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MayaMan Light Attributes Dialog

The MayaMan Light Attributes dialog allows you to attach attributes to particular lights in your scene, so that they are rendered differently with MayaMan.

Adding and Accessing the MayaMan Light Attributes

Before you can modify the MayaMan Light Attributes, you will have to add the attributes to the lights. You do this by selecting the light(s) you want to add the attributes to, then select "Add Light Attributes" from the MayaMan menu. All attributes are stored on a separate node, so several lights can easily share the same set of attributes.

By default, "Add Light Attributes" will add one shared/common attribute node for all the lights in the selection that do not already have attributes attached to them. In the optionBox of the menu, there are alternative ways in which to add the attributes, eg adding separate nodes to each object etc.

Once a light has a MayaMan Light Attribute node, you can simply access all attribute parameters in their own panel in the Maya Attribute Editor

Depth Map Shadow Attributes

Depth Map General

One Map For All Frames

This option will result in MayaMan generating a single shadow map for the light at the beginning of a render sequence, and reusing it for subsequent frames. This can be a large time saving if the shadows are not changing over the sequence.

Custom Shadow Map

This option allows you to specify an existing shadow map to be used by this light, rather than MayaMan generating one for you.

Reuse Mode

This option let's you take fine-grained control over which shadow maps get reused and which are recomputed.

Delete Mode

This option let's you take fine-grained control over which shadow maps get deleted at the end of the render and which are saved.

Depth Map Use

Samples

The number of samples used when testing the shadow map. This can reduce the grain in the blurry areas of the shadow map. 16 is recommended as the minimum, and blurry maps can require values of 64 or more.

Filter

You can choose a filter to use when sampling the shadow map for slightly different sampling effects.

Depth Map Creation

Depth Filter

You can choose depth filtering as selected in Global Shadow Options, the global default only when the light it is not requesting MidDist, or an explicit depth filter.

Z-Clipping

Near clipping distance
Objects which are closer to the light than this value will not cast shadows.

Far clipping distance
When enabled objects which are farther away from the light than this value will not cast shadows. When disabled the value used is effectively infinite.

PRMan 11 Deep Shadows

Enables PRMan 11's deep shadow computations for this associated light.

Custom Display Driver

Normally MayaMan select the right type of display drivers for the creation of mapped shadows... very advanced users may have reason to use a custom display driver though.

Display Driver Arguments

The shadow display driver can have extra arguments added. This can be particularly useful for things like prman's pyramidal shadow map feature... just put the following in the arguments field:

	"pyramid" [1]
Note that this can be used independently of the Custom Display Driver feature.

User Defined Shadow RIB Statements

RIB statements that are only inserted into the rib for this light.

Ray Traced Shadow Attributes

Blur

Controls the focus of the ray bundle used to calculate the shadow

Bias

Controls the ray-bias used for calculating shadows, useful for avoiding self-shadowing artifacts.

Motion Blur Shadows

Just like the settings in the MayaMan Global Options, MayaMan Material Attributes and MayaMan Model Attributes, this option will output the "motionrays" attribute into the RIB file. However, when setting the attribute for a light, only shadows (ie no reflections) will be motion blurred.

Also, refer to the Entropy documentation for this option, as this attribute is handled slightly differently when declared for lights (more precisely, Entropy will render motion blurred shadows if either Attribute "light" "integer motionrays" or Attribute "render" "integer motionrays" is enabled.)

Caustics/Photon Mapping

For Air and Entropy you can set the number of photons to be shot from the light source in calculating caustics. Zero effectively turns off caustics for the light. Higher values will slow down the render. The Photons Only flag is not used.

For PRMan11 the controls are different, the number of photons is not set directly at the light source and the number here has no meaning, however, a light will only go into the photon map rib if it's 'Enabled' flag is turned on and there are a non-zero number of photons requested, this provides a way to only get photons from a certain set of lights. Sometimes it's useful to have lights in the scene that only generate photons but don't participate in regular lighting (ie: they simulate injection of photons from an environmental image), in this case turn on the Photons Only checkbox. Use the Photon Type setting to determine which photon maps a light will contribute to.

Misc

Atmospheric

This enables the __foglight parameter which is used to control the behaviour of some lights, especially their interaction with volume shaders (primarily a BMRT concept, though if the light shaders are written to look for this parameter it can be used in other renderers as well).

Motion Blur Shadows

When enabled an RiPixelSamples statement will go into the shadow map rib. When and how this is useful is left to the reader as an exercise.

Categories

RenderMan supports the concept of light categories and here is where you supply them. Use commas to seperate category names if you need more than one. For a category to actually have any effect you'll need to write your own illuminance loops.

Custom Light Shader

This section allows you to attach a custom RenderMan light shader to your light. You need to first create a MayaManCustomLight node by pressing the 'Create New Custom Shader Node' button in the dialog. If you have any existing nodes you can type their name or browse to them. This will associate the custom light shader node with this light. You then view the light using the Maya Attribute Editor to set the shader file to use and any shader parameters.

Shadow Casting Override Sets

These sets allow fine grained control over what objects contribute to shadows for a particular light (as far as depth mapped shadows goes anyhow).

Any surface in the 'On' group will cast shadows even if it is not a shadow caster. Any surface in the 'Off' group will not cast shadows.

It may be useful to use a set with more than one light... ie: an extra shadowing set applied to all key lights.

Clicking the checker icon in the attribute editor will create an empty set with an appropriate name.

Be sure to add shape nodes to the set... just as it's Maya's shape nodes that carry shadow casting information so too the override link. The sets contain full paths so individual instances of a particular shape can be in more than one set.

When drag-n-dropping a set from the Overview into the drop slot the connection editor will open, you need to connect the message output of the set to the appropriate attribute of the attributes node.

Shadow Location Cheating

This section allows renderers that supports shadow cheating to cast shadows from one (or more) lights and use those maps to control shadows for this light. The other lights don't contribute to scene illumination, they only contribute with shadow information.

Soft Shadows

This section is similar to Shadow Location Cheating but is for renderers that support soft shadows.

User Defined RIB Statements

A chunk of rib that will be inserted into the rib just after the RiLightSource call.

Additional Light Related Attributes

Ray Marching in Light Fog and Volume Fog

When a lightFog node is processed it's check for a couple of attributes which control how the raymarch quality. If the attributes don't exist they will be automatically created. MayaManStepSize is how far each integration step moves in world space, smaller values give higher quality. MayaManMaxSteps clamps the total number of steps, if the ray distance divided by the step size would rezult in more steps than this then the step size is increased regardless of the setting in MayaManStepSize.

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