Inside Macintosh: 3D Graphics Programming With QuickDraw 3D /

Chapter 8 - Light Objects / Light Objects Reference

Data Structures

Spot Light Data Structure

You use a spot light data structure to get or set information about a spot light source. A spot light data structure is defined by the TQ3SpotLightData data type.

typedef struct TQ3SpotLightData {
   TQ3LightData               lightData;
   TQ3Boolean                 castsShadows;
   TQ3AttenuationType         attenuation;
   TQ3Point3D                 location;
   TQ3Vector3D                direction;
   float                      hotAngle;
   float                      outerAngle;
   TQ3FallOffType             fallOff;
} TQ3SpotLightData;

Field Description

lightData

A light data structure specifying basic information about the spot light.

castsShadows

A Boolean value that indicates whether the spot light casts shadows (kQ3True) or not (kQ3False).

attenuation

The type of attenuation of the spot light. See "Light Attenuation Values" on page 8-9 for a description of the constants that can be used in this field.

location

The location of the spot light, in world coordinates.

direction

The direction of the spot light. Note that the direction is defined as a world-space vector away from the light source. This vector does not need to be normalized, but vectors returned by QuickDraw 3D in this field might be normalized.

hotAngle

The hot angle of the spot light. The hot angle of a spot light is the half-angle, measured in radians, from the center of the cone of light within which the light remains at constant full intensity. The value in this field is a floating-point number in the range 0.0 to º/2, inclusive.

outerAngle

The outer angle of the spot light. The outer angle of a spot light is the half angle, measured in radians, from the center of the cone of light to the edge of the light's influence. The value in this field is a floating-point number in the range 0.0 to º/2, inclusive, and should always be greater than or equal to the value in the hotAngle field.

fallOff

The fall-off value for the spot light. See "Light Fall-Off Values" on page 8-10 for a description of the constants that can be used in this field.