Creating a light rig is a good way to recreate image-based lighting, but with conventional lights. For more information about image-based lighting, see Using Environment Maps to Light a Scene
[ Texturing ].
Creating a Light Rig from an Image
You can match the lighting from a still image by creating a light rig based on the image’s lighting characteristics. The light rig is a set of infinite lights whose colors, directions, and intensities simulate the lighting in the source image. Because the lights are infinite, scene objects are lit the same way regardless of their locations and you don’t have to worry about positioning the lights or resizing the rig.
|
Creating a light rig is a good way to recreate image-based lighting, but with conventional lights. For more information about image-based lighting, see Using Environment Maps to Light a Scene |
The source image must be either an .hdr or .pic image, and works best if it is a spherical map. It’s also important that the image has a enough contrast between the highlights and lowlights.
Using an .hdr image produces better, more accurate lighting with a larger range of contrasts. For more information about High Dynamic Range images, see Using High Dynamic Range (HDR) Images [ Texturing ].
|
Generally speaking, it is better to use a low-resolution image because it contains all the necessary lighting information, but requires less processing time. |
How the Light Rig is Generated
A light rig is generated based on the source image’s luminance information. First, the image is divided into a specified number of “layers” of luminance. Each layer is turned into a matte in which lit regions are white and unlit regions are dark. The layer’s lit areas are then turned into lights in your scene, based on their size (amount of luminance) and proximity to one another in the layer.
You can generate a light rig from the Get > Primitive > Light menu. You are prompted to select a source image before the rig is generated.
To create a light rig using an image
1. From the Render toolbar, choose Get > Primitive > Light > Light Rig from Image to open the Light Rig Builder Options dialog box.
2. Enter the name and path of the source image in the Image File text box or click the (...) button to open a browser from which you can select the image.
The source image must be an .hdr or .pic image.
3. Set the following parameters to configure the light rig:
- Number of Layers specifies the number of luminance layers to create. Higher values require more memory and processing time. In most cases, a value of 3 to 5 is sufficient.
- Layer Luminance Extraction specifies the amount of luminance required to turn a lit area of a layer into lights in the scene. Higher values create more lights and vice-versa.
- Light Distance specifies the distance between rig lights in the scene based on the lit areas in the layer from which the lights are created. Lower values create more lights spaced more closely together and vice
4. Click OK to generate the light rig. The Light Control property editor is displayed. You can use the light control options to adjust the rig’s lighting (see Controlling Rig Lighting).
Locating the Light Rig and its Components
Once you create a light rig, it appears in the scene’s hierarchy as a null. Each light in the rig is a child of the LightRig null. The LightControl node is also a child of the Light Rig null. Click it to open the Light Control property editor from which you can adjust the lighting for the entire rig.
A light rig usually contains a large number of lights (often more than 20), and as you might imagine, adjusting each light can take a long time. Fortunately, you don’t have to. Instead, you can use the Light Control property editor to adjust the intensity and color of every light in the rig at the same time.
To adjust lighting for a rig
1. If you just created the rig, the Light Control property editor opened automatically.
Otherwise, click the LightControl node, located under the LightRig null in the explorer, to open the property editor.
2. Adjust the following lighting parameters, as necessary:
- Coarse Intensity controls coarse adjustment of all of the lights’ intensity values. Use it to make large-scale adjustments to the intensity.
In most cases, you’ll probably want to keep this value as low as possible, since the large number of lights in the rig create very bright overall lighting, even if each light’s individual intensity is not particularly high.
- Fine Intensity controls fine adjustment of all of the lights’ intensity values. Once you have set the overall intensity, use this parameter to make smaller-scale adjustments.
- Desaturate removes color from the lights. The higher the value, the less color the lights have.
Autodesk Softimage v.7.5