This page describes the V-Ray Light Meter and its use.


Page Contents



The VRayLightMeter node evaluates how a scene is illuminated at a given time during the day or how it is affected by different light sources. The information can be displayed in the viewport or saved to a CSV file.


UI Path: ||V-Ray Shelf|| > Create VRayLightMeter button





The options in this group allow us to specify the dimensions of the light meter tool and its resolution - the number of points at which the illumination will be measured. 

Width – the width of the VRayLightMeter. 

Length – the length of the VRayLightMeter. 

Width segs – the resolution of the VRayLightMeter in the x direction.

Length segs – the resolution of the VRayLightMeter in the z direction. 


The settings in this group control the way the illumination information is represented in the view port. 

Viewport Orientation – enables or disables the preview of the direction from which the light is coming.

Viewport Text – enables or disables the preview of the actual values of the illumination for each point.

Viewport Colors – when enabled the VRayLightMeter will display a gradient to illustrate the variation in the illumination. 

Logarithmic – changes the illumination scale to Logarithmic for the purposes of displaying it in the viewport . This is useful when there is a great variation in the illumination.
Min – specifies the minimum illumination displayed in the viewport in lux.
Max – specifies the maximum illumination displayed in the viewport in lux. 


Measured values – specifies which part of the illumination in the scene will be measured: 

Total illuminance – the total illuminance will be measured - this includes direct light, GI, and light coming from the environment.
Direct illuminance – calculates only the illumination from direct lighting.
Indirect illuminance – calculates only the effect of the indirect illumination.


GI Subdivs – number of GI subdivs used for calculating the measured values.

Calculate – hitting this button will calculate the measured values at the grid points of the light meter helper. 

Save to CSV file – this button allows you to save the result in a .csv file.



Example: VRayLightMeter

The following example shows how VrayLightMeter measures the illuminance from two lights.

VRayLightRect – default settings with Intensity multiplier of 90

VRayLightSphere: default settings


Witdth = 24

Lenght = 24

Witdth = 8

Lenght = 8

Viewport Orientation: ON

Viewport Text: ON

Viewport Colors: ON

Min = 0

Max = 1000

Measured Value: Total Illuminance





MEL Script Methods

The following methods of the VRayLightMeter node are accessible from the Script Editor.

VRayLightMeter MethodDescription


Calculates the values along the light meter grid.
vrayLightMeterSaveToCSV("VrayLightMeterShapeX", "path/filename.csv");Saves the values from the grid into the specified text file, in CSV (comma separated values) format.
vray getLightmeterMaxValue <NODE NAME - STRING> [direct|gi|total]Returns the maximum value of a lightmeter (for Direct/GI/Total light).






  • The VRayLightMeter node is based on the texture baking and render elements functionality of the V-Ray renderer.
  • The VRayLightMeter node uses brute force GI with user selected GI Subdivs and 100 Bounces to calculate the measured values.