This page describes the use of V-Ray photometric lights.
Overview
Photometric lights utilize an .ies file which contains the distribution profile for the light. An .ies file contains complete specifications of a real world light bulb or tube including the shape of the light's cone and the steepness of the light's falloff. Such files are usually provided by the manufacturer of the real-world bulb, and the information in those files, gathered through lab experiments, is extremely accurate in its representation of the light source. By loading an .ies file, the light's properties are recreated within 3ds Max and used by V-Ray during rendering.
IES lights are particularly useful for architectural interior renderings, where it can be important to show the actual result of using specific man-made light sources in the scene.
While 3ds Max has standard photometric lights, V-Ray photometric lights are optimized to render faster in V-Ray.
||V-Ray Toolbar|| > V-Ray IES Light button > Click and drag in a viewport
||V-Ray menu|| > Create > Lights > V-Ray IES Light
||Create menu|| > Lights > V-Ray > V-Ray IES Light > click and drag in a viewport
||Command panel|| > Create tab > Lights > Choose V-Ray from dropdown > VRayIES > Click and drag in a viewport
You can also create a VRayIES object with a light profile loaded in it by dragging and dropping an .ies file directly in your active viewport.
Image courtesy of Sonny Ferian
Visualizing IES Profiles
The properties of an IES file can be visualized with Photometric Viewer software, which you can easily find online. Visually, the IES profile uses a graphed curve to show the shape and intensity of the light's emission. Depending on the software used, you might also be able to render a grayscale representation of how the light will look in a scene. Using a Photometric Viewer will help you better understand how the IES files you are using will affect your scene's lighting.
The graph below shows the IES profile of a typical bollard or post light, a type of light commonly used in architectural outdoor scenes. The rendered thumbnail is shown as an inset.
General
Enabled – Turns the VRayIES light on and off.
Targeted – Makes the VRayIES targeted.
IES file (button) – Specifies the .ies file that defines the light profile.
Intensity and color
Intensity value – Specifies the strength of the light.
Intensity type – Specifies the units for light strength:
Power (lm) – The Intensity value is considered in lumens.
Intensity (cd) – The Intensity value is considered in candela
Override intensity – Allows you to choose how the IES light source intensity is overridden by the Intensity value parameter.
Rescale – The IES file's default global light intensity is multiplied, so it matches the user's defined light intensity.
Replace – The IES file's default global light intensity is recalculated from the light source distribution and then multiplied to match the user's defined light intensity.
You may get wrong results using the Rescale option compared to the Replace one, if the IES file's default global intensity is incorrect for the given light source distribution.
Color mode – Specifies the mode in which the color of the light is determined:
Color – The light color is directly specified by the Color parameter.
Temperature – The light color temperature (in Kelvin) is specified by the Temperature parameter.
Color – Specifies the color of the light.
Color temperature – Specifies the light color temperature in Kelvin.
IES override
Rotation X/Y/Z – Rotates the light shape in relation to the target.
Override shape – When enabled, the light profile within the .ies file is ignored. The Shape parameter defines light shape for calculating shadow softness. Sharp shadows are generated with the point type.
Shape – Specifies a shape (and its orientation) for the VRayIES light when Override shape is enabled. Some shapes (shown below) enable additional options for size. See the Shape example below.
- point
- rectangle
- circle
- sphere
- vertical cylinder
- horizontal cylinder (length)
- horizontal cylinder (width)
- ellipse (length)
- ellipse (width)
- ellipsoid (length)
- ellipsoid (width)
Height – Specifies the height for applicable light Shape types.
Width – Specifies the width for applicable light Shape types.
Length – Specifies the length for applicable light Shape types.
Diameter – Specifies the diameter for applicable light Shape types.
Options
Exclude... – This button brings up the include/exclude list which allows users to exclude objects from light's illumination and shadow casting.
Use light shape – Determines whether and how the shape of the light is taken into consideration during the calculation of shadows and illumination.
No – The light shape is not considered for illumination and the light is going to generate sharp shadows.
For shadows – The light shape is considered only for the generation of soft shadows. The illumination is not affected by the light shape (i.e. it behaves as a point light).
For illumination and shadows – The light shape is considered for the calculation of the illumination and shadows.
Cast shadows – When enabled (the default), the light casts shadows. Turn this option off to disable shadow casting for the light.
Affect diffuse – Determines whether the light is affecting the diffuse properties of the materials.
Diffuse contribution – A multiplier for controlling the light's contribution to the diffuse illumination.
Affect specular – Determines whether the light is affecting the specular part of the materials.
Specular contribution – A multiplier for controlling the light's contribution to the specular reflection.
Affect atmospherics - When enabled, the light influences the atmospheric effects in the scene.
Atmospherics contribution - Determines the amount of influence the light has on the atmospheric effects.
Area speculars – When disabled, the particular light is rendered as a point light in the specular reflections
Sampling
Shadow bias – Moves the shadow toward or away from the shadow-casting object (or objects). If the Bias value is too low, shadows can "leak" through places they shouldn't, produce moire patterns, or make out-of-place dark areas on meshes. If Bias is too high, shadows can "detach" from an object. If the Bias value is too extreme in either direction, shadows might not be rendered at all.
Cutoff – Specifies a threshold for the light intensity, below which the light is not computed. This can be useful in scenes with many lights, where you want to limit the effect of the lights to some distance around them. Larger values cut away more from the light; lower values make the light range larger. If you specify 0.0, the light is calculated for all surfaces. This parameter is not available when the renderer is set to GPU.
Decay
Near on – Toggles near decay on and off. The decay parameters determine how the light fades in and out. The decay Near determines how light "fades in". The light isn't at its maximum value at its source, but instead gradually increases until it reaches the Near end. The decay Far determines how light "fades out". The light isn't at its maximum value at its end, but instead gradually decreases after the Far start. See the Near examples below for more information.
Near start – Determines where the "fade in" starts. If set at 0, light won't be visible directly in front of the light source, but will instead "fade in" from it.
Near end – Determines where the "fade in" ends. After this threshold, the light is at its full value.
Far on – Toggles far decay on and off. See the Far examples below for more information.
Far start – Determines where the "fade off" starts.
Far end – Determines where the light reaches a value of 0, i.e. completely fades off.
Viewport
Show distribution – Shows the IES profile distribution as a mesh around the light source in the viewports.
Icon text – Turns the viewport icon text on or off.
Viewport wire color – Changes the wireframe color of the light in the viewport. This is useful to visually recognize groups of lights from one another.
Enable viewport shading – When enabled, the effect of the VRayIES light is visible in the viewport.
Examples
Example: Shape
This example shows how light is affected by the different shapes of the IES Light. Circle and Sphere shapes examples are also compared with different diameters - 1.0 and 10.0.
Circle, Diameter = 1.0
Circle, Diameter = 10.0
Default shape From the IES light
Point
Sphere, Diameter = 1.0
Sphere, Diameter = 10.0
Example: Near Decay Start
This example shows the variances achieved by changing the Near decay start parameters only.
Near decay start 10, Near decay end 60
Near decay start 30, Near decay end 60
Near decay start 50, Near decay end 60
Example: Near Decay End
This example shows the variances achieved by changing the Near decay end parameters only.
Near decay start 0, Near decay end 10
Near decay start 0, Near decay end 30
Near decay start 0, Near decay end 50
Example: Far Decay Start
This example shows the variances achieved by changing the Far decay start parameters only.
Far decay start 10, Far decay end 60
Far decay start 30, Far decay end 60
Far decay start 50, Far decay end 60
Example: Far Decay End
This example shows the variances achieved by changing the Far decay end parameters only.
Far decay start 60, Far decay end 60
Far decay start 60, Far decay end 100
Far decay start 60, Far decay end 120
Example: Near and Far Decay
This example shows some artistic lighting results achieved by using both Near and Far decay options.
Near decay start 0, Near decay end 15, Far decay start 30, Far decay end 60
Near decay start 20, Near decay end 35, Far decay start 40, Far decay end 55
Near decay start 30, Near decay end 60, Far decay start 90, Far decay end 120