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A light object represents a source of illumination for three-dimensional graphic objects. Lights may be either ambient, positional, directional, or spotlights. A maximum of 8 lights per view are allowed. Lights are not required for objects displayed in two dimensions.
An IDLgrLight object is an atomic graphic object ; it is one of the basic drawable elements of the IDL Object Graphics system, and it is not a container for other objects.
See IDLgrLight::Init
IDLgrLight::CleanupThe IDLgrLight:: Cleanup procedure method performs all cleanup on the object. IDLgrLight is described above.
NOTE: Cleanup methods are special lifecycle methods , and as such cannot be called outside the context of object destruction. This means that in most cases, you cannot call the Cleanup method directly. There is one exception to this rule: If you write your own subclass of this class, you can call the Cleanup method from within the Cleanup method of the subclass.
IDLgrLight::GetCTMThe IDLgrLight:: GetCTM function method returns the 4 x 4 graphics transform matrix from the current object upward through the graphics tree. IDLgrLight is described above.
Set this keyword to the object reference of a destination object to specify that the projection matrix for the View object in the current tree be included in the returned transformation matrix. The resulting matrix will transform a point in the data space of the object on which the GetCTM method is called into a normalized coordinate system (-1 to +1 in X, Y, and Z), relative to the View object that contains the light object.
Set this keyword equal to the object reference to an IDLgrModel object to specify that the returned matrix accumulate from the object on which the GetCTM method is called up to and including the specified model object.
IDLgrLight::GetPropertyThe IDLgrLight:: GetProperty procedure method retrieves the value of a property or group of properties for the light. IDLgrLight is described above.
Any keyword to IDLgrLight::Init
Set this keyword to a named variable that will contain an anonymous structure containing the values of all of the properties associated with the state of this object. State information about the object includes things like color, range, tick direction, etc., but not image, vertex, or connectivity data, or user values.
IDLgrLight::InitThe IDLgrLight:: Init function method initializes the light object. IDLgrLight is described above.
NOTE: Init methods are special lifecycle methods , and as such cannot be called outside the context of object creation. This means that in most cases, you cannot call the Init method directly. There is one exception to this rule: If you write your own subclass of this class, you can call the Init method from within the Init method of the subclass.
Properties retrievable via IDLgrLight::GetProperty
Set this keyword to a 3-element floating point vector of the form [constant, linear, quadratic] that describes the factor by which light intensity is to fall with respect to distance from the light source. ATTENTUATION applies only to Positional and Spot lights, as specified by the TYPE keyword. The overall attenuation factor is computed as follows:
attenuation = 1/(constant + linear*distance + quadratic*distance^2)
Set this keyword to a three-element vector specifying the RGB color of the light. The default is [255, 255, 255], which is a white light. The color of a light is ignored when graphics are sent to graphics destinations using the Indexed color model, in which case light intensities are scaled into the range of colors available on the graphics destination.
Set this keyword to the angle (measured in degrees) of coverage for a spotlight. The default is 60.
Set this keyword to the three-element vector representing the direction in which a spotlight is to be pointed. The default is [0,0,-1].
Set this keyword to a floating-point value that describes the attenuation of intensity for spotlights as the distance from the center of the cone of coverage increases. This factor is used as an exponent to the cosine of the angle between the direction of the spotlight and the direction from the light to the vertex being lighted. The default is 0.0.
Set this keyword to a boolean value indicating whether this light should be enabled:
Set this keyword to a floating point value between 0.0 (darkest) and 1.0 (brightest) indicating the intensity of the light. The default is 1.0.
Set this keyword to a vector of the form [ x , y , z ] describing the position of the light. By default, the position is [0, 0, 0].
Set this keyword equal to a string containing the name associated with this object. The default is the null string, ' '.
Set this keyword to one of the following values, indicating the type of light. Valid values are:
Set this keyword to a value of any type. You can use this "user value" to contain any information you wish. Remember that if you set the user value equal to a pointer or object reference, you should destroy the pointer or object reference explicitly when destroying the object it is a user value of.
Set this keyword to a vector, [ s 0 , s 1 ], of scaling factors used to convert X coordinates from data units to normalized units. The formula for the conversion is as follows:
Normalized X = s 0 + s 1 * Data X
Set this keyword to a vector, [ s 0 , s 1 ], of scaling factors used to convert Y coordinates from data units to normalized units. The formula for the conversion is as follows:
Normalized Y = s 0 + s 1 * Data Y
IDLgrLight::SetPropertyThe IDLgrLight:: SetProperty procedure method sets the value of a property or group of properties for the light. IDLgrLight is described above.
Any keyword to IDLgrLight::Init