Define

The Light->Define command is available in all modules except Tools. It allows you to define all settings for a new light. When you choose this command, the Create Light dialogue box is displayed.

Parameters

Prefix

You can add a prefix to the light name.

Light

Displays the default name of the light. You can change this in the Light text box to give it a new name.

Type

Infinite

Sets a light source that is infinitely far from the objects in the scene. There is no position associated with the light, only a direction. It is shown as a ball on a vector attached to the origin, which allows you to define the direction the light is coming from.

Point

Sets an omnidirectional light. Light rays travel in all directions from the position of the light. It is shown as a light bulb, the default light type.

Spot

Sets a unidirectional light. Light rays travel in a cone from the position of the light towards the spotlight interest. It is shown as a movie spotlight with barn doors and an interest.

Sun

The sun is an infinite light whose direction vector is derived from a physical simulation based on the latitude and longitude of the scene location and the specified time, day, date, month, and year (see the Position option).

Position

Displays the Sun Position dialogue box.

Observer's Location

Calculates the position of the sun relative to the scene location specified.

• Name: The scene location name. Click the Predefined Locations Load button for a list.
• Latitude: The scene location latitude.
• Longitude: The scene location longitude.

Predefined Locations

Allows you to access a list of locations, and save new locations to the list.

• Load displays the Predefined Locations dialogue box.
  
  You can select a location from the list, and then click Ok. The selected location's parameters are then displayed in the appropriate Observer's Location text boxes.
  
• Save saves the current scene location to the Predefined Locations list.

Time and Date

Sets the hours, minutes, day, month, and year for the scene, and calculates the exact position of the sun accordingly.

Seasonal Position

Click Load to display the Seasonal Position dialogue box. You can select one of the four seasonal sun positions, calculated according to the sun position on the first day of each season in a specified year.

• Position displays the four seasonal sun positions.
• Date displays the first date of each season from which the sun's positions are calculated.

Colour

Sets the colour of the light. Drag the slider for each colour component (range 0, 1) or type the value in the text boxes. By default the colour model is RGB, but you can click the RGB button to toggle between RGB, HSL, and HSV colour models (see Colour Sliders).

You can also click the Palette button to create, save, or use your own defined colours. See Palette for more information on using the palette.

Selective Light

Defines the light as selective. You can then pick the objects it affects or does not affect.

Include

Only objects associated with the light are illuminated.

Exclude

Objects excluded from the light are the only objects in the scene that are not illuminated.

Point and Spot Options

Start and Falloff

Specifies the point at which the light intensity starts to decrease in all directions. This option is only for the Point and Spot types of lights. The falloff for the Start Falloff and End Falloff options are measured in SOFTIMAGE units.

End Falloff

Specifies the point at which the light intensity is not visible. This option is only for the Point and Spot types of lights.

Cone Angle

Sets the angle in degrees of the cone for the Spot type of light.

Spread Angle

Sets the angle in degrees of decreasing light around the Spot light cone.

Area Light (mental ray)

The area lights are used only with the mental ray renderer (see mental ray). You must also have either a Point or Spot light type selected.

Area lights bring more realistic effects to light sources by modelling them as pieces of geometry, which allows soft shadows to be created. This is unlike the regular light types (spot, point, sun, and infinite) which perform sampling from one point, which is the light source.

Geometry

You can choose from three shapes of geometry areas to create around the light source. The shape and size of the geometry area influences the resulting form of the shadows, as well as their relative "softness" (that is, the relation between the shadow's umbra and penumbra areas). The shape and size of the geometry affects the percentage of samples that hit the light from any point in the scene.

• Rectangle creates a rectangular area of geometry around the light. The light icon appears with a rectangle around it.
• Sphere creates a spherical area of geometry around the light. The light icon appears with a sphere around it.
• Disk creates a circular area of geometry around the light. Unlike the sphere, there is no z-axis defined for Disk. The light icon appears with a circle (disk) around it.

Note:

You cannot have the geometry area defined anywhere except centered around the spotlight because the translation of the light is applied equally to the geometry area.

After you define the area light's parameter and click Ok, you can scale or rotate the geometry area icon:

• To scale, use the Scale menu cells as you would with any object.
• To rotate, select the geometry area icon by middle-clicking it. The geometry area icon turns red indicating that you can apply a rotation to it using the Rotation menu cells as usual. If the Relative Orientation option is not selected, the rotation is performed relative to the global coordinate system; if this option is selected, rotation is relative to the spotlight's local coordinates. The z-axis of the local coordinates is defined by the spotlight's position and its interest's position.

Note:

The effect of rotation has no effect on a Sphere geometry area type.

Area Sampling

Controls the number of times the light is sampled to determine the illumination for a point in the scene.

• u controls the number of samples in the u direction (longitude).
• v controls the number of samples in the v direction (latitude).

Relative Orientation

This option specifies how rotation is performed on the geometry area of the spotlight: if you do not select the Relative Orientation option, the rotation is performed relative to the global coordinate system; if you do select this option, rotation is relative to the spotlight's local coordinates.

This option is only available if you select the Spot light type.

Shadows

No Shadows

No shadows are created.

Raytraced

Creates raytraced shadows. Raytracing involves calculating light rays that are reflected, refracted, and obstructed onto surfaces. Although it gives very realistic results, it can be a time consuming process.

You can also set the Umbra Intensity level with this option selected. For more information on raytracing, see Ray Tracing.

Depth Map

Uses a modified z-buffer algorithm to create shadows more quickly than with raytracing, which is not as precise. This algorithm calculates colour and depth (z) information for each pixel based on its surface and distance from the camera. Before rendering starts, a depth map is generated for the light. This map contains information about the scene from the perspective of the light origin; this information describes the distance from the light to objects in the scene and the colour of the shadow on that object. During the rendering process, the map is used to determine if an object is in a shadow.

This option only works with the Spot type of light. You can then set the Map Resolution factor with this option selected.

Soft

Creates soft shadows by creating a penumbra area. The penumbra part of a shadow is considered the "secondary" shadow which is cast when only part of the light is blocked by the object. This option is only available with the Spot type of light. You can then set the shadow's Penumbra Factor, Umbra Intensity, Map Resolution, Filter Size, and Filter Step factors.

Umbra Intensity

Applies a transparency factor on the umbra shadow area's range (0 = black shadow, 1 = no shadow).

The umbra shadow area is considered the "main" shadow that an object casts when it blocks the light source completely.

Penumbra Factor

Creates a "fringe" area of shadow at the edge of the umbra shadow area. The penumbra part of a shadow is considered the "secondary" shadow which is cast when only part of the light is blocked by the object. You can change the transparency of this area by changing the factor from 0 (black) to 1 (no shadow). This option is only available if you select the Soft shadow type.

Map Resolution

Determines the resolution of the shadow map computed.

Filter Size

This is the size, in pixels, of a box filter used to soften the penumbra shadow edges. This option is only available if you select the Soft shadow type.

Filter Step

This is the pixel offset used to apply the filter at a specific number of pixels from the previous application. This option is only available if you select the Soft shadow type.

mental ray

The options in the mental ray area let you define light shaders for one or more selected objects used when rendering with mental ray.

For a description of shaders, see the Using Shaders section of the Rendering User's Guide.

• Shader opens the light shader database. After you have selected a shader, you can activate or deactivate it with this option.
• Select opens the Load browser to the LIGHT_SHADERS chapter.
  
  Select the shader from the database and click Load. This shader name appears in the text box below the Shader option.
  
  If you need to search for a shader, click the .. (two dots) at the top of the browser and select the appropriate chapter.
  
• Edit: If you want to save the shader by another name and then edit the parameters, you can modify its name in the text box in which it appears. This creates a new shader with the new name, but with the current parameters. To edit the shader's parameters, click Edit, which displays the dialogue box containing the shader's parameters which you can edit.

The new shader can then be saved and recalled by name in other scenes.

Key

Sets a keyframe to animate the current light settings. Parameters to be keyframed are displayed with a double border. Without exiting this dialogue box, you can use the time line pointer to change the current frame to set other keys.

Last updated 02-apr-1998