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Chapter 8, Multilayer Compositing and 3D Effects
Working with Lights

Topics on this Page:

Adding Lights to a Scene

Choosing the Type of Light

Setting Basic Lighting Properties

Setting Shadow Properties

Determining How a Light Affects Shading

Adding a Projector Texture to a Light



Light is a basic geometric 3D scene element. Each light in a scene contributes to how a scene is illuminated. Lights affect the way all object's surfaces appear in the rendered scene. You can dramatically change the nature and mood of your compositions by modifying lights and their properties.

Note: You can animate lighting parameters using keyframes and by applying expressions--see Chapter 21, Animation and Chapter 24, Expressions.

Adding Lights to a Scene Top

You can add one or more lights to your scene and set their properties to achieve a variety of lighting effects. There are two ways to add lights to a scene: the Lights tab in the Reaction node or the Tools tab.

When you add a light to Reaction, you must be in the Reaction Group Schematic to view the light(s) in your scene. The light you add is positioned at 0, 0, 0, so you may need to zoom out to view the light icon.

You can also set the light type and parameters, as well as parent a light to an axis, and animate its properties.

Note: The light icon is visible only if you have selected Icons in the Render tab of Reaction.

To add a light from the Lights tab:

  1. Select the Lights tab.

  2. Under the Light list, click Add.

    A light is added to the Group Schematic and the Lights list.

  3. To view the light, double-click the Reaction node in the Schematic view.

    The Group Schematic appears.

To add a light from the Tools tab:

  1. Do one of the following to display the Group Schematic:

  2. From the Tools tab, select the Light tool from the Reaction folder and drag it to Schematic.

Choosing the Type of Light Top

When you add a light to your scene, an Omni light is added by default. You can change the light type and its properties, and add as many lights to your scene as needed.

You can define physical properties for your light, depending on the type of light you selected. There are three types of lights available.

Omni -- Simulates a point light source that casts rays in all directions from the position of the light. Similar to a light bulb, where the light rays emanate in all directions from the bulb.

Spotlight -- Casts rays in a cone, or four-sided pyramid, simulating a real spotlight. This is useful for lighting a specific object or area and creating sharp-edged shadows.

Directional -- Casts rays in a single direction, from a geometric area and is useful for creating soft-edged shadows with both an umbra (a full shadow where an object blocks all rays from a light) and a penumbra (a partial shadow where an object blocks some of the rays).

To set attributes for a Spotlight:

  1. Select the Lights tab.

  2. Under Light Type, select the Spotlight light type.

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  3. Set the Spotlight properties.

    Properties Description
    Shape The shape of the light can be a circle or rectangle.
    Hot Spot Angle The angle where the solid cone of full intensity light ends and a gradual fading begins.
    Cutoff Angle The angle at which the light ends.
    Aspect The aspect ratio of the spotlight shape.


To set properties for a directional light:

  1. Select the Lights tab.

  2. Under Light Type, select the Directional light type.

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  3. Adjust the Radius field to set the radius of the light. This value is also used to delimit the size of the shadow map.

Setting Basic Lighting Properties Top

You can set basic lighting properties for all light types.

To set basic lighting properties:
Properties Description
Color Sets the color for the light. Click the color pot to display the color picker, choose a color, and click Set--see Working with the Color Picker.
Intensity Sets the amount of light emitted by the source light.
Decay Sets the light's intensity to diminish gradually using a linear or quadratic function.
1/2 Distance Represents the distance at which the light's intensity is reduced by half.
Time Dilation Modifies the motion blur that affects lights animated in your scene. You can set the Time Dilation factor to give the light the appearance of moving at a different speed than is set for Motion Blur in the Render tab.


Setting Shadow Properties Top

You can enable shadows and set their properties and parameters to achieve the results that you want.

To enable shadows and set their properties:
Determining How a Light Affects Shading Top

You can choose the shading properties a light affects. By default, a light affects the ambient, diffuse, and specular components of shading.

To choose the shading properties that a light affects:

  1. On the Lights tab, under Parameters, select the Affects option.

  2. Under Light Affects, select the shading properties you want the light to affect.

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Adding a Projector Texture to a Light Top

A projector texture is created when you connect an image to a light node in the Reaction Group Schematic. The Projector Texture is applied in the same way as a material texture.

To add a projector texture to a light:
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