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 maps Illuminance and Luminance information as color gradient or a grid of measured values onto the frame.
The Illuminance and Luminance channels are internally created during rendering. Once rendered, the parameters can be adjusted and the analysis can be updated without the need to re-render.

The VRayLightingAnalysis render element is a post-effect and is only updated once the rendering is complete. During the render, the VRayLightingAnalysis may display some approximation to the false-color image, but it should not be interpreted as being the final result.


UI Path

||Render Setup window|| > Render Elements tab > Add button > VRayLightingAnalysis


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

quantity – Choose which lighting information to be analysed.

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 analysed 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 – This option is 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.



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 Next page.