Lights

Further Reading
See Lights in the Arnold User Guide
The Arnold for 3ds Max User Guide explains how to set up Arnold lights in the 3ds Max user interface. The Arnold User Guide provides the full documentation for Arnold lights.

Note:

More information about lights can be found in the Arnold User Guide.

Important:

There are some current limitations when using 3ds Max Photometric lights with MAXtoA. Here is a brief list of what is not supported:

Some light shapes do not support Spherical distribution.
Only supports ray-traced shadows – other settings are ignored.
Exclude/Include is not supported.
Incandescent lamp-color shift is not supported.
The light shape is not visible to the camera rays.
Shadow parameters are not used.
Legacy Atmosphere & Effects are not supported.

Important:

Light Path Expressions do not currently work in MAXtoA. They are planned for a future release.
Note that the Physical Scale value in the Exposure Control (Environment and Effects) has an influence over how your 3ds Max and Arnold lights render. You may need to Disable or adjust the Physical Scale to get the intensity you expect.
3ds Max scenes ( particularly architectural scenes) setup for other rendering engines will not necessarily convert well to MAXtoA. Arnold does not currently support physical units for lights, and a conversion process is not straightforward. You may need to adjust intensity and exposure parameters for your lights to match.

Tip:

Arnold does not support constant light decay. However, Arnold' s quad and disk area lights have a spread parameter, that when set to a low value, will give you something similar to a constant fall-off. Similarly, the spot_light in Arnold has a lens_radius parameter that, when set to a non-zero value, and coupled with a low angle, has the apparent effect of flattening the decay, like in a Hollywood-style searchlight. Another workaround is to use distant/directional lighting.

There is a generic Arnold Light object where you can select the type of light in a combo and the parameters will change dynamically according to the selected type. This can be found under the lights menu in the create tab.

_{Choose Arnold from the light list}

Point light
Distant light
Spot light
Quad light
Disc light
Cylinder light
Skydome light
Photometric light
Mesh light
Light filters

Common Light parameters

As well as honoring the standard 3ds Max light parameters, the Modify Panel will also show the following Arnold parameters:

Shape

Type

The shape of the light. Choose from point, distant, spot, quad, disk, cylinder, skydome, photometric, and mesh.

_{Types of lights available in MAXtoA}

Light Shape Visible

When enabled, the shape of the light is visible in the render as a self-illuminated object.

Contribution

Per-light scaling for camera, transmission, diffuse, specular, sss, indirect, and volume. Weights scaling the light contribution to each of those components independently. Should be left at 1 to produce physically accurate results.

AOV Light Group

Per-light AOVs are available via a string parameter. Each light has an AOV parameter which writes out the light contribution to a separate AOV with a corresponding name.

Cylinder Light

The cylinder_light shape simulates light from a cylindrical area source (tube shape).

Disk Light

The disk_light shape simulates light from a circular area source (flat disk).

Distant Light

This is a parallel light from a distant source, specified in terms of a direction vector. Often used to model sunlight.

Mesh Light

In situations where conventional light shapes will not suffice, mesh lights are more suitable. Mesh lights can be used to create interesting lighting effects that would not be possible any other way. For example, effects such as neon lighting or a car light motion trail effect can be achieved more easily with mesh lights.

Note:

An example mesh_light scene can be found here.

The mesh_light is provided as an alternate translator for a mesh. This means that shape parameters, such as visibility flags, and the mesh light parameters are accessible from the Modify Panel of the mesh.

Note:

NURBS surfaces do not currently work with mesh lights.

_{The mesh_light translator is available in the Modify Panel}

Note:

It is not currently possible to make a mesh_light visible to camera rays. A workaround is to add emission to a standard_surface shader assigned to the object. This will give the impression that the geometry is incandescent. Set the indirect_diffuse to 0 for the standard_surface shader assigned to mesh as the mesh_light is already emitting light. _{Setting indirect_diffuse to 0 disables GI bounces for the mesh.}

Photometric Light

Photometric lights use data measured from real-world lights, often directly from bulb and enclosure manufacturers themselves. You can import IES profiles from companies such as Erco, Lamp, Osram, and Philips; their IES files provide accurate intensity and spread data for a given light model.

Point Light

Although named point for historical reasons, this light source can model light either from a (theoretical) point source, or from a sphere (the latter being more realistic in most cases, and producing less sharp shadows). The light is cast evenly in all directions.

Quad Light

Simulates light from an area source (a quadrilateral, specified by four vertices). It can be used to model light from an extended source (fluorescent strip lights) or in some circumstances from a window.

The light portal should be oriented so that it is pointing in through the window as indicated below:

_{Light portal pointing inwards outside window}

Skydome Light

This simulates light from a sphere or dome above the scene, representing the sky. It can also be used with high dynamic range (HDR) images to perform image-based environment lighting. This is the node that is typically used for lighting exterior scenes. The skydome_light has a texturable color slot so that you can map a texture to be used for IBL.

Note:

Simply adding an Environment Map automatically enables a skydome_light with no other input required. The skydome_light and background shader is constructed under the hood, and no extra light creation is required.

Spot Light

This simulates light from a spot_light, as a cone of light from the position of the light toward the point it is pointed at.

Light Filters

Light Filter Modifiers

Light Filters are available in MAXtoA as Light Modifiers. They are available when an Arnold light is selected:

Modifiers give you the ability to copy and paste your light filter onto other lights, including instancing the modifiers to multiple lights. You can apply modifiers to Group objects containing lights by using Copy and Paste from a single light onto the Group object. The modifier is then instanced to all lights in the group, and controllable from the top-level group object. The four built-in light filters are included as separate modifiers: decay, barndoor, light_blocker, and gobo (also known as Projection). The fifth option, the 'Arnold Light Filter' modifier, allows you to place a custom light filter shader into the modifier:

_{Arnold decay filter Modifier added to Arnold Light}

Barndoor

This light filter can only be used with spot lights. Barn doors are opaque moving panels attached to the sides of the light's opening. They are typically used in theatrical and film lighting for additional control over the shape of the light beam.

_{The barndoor filter's parameters}

Blocker

Light blockers give flexibility to the lighting TD. They can be used as an artificial method of masking light in a scene without the overhead of adding additional geometry. Used carefully, they provide a degree of artistic freedom, allowing you to define the light boundaries in non-physical ways.

Decay

This filter can be added to all Arnold lights. This is where you will specify the attenuation ranges. All lights in Arnold use a physically-based falloff by default, but the light_decay filter can be used to adjust the falloff for artistic purposes.

Gobo

The gobo filter can only be used with spot lights. In theatrical stage lighting, a gobo (or "cookie," slang for Cucoloris ) is a thin sheet of metal with holes used to break up the light beam into an irregular, more natural pattern such as tree leaves, etc.