select Mental Ray from the Render Using pull-down menu.
Click the Quality tab, then choose Production from the Quality Presets pull-down menu.
Click the Features tab, then open the Rendering Features section and click the Final Gathering checkbox.
Click the Common tab, Render Options section and de-select the Enable Default Light checkbox.
Click the perspective window, then click the Render Current Frame icon.
If the scene is too dark, select the window object and open the Attribute Editor. Click the surfaceShader tab, then click the Out Color right arrow to view the mib_cie_d options.
Increase the light Intensity value and re-render your scene. It may take a few adjustments to get the lighting correct. Another way to brighten your scene is to increase the size of your window object or move it closer to the scene.
Lighting with a Big Sphere
Using this method you can light a scene with a single large globe. The sphere needs to be larger than the entire scene. Assign the sphere a Surface Shader (Step Eight) and disable the default light (Step Fourteen).
With the sphere selected, open the Attribute Editor, sphereShape tab, Render Stats section. Deselect Cast Shadows, Receives Shadows, Motion Blur, Primary Visibility, Smooth Shading, Visible in Reflections, and Visible in Refractions. In the Mental Ray section, deselect Visible in Transparency, Transmit Transparency, Trace Reflection and Transmit Refraction.
Render your scene with Mental Ray, Production Quality with Final Gathering activated.
Adjusting the Light Temperature
The mib_cie_d options also include a temperature slider lower values make the light yellow and higher values turn it blue. A value of 3200 is similar to a tungsten light, 6000 is sunlight and 7000 creates a blue cast.
Improving the Light Detail
To improve the light, open the render options, Indirect Lighting tab and open the Final Gathering section. By increasing the Accuracy setting you will improve the overall quality of the light.
Can't Find Mental Ray?
If Mental Ray doesn't appear in the Render Settings, Render Using: menu, choose Window > Settings/Preferences > Plug-in Manager. Make sure Mayatomr.bundle is loaded.