Table of Contents

This page provides information on the Light Meter utility.


The VRayLightMeter helper is an aid for evaluating how a scene is illuminated. It is intended to simulate the use of a real-life light meter used in photography and film production.

The VRayLightMeter helper is a grid placed in the scene to gather information about the lighting in the grid's location. After creating and positioning the grid and setting parameters, click Calculate to calculate the lighting. The lighting information can be displayed in the viewport as colors and text on the grid representing different levels of light, and can also be saved in text form to a CSV file.

The information presented by the VRayLightMeter does not change or otherwise affect the lighting in the scene; it only reports on it. This helper is intended to provide information so you can make adjustments to the scene's lighting at your own discretion.

UI Path: 

||V-Ray menu|| > Create Helpers > V-Ray Light Meter

||Create menu|| > Helpers > V-Ray > V-Ray Light Meter > Click and drag in viewport

||Command panel|| > Create tab > Helpers > VRay category > VRayLightMeter button > Click and drag in viewport


Active – Enables or disables the VRayLightMeter helper.


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

Width – Width of the VRayLightMeter.  

Length – Length of the  VRayLightMeter.  

Width segs – Resolution of the VRayLightMeter in the X direction.

Length segs – Resolution of the VRayLightMeter in the Y direction.  


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

Pseudo Colors – When enabled, the VRayLightMeter displays 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. 
– Specifies the minimum illumination displayed in the viewport in lux. 
 – Specifies the maximum illumination displayed in the viewport in lux.  

Measured values – Specifies which part of the illumination in the scene is measured:  

Total illuminance – The total illuminance is measured, which 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. 
Day light factor
 – Calculates the illumination coming from the sky.  

Error Tolerance – Controls the precision of the VRayLightMeter. Higher values are faster to calculate but may appear noisy. 

Calculate – Press this button to calculate the measured values at light meter helper's grid points.  

Save to CSV file – Saves the result in a .csv file.

MaxScript Methods

The following methods of the VRayLightMeter object are accessible from MaxScript.

VRayLightMeter MethodDescription


Calculates the values along the light meter grid.
saveCSV<filename>Saves the values from the grid into the specified text file, in CSV (comma-separated values) format.


  • The VRayLightMeter helper is based on the texture baking and render elements functionality of the V-Ray renderer.
  • The VRayLightMeter helper uses Brute Force + Light Cache GI to calculate the measured values regardless of the GI engine selected, and regardless of whether GI is enabled in the scene, thus making it accurate and faster.
  • For more information on the VRayLightMeter and comparison cases, see the Lighting Analysis with V-Ray page. 
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