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

 

Overview


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

 

Dimensions 


 

 

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. 



Preview


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 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. 

 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.



Actions


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

Calculate – Hitting this button calculates 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


VRayLightMeter:

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

vrayLightMeterCalculate("VrayLightMeterShapeX");

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).

 

 

 

 

Notes


  • 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.