Optical FX Attributes

The Optical FX Attributes control the appearance of glows, halos, and lens flares.

Glow Type

The type of glow the light produces when viewed directly. Click the arrow to access available glow types from the drop-down list.

A light does not need glow to illuminate objects when the scene is rendered, however a light does need glow to be visible by the camera when the scene is rendered. The default Glow Type is Linear.

The following examples show a yellow glow ( Glow Color) and all other Glow attributes left at the default settings.

None: No glow appears.
Linear: Glow slowly diminishes from the center of the light.
Exponential: Glow quickly diminishes from the center of the light.
Ball: Glow diminishes faster towards a distance (from the light center) specified by the Glow Spread value.
Lens Flare: Simulates a bright light source illuminating the surfaces of several camera lenses.
Rim Halo: Forms a circular ring with a soft central glow. The size of the ring is determined by the Halo Spread value (in this example, 0.75).

Halo Type

The type of halo the light produces when viewed directly. Halo is similar to Glow, except that the fall off is more gradual and different fall-off types are available. The default setting is None. Click the arrow to access the drop-down list.

The following show the different Halo types with the default Linear Glow Type, a red Halo Color, and the Halo Spread set to 0.75.

None: No halo appears.
Linear: Halo slowly diminishes from the center of the light.
Exponential: Halo quickly diminishes from the center of the light.
Ball: Halo diminishes faster towards a distance (from the light center) specified by the Halo Spread value.
Lens Flare: Simulates a bright light source illuminating the surfaces of several camera lenses.
Rim Halo: Forms a circular ring with a soft central glow. The size of the ring is determined by the Halo Spread value.

Glow Attributes

Glow Color: The color of the light’s glow. Click the color swatch to open the Color Chooser and select a color if desired.The default setting is white.
Glow Intensity: Also accessible through the material’s Special Effects attributes (see the Shading guide for details). Controls the glow brightness. As the Glow Intensity value increases, so does the apparent size of the glow effect. A negative Glow Intensity value subtracts from other glows. (The light’s Decay Rate controls how the glow brightness decreases with distance.) The slider range is 0 to 10, but you can enter values up to infinity. The default value is 1.
Glow Spread: Controls the size of the glow effect. Negative values can have odd but sometimes useful effects. The slider range is 0 to 5. The default value is 1.
Glow Noise: Controls the strength of two-dimensional noise applied to the glow. The noise is generated on a plane centered at the location of the light and always oriented towards the camera. The slider range is 0 to 1. The default value is 0.

To create the illusion of illuminated smoke around a glowing light source, set the Glow Noise value to about 0.5 and slowly animate the Noise Uoffset and Noise Voffset values. The smoke appears to slowly drift by the light.

TipGenerally, fog illumination is better than glow if you want to create smoke and fire effects because fog is a 3D effect (for example, glow noise cannot be occluded by objects).

The following example shows how you can create a moody night sky simply by adjusting a few Glow Attributes. The Optical FX attributes used in this example are as follows:

Glow Type = Exponential
Radial Frequency = 0
Star Points= 2
Rotation = 300

Glow Radial Noise

Randomizes the spread of the glow to simulate starburst effects and eyelashes refracting light. The slider range is 0 to 1. The default value is 0.

Negative values of Glow Radial Noise produce thicker noise. Use the Radial Frequency attribute to control the smoothness of this effect.

Glow Star Level

Simulates camera star filter effects. The slider range is 0 to 4. The default value is 0. Use the Star Points attribute to set the number of points on the star. Use the Rotation attribute to rotate the star.

Glow Opacity

Controls the amount the light’s glow obscures objects. Think of opacity as the opposite of transparency. The slider range is 0 to 0.5. The default value is 0.

Halo Attributes

Halo Color: The color of the halo. Click the color swatch to open the Color Chooser and select another color if desired. The default setting is white.
Halo Intensity: Controls the halo brightness. As the Halo Intensity value increases, so does the apparent size of the halo effect. (The light’s Decay Rate controls how halo brightness decreases with distance.) The slider range is 0 to 5. The default value is 1.
Halo Spread: Controls the size of the halo effect. Halo size is generally larger than glow size when the Halo Spread and Glow Spread values are the same. The slider range is 0 to 5. The default value is 1.

Lens Flare Attributes

These attributes are only accessible if Lens Flare is turned on in Optical FX Attributes.

Flare Color: The color of the lens flare circles. Click the color swatch and select another color from the Color Chooser if desired. The default color is white.
Flare Intensity: Controls the flare effect’s brightness. (The light’s Decay Rate controls how the lens flare brightness decreases with distance.) The valid range is 0 to infinity. The slider range is 0 to 5. The default value is 1.
Flare Num Circles: Represents the number of circles in the lens flare effect. The valid range is 0 to infinity. The slider range is 0 to 30. The default value is 20.

If the Flare Num Circles value is very large, rendering times may be long, especially if the Flare Min Size and Flare Max Size values are large and the Flare Color is textured.
Flare Min Size, Flare Max Size: The size of the circles is randomized between these two values. The valid range is -infinity to infinity. The slider range is 0 to 5. The default value is 0.1 for Flare Min Size and 1 for Flare Max Size.
Hexagon Flare: Produces hexagonal-shaped flare elements (instead of circles).
Flare Col Spread: Controls the hue amount of individual circles randomized about the Flare Color. The Flare Col Spread value has no effect if the Flare Color is not at least partially saturated (for example, not white or grey). The slider range is 0 to 1. The default value is 0.5.
Flare Focus: Controls the circle edge sharpness. The valid range is 0 (very blurry) to 1 (totally sharp). The default value is 0.6.
Flare Vertical, Flare Horizontal: Controls the axis of the flare effect relative to the center of the image. If the light source moves, the flare appears to rotate through this point. The slider range is -1 to 1. The default value is 1.
Flare Length: Controls the flare effect length relative to the light location. If Flare Length is small, all circles overlap the light. If Flare Length is large, the circles spread out across the image. The Flare Length value has no effect if the Flare Vertical and Flare Horizontal values are both 0. The slider range is 0 to 1. The default value is 1.

Noise Attributes