Table of Contents

This page provides information on the V-Ray Light Analysis Render Element.


The Light Analysis Render Element provides visual representation of the lighting intensity in the rendered frame. It collects Illuminance and Luminance information during rendering and maps it as color gradient or a grid of measured values onto the frame.

Illuminance measures the amount of light on a surface per unit area in lux. It shows how bright your surface is. Luminous intensity measures the brightness of a light source in candela.

 The collected lighting information is stored in internally generated Illuminance and Luminance render channels using the respective light measurement units. Then, the Lighting Analysis Render Element simply takes the information from the selected channel and applies display modifications to it. This makes it readable with a naked eye when overlaid onto the final render as a post-effect.

During the render, the lighting analysis may display some approximation to the false-color image, but it should not be interpreted as being the final result. Once rendered, the VRayLightingAnalysis parameters can be adjusted further and its representation can be updated without the need to re-render.



VRayVFB – When enabled, the render element appears in the V-Ray Virtual Frame Buffer.

Quantity – Chooses which lighting information to be analyzed.

Illuminance (lx) – Uses the Illuminance of the rendered frame in lux. 
Luminance (cd) 
– Uses the Luminance of the rendered frame in candelas.

Min value – Specifies which values are mapped to blue. 

Max value – Specifies which values are mapped to red.

Scale – Specifies how values are mapped to colors onto the frame.

Linear – The colors are mapped in linear scale. 

Logarithmic – The colors are mapped in logarithmic scale. 

Display – Specifies the analyzed data display mode.

False colors – Fills the frame with a gradient ranging from blue (low values) to red (high values). For the out of range values uses respectively black and white.
Grid overlay 
– Displays the values at distinct grid points over the frame. They use the same grading colors.

Grid horizontal/vertical spacing – Specifies the horizontal/vertical space in pixels between two numeric points on the grid.

Fade background image – (active only if Display is in Grid overlay mode) When enabled, it fades the rendered image, so that the grid values would be more visible. 

Draw legend – When enabled, shows a legend of the false colors at the bottom of the render. 

Update button – Updates the mapped information over the frame if the parameters are changed. V-Ray Frame Buffer must be used for the updates to have effect.



This example shows the False Colors and Grid Overlay Display modes.

Light Analysis Render showing Illuminance with False Colors display

Light Analysis Render showing Luminance with False Colors display 

Light Analysis Render showing Illuminance with Grid Overlay display


  • Illuminance values shown over glass and mirror objects represent illuminance of the glass or mirror surface and not on the surfaces seen through the glass or mirror. The result can appear noisy or be shown as a zero value. The reason is that such materials do not reflect light diffusely and V-Ray computes the illuminance values with low precision or may skip illuminance calculations completely. To ensure correct results, it is recommended to use the default V-Ray GI settings, with optionally increased Light cache subdivs (e.g. 2000) and higher Light cache retrace threshold (e.g. 4.0).
  • For more information on the Lighting Analysis tools and comparison cases, see the Lighting Analysis with V-Ray page.