TYPE: Object
TITLE: Light Object

Light Objects are objects which cast light on other objects. 
You can also view and render from their viewpoints.

Parameters:
Transform
    Transform Order   - Order of transformations.
    Rotate Order      - Order of rotations.
    Translate         - Translation along xyz axes.             /tx /ty /tz
    Rotation          - Degrees rotation about xyz axes.        /rx /ry /rz
    Scale             - Non-uniform scaling about xyz axes.     /sx /sy /sz
    Pivot             - Local origin of the object.             /px /py /pz
    Scale             - Uniform scaling about xyz axes.         /scale
    Look At           - Object to point to.
    Path Object       - Object's path to be followed.
    Roll              - Object's rotation in degrees along path.   /roll
    Position          - Position along object path.                /pos
                        Higher/lower values allow multiple
                        trips along the path.
        0 - starting point
        1 - ending point
    Parameterization  - The type of the path curve parameterization,
			which determines the way the Position parameter is
			interpreted.			    /uparmtype
	Uniform -    The Position is used as a parameter value in the
		     unit domain of the curve.
	Arc Length - The Position is used as a fraction of the
		     total path length.
    Orient Along Path - Whether to orient the camera to the path
			or leave it unoriented.             /pathorient
    Up Vector         - Orientation of object along xyz     /upx /upy /upz
                        axes.
    Auto-Bank Factor  - Rolls object based on path curvature/bank.  0
                        means off.

Shading
    SHOP Light        - Defines the illumination shader for rendering
    SHOP Shadow       - Defines the shadow/occlusion shader for rendering.
    SHOP Emitter      - Only used by Mental Ray to emit photons
    Shadow Mask       - The list of objects which cast shadows from
                        this light.
    Depth Map         - The style of depth map to generate from this
                        light source.  Mid-Point z-depth shadows help
                        to eliminate self shadowing artifacts, but do
                        not accurately represent the distance to the
                        occluding object and so should not be used for
                        atmospheric lights.  Currently only RIB
                        generation supports deep shadow map
                        generation.
    RIB Shadow Style  - The type of shadow map for RIB renders
    Z-Depth Samples   - The number of samples to use in generating
                        the shadow map (currently only supported for RIB)
    Z-Depth Blur      - Whether to output motion blur information for
                        the shadow map generation (currently only supported
                        for RIB).
                        The style of blur defined in the output driver
                        will be used.
    Area Shape        - Currently only used by Mantra and Mental Ray
                        to represent area lights.
    Area Size         - A scale applied to the area shape.  By
                        default, most shapes are unit sized.
    Area Samples      - Number of samples used in anti-aliasing the
                        penumbra of the area light.
    Diffuse Contrib.  - The light contributes to diffuse illumination.
    Specular Contrib. - The light contributes to specular illumination.
    Photons Direct.   - When emitting photons from a light source,
                        mantra will typically force photons which hit
                        diffuse surfaces to bounce at least one time.
                        This allows photon maps to be used for
                        secondary illumination without having to pull
                        shader tricks.  Turning this toggle on will
                        cause photons to be stored in maps even on the
                        first intersection with other surfaces.
    Active Radius     - When the scene contains a large number of
                        light sources, shading can get bogged down
                        when computing illumination.  This option
                        allows mantra to "cull" lights which are
                        farther than the far clipping plane away from
                        the surface being shaded.  Caution should be
                        used with this parameter since without careful
                        use of attenuation, shading discontinuities
                        may be generated.

No SHOP
    Overview          - This section of the light's parameters will be used if
                        no SHOP is specified for lighting or shadowing.  The
                        parameters defined here will be used to generate an
                        appropriate shader description for the target renderer.
    Light Color       - The color of the light
    Dimmer            - A multiplier on the light color.  If the value
                        of the dimmer is 0, the light will be ignored
                        by renderers, thus this parameter also
                        provides a mechanism for turning off lights
                        for rendering.
    Shadow Shader     - In the absence of a SHOP shadow shader, this
                        parameter will tell mantra why type of shadows
                        should be generated by the light.
    Cone Light        - Specifies cone angle parameters
    Attenuation       - There are two styles of attenuation supported.
                        "Half intensity distance" will set the
                        attenuation curve such that at the distance
                        specified, the illumination of the light will
                        be exactly half the value specified by the
                        parameters.  Physically accurate attenuation
                        uses one over R squared falloff.
    Shadow softness   - When using zShadows without a SHOP shadow
                        shader, this parameter defines the shadow
                        softness.
    R-Map Scale       - This parameter defines a scale to be applied
                        to the reflection map on the light source.
    Reflection Map    - A reflection map to be applied to the specular
                        lighting of scene.  The orientation of the
                        light source affects the orientation of the
                        light source (translation doesn't matter).
    Diffuse Map       - A reflection map to be applied to the diffuse
                        lighting of scene.  The orientation of the
                        light source affects the orientation of the
                        light source (translation doesn't matter).
    Projector Map     - A gel in front of the light source
    Clamp Projected Map To Frustum - Turns off the tiling of the projected map.

RIB Shading
    RIB Shader        - This parameter allows you to specify a shader
                        if no SHOP is specified.

MentalRay Shading
    Energy            - This is the energy used for photon map
                        generation (for either caustic or global
                        illumination).
    Exponent          - This parameter determines the exponential
                        falloff for photons emitted from the light
                        source for caustic or global illumination
                        photon mapping.
    Caustic Photons   - The number of photons to store/emit for caustics
    Global Photons    - The number of photons to store/emit for global
                        illumination.
    
Viewing
    Projection        - Type of projection.
    Ortho Width       - Width of orthographic view volume.      /orthowidth
    Resolution        - Resolution of rendered image.
                        Standard presets are available.
    Pixel Aspect      - Pixel aspect of intended display device.
    Focal Length      - Camera focal length (zoom).             /focal
    Aperture          - Camera aperture.                        /aperture
    Shutter Speed     - The portion of the frame interval       /shutter
                        that the camera shutter is open.
                        Used to determine motion blur. [0,1]
    Near              - Position of near clipping plane.        /near
    Far               - Position of far clipping plane.         /far
    Focus             - The lens focal distance and distance    /focus
                        from the camera at which objects will 
                        be in focus. If the fstop channel is 
                        also used, objects outside this distance 
                        will be blurred.
    F-Stop            - Lens fstop. Determines blurriness of    /fstop
                        depth-of field effects.
    Lens Curvature    - Lens curvature distortion.  Simulates   /curvature
                        wide angle or fish eye lenses if set 
                        greater than 1.

Crop
    Window X/Y        - Define the centre of the window during  /winx /winy
                        the rendering process.
    Window Size       - Dimensions for expanding the cropped    /winsize
                        area specified by the resolution.
    Window Roll       - Amount the window area rolls in degrees. /winroll

Render
    Motion Blur       - Style of motion blur (for supported renderers)
    Display           - Whether the light shows up in the viewport.
                        Please see the help on the dimmer channel for
                        turning lights on/off.
    Point Instancing  - Turning this option on will cause the light
                        shader to be instanced at all the points of
                        the geometry specified.  If no geometry is
                        specified, then the light's Render SOP will be
                        used to determine what the points are.  The
                        transformation of the light source is added to
                        each point's transform.  Standard Houdini
                        transform instancing is used (with the
                        exception of the particle scale attribute).
                        It is possible to override the light or shadow
                        shader at each instance by adding a Shader SOP
                        and defining point attributes to specify the
                        shaders.
    Pre-Include       - A file or command to be inserted before the
                        light is declared in the render stream.
    Post-Include      - A file or command to be installed after the
                        light is declared in the render stream.

Misc
    Selecting Enabled - Object is capable of being picked in viewport.
    Select Script     - Script to run when the object is picked.

Local Variables
    IPT         - This is typically -1.  However, if the light is
                  being instanced, then this variable will be set to
                  the point number where the light is being instanced.
