Object Lights with Mental Ray

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.


Step One

Add a polygon plane to the workspace by choosing Create > Polygon Primitives > Plane.

Step Two

Add a text object by choosing Create > Text (include options).

Step Three

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.

Step Four

Use the Scale tool (r key) to enlarge the plane object.

Step Five

Using the Move tool (w key), position the text so it sits on the floor object.

Step Six

Add a NURBS plane by choosing Create > NURBS Primitives > Plane. This will be the window light source.

Step Seven

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.

Step Eight

Select the new window plane object, then right-click the new plane and choose Assign New Material > Surface Shader.

Step Nine

In the Attribute Editor, surfaceShader tab, click the checkerbox next to the Out Color slider.

Step Ten

In the Create Render Node, Mental Ray category, Mental Ray Lights section, click the mib_cie_d icon.

Step Eleven

Click the Render Settings icon, then select Mental Ray from the Render Using pull-down menu.

Step Twelve

Click the Quality tab, then choose Production from the Quality Presets pull-down menu.

Step Thirteen

Click the Features tab, then open the Rendering Features section and click the Final Gathering checkbox.

Step Fourteen

Click the Common tab, Render Options section and de-select the Enable Default Light checkbox.

Step Fifteen

Click the perspective window, then click the Render Current Frame icon.

Step Sixteen

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.

Step Seventeen

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.