The Light Attribute Node

The Light Attribute Node is used to specify parameters that are not contained in the light shader. For instance, several light shaders can use shadow maps; the Light Attribute Node can be used to generate these shadow maps. When there are no light attribute node attached to a light, 3Delight for Maya will do its best to extract relevant parameters from the Maya light node.

Light attribute nodes are created empty. Attributes can be added and removed by using the Add / Remove Attributes button. ⟨Left-Click⟩ on this button brings up the Add / Remove Attributes Window, which is better suited for multiple attribute addition or removal (see The Add / Remove Attributes Window). ⟨Right-Click⟩ on the Add / Remove Attributes button offers the same functionality through popup menus, which are more convenient when only one attribute or attribute group needs to be added or removed.

ShadowMaps 

This panel controls the shadow map generation for the attached light source.

Generate Shadow Maps 

This attribute toggles on and off the generation of a shadow map for this particular light. It is set to off by default. Note that even if this attribute is on, when the render pass used to render has its "Render Shadow Maps" attribute unchecked, no shadow maps will be rendered. Refer to Section 3.9.3.6 [Render Pass Shadow Maps], page 76.

Shadow Map Name 

This attribute specifies the filename of the shadow map and is empty by default. It can be set to a relative or absolute path and contain tokens, as explained in Section 5.5.4 [File Path Expressions], page 141. It can also be left empty, in which case a shadow map name will be generated using each of the attached light node’s "Shadow Map File Name", "Add Scene Name", "Add Light Name" and "Add Frame Ext" attributes. This name generation will occur regardless of the light node’s "Use Depth Map" or "Disk Based Dmaps" attributes. Using this method (or using the ‘<shape_name>’ expression), a single "Light Attribute Node" can be attached to several light sources and generate shadow maps for each and everyone of them, as long as they can all share the same parameters except for the file name. It is recommended to turn on the light node’s "Add Frame Ext" attribute if the "Generate First Frame Only" attribute is turned off. Refer to Section 5.5.5 [Automatic File Output Control], page 143. Note that a decent default file name is automatically generated when the "Generate Shadow Maps" toggle is turned on while the shadow map name is left empty.

Shadow Map Resolution 

This attribute specifies the image resolution for the shadow map. The default resolution is 512 x 512.

Shadow Map Shading Rate 

This attribute specifies the "Shading Rate" to be used for the rendering of this shadow map. The default value for this attribute is ‘1.0’. Note that the shading rate value entered here is not a multiplier of render pass’ shading rate; it is used “as is”. Refer to Section 3.9.3.3 [Render Pass Quality], page 61 for more information about the shading rate.

Shadow Map Type

It is highly recommended to read the discussion about shadow map types that be found in 3Delight User’s Manual; it details the pros and cons of each type. The available shadow map types are: ‘normal’ and ‘deep’ (for deep shadow maps).

Shadow Map Depth Filter

This attribute is only available when "Shadow Map Type" is set to ‘normal’. The value selected here defines what depth filter is used when rendering the shadow map. If some objects exhibits self-shadowing problems, adjust the ‘shadow bias’ value in the light shader (or the Maya light node if there are no RenderMan shaders attached to the light), or choose a different ‘depth filter’ value. The available values are: ‘min’, ‘average’ and ‘midpoint' (the latest value is a little slower to compute but is usually very good at getting rid of the self-shadowing problems).

Volume Interpretation 

This attribute is only available when Shadow Map Type is set to ‘deep’. The possible values are listed in the table below.