Dome Light Options
The VRayLight is a V-Ray specific light source plugin that can be used to create physically accurate area lights.
The size of a V-Ray light is controlled through the Area tab of the Light node attached to the VRayLight node. This is similar to the way the size of standard Softimage lights is controlled. The only difference is that just some of the parameters here are considered and their meaning depends on the Type of the light. The Dome light is not affected by the settings here as the illumination it creates is not dependent on the size of the light. To change the size of V-Ray lights you need to adjust the settings in Area Transformation -> Scaling
X - this parameter controls the radius of the Sphere light and the size along the local X coordinate of the Plane light. It does not affect the Dome light.
Y - this parameter controls the size along the local Y coordinate of the Plane light. It does not affect the Sphere or Dome lights
On - turns the VRayLight on and off
Type - specifies the shape of the light:
Plane - the VRayLight has the shape of a planar rectangle.
Sphere - the VRayLight has the shape of a sphere.
Dome - the VRayLight acts like the SkyLight object in 3ds Max. The light is coming from a (hemi)spherical dome above the z-axis of the light.
Units - allows choosing the light units. Using correct units is essential when you work with the VRayPhysicalCamera. The light will automatically take the scene units scale into consideration to produce the correct result for the scale you are working with. The possible values are:
Default (image) - the color and multiplier directly determine the visible color of the light without any conversion. The light surface will appear with the given color in the final image when seen directly by the camera (assuming there is no color mapping involved).
Luminous power (lm) - total emitted visible light power measured in lumens. When this setting is used, the intensity of the light will not depend on its size. A typical 100W incandescent light bulb emits about 1500 lumens of light.
Luminance (lm/m^2/sr) - visible light surface power measured in lumens per square meter per steradian. When this setting is used, the intensity of the light depends on its size.
Radiant power (W) - total emitted visible light power measured in watts. When using this setting, the intensity of the light does not depend on its size. Keep in mind that this is not the same as the electric power consumed by a light bulb for example. A typical 100W light bulb only emits between 2 and 3 watts as visible light.
Radiance (W/m²/sr) - visible light surface power measured in watts per square meter per steradian. When this setting is used, the intensity of the light depends on its size.
Mode - allows you to select the mode in which the color of the light will be 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 when the Mode parameter is set to Color. When using photometric units, this color is normalized so that only the color hue is used, whereas the light intensity is determined by the light Multiplier. This parameter can also be textured if the light Type is set to Plane.
Temperature - specifies the color of the light in degrees Kelvin when the Mode parameter is set to Temperature
Multiplier - multiplier for the light color; this is also the light intensity in the units chosen by the Intensity units parameter.
Tex Adaptive - when this option is checked V-Ray will use importance sampling on the texture in order to produce better shadows.
Texture resolution - specifies the resolution at which the texture is sampled when the Tex Adaptive option is checked.
On - when on (the default), the light casts shadows. Turn this option off to disable shadow casting for the light.
Shadow bias - 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 making 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.
Color - allows you to specify a tint for the shadows cast by this light
Subdivs - this value controls the number of samples V-Ray takes to compute lighting. Lower values mean more noisy results, but will render faster. Higher values produce smoother results but take more time. Note that the actual number of samples also depends on the DMC Sampler settings.
Photon subdivs - this value is used by V-Ray when calculating the Global Photon Map. Lower values mean more noisy results, but will render
faster. Higher values produce smoother results but take more time.
Diffuse multiplier - a multiplier for the diffuse photons.
Caustics subdivs - this value is used by V-Ray when calculating Caustics. Lower values mean more noisy results, but will render faster. Higher values produce smoother results but take more time.
Caustics multiplier -this value is a multiplier for the generated caustics by the selected light. Note that this multiplier is cumulative - it does not override the multiplier in the Caustics render roll-out section.
Override motion blur samples - allows you to overide the default number of samples that will be used to sample the current light for motion blur.
Motion blur samples - when the Override motion blur samples is enabled this value will be used when sampling the motion blur created by the current light.
Double-sided - when the light is a planar light source this option controls whether light is beamed from both sides of the plane. This field has no effect for Sphere or Dome light sources.
Invisible - this setting controls whether the shape of the VRayLight source is visible in the render result. When this option is turned off the source is rendered in the current light color. Otherwise it is not visible in the scene. Note that this option only affects the visibility of the light when seen directly by the camera or through refractions. The visibility of the light with respect to reflections is controlled by the Affect specular option.
Ignore light normals - normally, the surface of the source emits light equally in all directions. When this option is off, more light is emitted in the direction of the source surface normal.
No decay - normally the light intensity is inversely proportional to the square of the distance from the light (surfaces that are farther from the light are darker than surfaces which are closer to the light). When this option is on the intensity will not decay with distance.
Skylight portal - when this option is on, the Color and Multiplier parameters are ignored; instead the light will take its intensity from the environment behind it.
Simple Skylight portal - this option is only enabled if the Skylight Portal option is on. It tells the VRayLight that there is nothing of interest behind the light itself, and so the environment color can be used directly. Normally, the portal light takes its color from whatever objects are behind it. In order to do this, the light traces additional rays, which may slow down the rendering. Turning this option on makes the rendering of portal lights faster.
Store with irradiance map - when this option is on and GI calculation is set to Irradiance map V-Ray will calculate the effects of the VRayLight and store them in the irradiance map. The result is that the irradiance map is computed more slowly but the rendering takes less time. You can also save the irradiance map and reuse it later.
Affect diffuse - this determines whether the light is affecting the diffuse properties of the materials.
Affect specular - this determines whether the light is affecting the specular of the materials.
Affect reflections - this determines whether the light will appear in reflections of materials.
Diffuse contribution - a multiplier for the effect of the light on the diffuse.
Specular contribution - a multiplier for the effect of the light on the specular.
Cut-off threshold - this parameter specifies a threshold for the light intensity, below which the light will not be 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 will be calculated for all surfaces.
Dome light options
Spherical (full dome) - when on, this option causes the dome light to cover the entire sphere around the scene. When off (the default), the light covers a hemisphere only.
The options here allow you to put a limit to the distance at which shadow rays are going to be traced in order to save render time.
Mode - specifies the meaning of the Ray Dist parameter
None - the Ray Dist option is disabled.
From GI Settings - the Ray Dist value is determined by the Ray Distance parameter in the GI settings
Explicit - the Ray Dist value is determined by the user.
Ray Dist - specifies the maximum distance to which shadow rays are going to be traced when the Mode is set to Explicit..
Use texture - when the Rectangle, Dome or Mesh light type is used, this tells the light to use a texture for the light surface. If there are surfaces which are close to a texture-mapped light, it is best to have GI enabled. This allows V-Ray to use combined direct and indirect sampling for the light, reducing the noise for surfaces close to the light.
Adaptive - when this option is on V-Ray will adjust the number of samples taken for different parts of the texture depending on their brightness.
Texture - specifies the texture to use. The texture intensity is also affected by the Multiplier of the light. To properly map the environmental texture a VRayEnvImage must be load here.
Resolution - specifies the resolution at which the texture is re sampled for importance sampling.
Target radius - for the Dome light, defines a sphere around the light icon where photons are being shot when photon-mapped caustics or the global photon map are used.
Emit radius - for the Dome light, defines a sphere around the light icon from which photons are being shot towards the target radius area.