The V-Ray Light Mesh can create light sources that have volume and shape without the need to use self illuminated objects and global illumination.
If the Light Mesh is close to other surfaces in the scene, it is best to use it with GI enabled so V-Ray can use combined direct and GI sampling of the mesh light. Without GI, the light might produce noisy results for surfaces that are very close to it.
To create a V-Ray Mesh Light, use the button in the V-Ray Lights tab. If a mesh is not currently selected, Rhino will prompt the user to select the mesh before creating the mesh light.
Right clicking the V-Ray Mesh Light button enables the user to release or remove the Mesh Light from the original mesh.
UI Path: V-Ray Toolbar > V-Ray Lights tab > V-Ray Mesh Light
Enabled () – Determines whether or not the Mesh Light will emit light in the scene.
Color/Texture – The color of the light. When using photometric units, this color is normalized so that only the color hue is used, whereas the light intensity is determined by the Intensity Multiplier. Specifies a texture file for the Mesh Light. Texture is not supported by V-Ray GPU render.
Intensity – Specifies the strength of the light.
Units – Specifies the light unit of measurement. Using correct units is essential when working with the VRayPhysicalCamera. The light will automatically take the scene units scale into consideration to produce the correct result for the scale being worked in.
Default (Scalar) – 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.
Luminous Power (Lumens) – Total emitted visible light power measured in lumens. 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. The intensity of the light depends on its size.
Radiant Power (W) – Total emitted visible light power measured in watts. The intensity of the light does not depend on its size. 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/m^2/sr) – Visible light surface power measured in watts per square meter per steradian. The intensity of the light depends on its size
Invisible – When enabled, the shape of the light source will not be visible in the render result. When disabled, the source is rendered in the current light color. This 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.
Double Sided – When enabled, light will be emitted from back-facing polygons of the mesh as well.
Affect Diffuse – When enabled, the light affects the diffuse properties of the materials.
Affect Specular – When enabled, the light affects the specular of the materials.
Affect Reflections – When enabled, the light appears in reflections of materials.
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 enabled, the intensity will not decay with distance.
Shadows – When enabled (the default), the light casts shadows. When disabled, the light does not cast shadows.
Caustic Subdivs – Used by V-Ray when calculating Caustics. Lower values produce noisy results but will render faster. Higher values produce smoother results but take more time.